diff --git a/lib_com/options.h b/lib_com/options.h
index 4ad75910ccfd9e2908872e25569f51fc7310c2d8..e2543337aa061e9ea20e66049a42f81efd36c405 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -117,6 +117,9 @@
 #define NONBE_FIX_ISM_XOVER_BR                          /* FhG: issue 1072: select OSBA coding method depending on number of object and bitrate */
 #define FIX_1053_REVERB_RECONFIGURATION                 /* Philips: issue 1053: fix for dynamic switching of acoustic environment */
 #define CONF_DISTATT                                    /* Eri: Make distance attenuation configurable */
+
+#define ISSUE_1866_replace_overflow_libdec              /* FhG: BE - Replace BASOPoverflow operators all over the lib_dec module if Overflow result is not used*/
+
 #define FIX_1068_ASAN_IN_MC_2_BINAURAL_ROOM_IR          /* issue 1068 : Memory leak in MC to BINAURAL_ROOM decoding with bitrate switching*/
 #define NONBE_FIX_1052_SBA_EXT                          /* Dlb: SBA external output support */
 #define NONBE_FIX_MC_LFE_LPF                                  /* Dlb: Adding the LFE LPF filter back for MC content. */
diff --git a/lib_dec/FEC_HQ_core_fx.c b/lib_dec/FEC_HQ_core_fx.c
index 1be7453ab9492386fa762903658b5ff6c66921bc..06028d6011b674a6cb68ecc935db3a6c06afea06 100644
--- a/lib_dec/FEC_HQ_core_fx.c
+++ b/lib_dec/FEC_HQ_core_fx.c
@@ -43,7 +43,7 @@ static void Regression_Anal_fx(
     Word32 L_tmp1, L_tmp2;
     Word16 aindex_fx[MAX_PGF + 1]; // Q0
     Word32 b_p_fx[MAX_PGF + 1];    // Q10
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -80,8 +80,8 @@ static void Regression_Anal_fx(
     {
         b_p_fx[0] = L_add( b_p_fx[0], L_shr( values_fx[i], 2 ) ); /*10 */
         move32();
-#ifdef ISSUE_1796_replace_shl_o
-        b_p_fx[1] = L_add( b_p_fx[1], Mult_32_16( values_fx[i], shl_sat( sub( num_pgf, i ), 13 ) ) ); /*10 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        b_p_fx[1] = L_add( b_p_fx[1], Mult_32_16( values_fx[i], shl_sat( sub( num_pgf, i ), 13 ) ) ); /*10 */ //??sat
 #else
         b_p_fx[1] = L_add( b_p_fx[1], Mult_32_16( values_fx[i], shl_o( sub( num_pgf, i ), 13, &Overflow ) ) ); /*10 */
 #endif
@@ -168,7 +168,7 @@ void HQ_FEC_processing_fx(
     Word16 energy_diff_fx; // Q10
     HQ_NBFEC_HANDLE hHQ_nbfec;
     HQ_DEC_HANDLE hHQ_core;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -390,8 +390,8 @@ void HQ_FEC_processing_fx(
 
                 FOR( j = 0; j < Num_bands_p[i]; j++ )
                 {
-#ifdef ISSUE_1796_replace_shl_o
-                    hHQ_nbfec->Norm_gain_fx[k] = shl_sat( tmp_fx, 1 );
+#ifdef ISSUE_1866_replace_overflow_libdec
+                    hHQ_nbfec->Norm_gain_fx[k] = shl_sat( tmp_fx, 1 ); //??sat
 #else
                     hHQ_nbfec->Norm_gain_fx[k] = shl_o( tmp_fx, 1, &Overflow );
 #endif
@@ -449,9 +449,11 @@ void ivas_HQ_FEC_Mem_update_fx(
     HQ_DEC_HANDLE hHQ_core;
     hHQ_nbfec = st_fx->hHQ_nbfec;
     hHQ_core = st_fx->hHQ_core;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     move32(); // for tmp_energy_fx
     IF( EQ_16( output_frame, L_FRAME8k ) )
@@ -530,8 +532,8 @@ void ivas_HQ_FEC_Mem_update_fx(
                 L_tmp = L_add( L_tmp, L_shr( normq_fx[k], 3 ) ); /*11*/
                 k = add( k, 1 );
             }
-#ifdef ISSUE_1796_replace_shl_o
-            tmp_fx = shl_sat( inv_tbl_fx[Num_bands_p[i]], 1 ); /*16*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+            tmp_fx = shl_sat( inv_tbl_fx[Num_bands_p[i]], 1 ); /*16*/ //??sat
 #else
             tmp_fx = shl_o( inv_tbl_fx[Num_bands_p[i]], 1, &Overflow ); /*16*/
 #endif
@@ -654,7 +656,11 @@ void ivas_HQ_FEC_Mem_update_fx(
             exp2 = norm_l( hHQ_nbfec->ynrm_values_fx[i][0] );
             tmp_fx = div_s( extract_h( L_shl( en_high_fx[i], exp1 ) ), extract_h( L_shl( hHQ_nbfec->ynrm_values_fx[i][0], exp2 ) ) );
             exp = add( 15, sub( exp1, exp2 ) );
+#ifdef ISSUE_1866_replace_overflow_libdec
+            *mean_en_high_fx = add_sat( *mean_en_high_fx, shr_sat( tmp_fx, sub( exp, 5 ) ) ); //??sat
+#else
             *mean_en_high_fx = add_o( *mean_en_high_fx, shr_sat( tmp_fx, sub( exp, 5 ) ), &Overflow );
+#endif
             move16();
         }
         *mean_en_high_fx = mult( *mean_en_high_fx, inv_tbl_fx[sub( num_Sb, k )] );
@@ -736,9 +742,11 @@ void HQ_FEC_Mem_update_fx(
     HQ_DEC_HANDLE hHQ_core;
     hHQ_nbfec = st_fx->hHQ_nbfec;
     hHQ_core = st_fx->hHQ_core;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     move32(); // tmp_energy_fx
 
@@ -819,8 +827,8 @@ void HQ_FEC_Mem_update_fx(
                 L_tmp = L_add( L_tmp, L_shr( normq_fx[k], 3 ) ); /*11*/
                 k = add( k, 1 );
             }
-#ifdef ISSUE_1796_replace_shl_o
-            tmp_fx = shl_sat( inv_tbl_fx[Num_bands_p[i]], 1 ); /*16*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+            tmp_fx = shl_sat( inv_tbl_fx[Num_bands_p[i]], 1 ); /*16*/ //??sat
 #else
             tmp_fx = shl_o( inv_tbl_fx[Num_bands_p[i]], 1, &Overflow ); /*16*/
 #endif
@@ -944,7 +952,11 @@ void HQ_FEC_Mem_update_fx(
             exp2 = norm_l( hHQ_nbfec->ynrm_values_fx[i][0] );
             tmp_fx = div_s( extract_h( L_shl( en_high_fx[i], exp1 ) ), extract_h( L_shl( hHQ_nbfec->ynrm_values_fx[i][0], exp2 ) ) );
             exp = add( 15, sub( exp1, exp2 ) );
+#ifdef ISSUE_1866_replace_overflow_libdec
+            *mean_en_high_fx = add_sat( *mean_en_high_fx, shr_sat( tmp_fx, sub( exp, 5 ) ) ); //??sat
+#else
             *mean_en_high_fx = add_o( *mean_en_high_fx, shr_sat( tmp_fx, sub( exp, 5 ) ), &Overflow );
+#endif
             move16();
         }
         *mean_en_high_fx = mult( *mean_en_high_fx, inv_tbl_fx[sub( num_Sb, k )] );
@@ -1015,7 +1027,7 @@ static Word16 find_best_delay_fx(
     Word32 min_sq_cross_fx, min_corr_fx;
     Word32 accA_fx, accB_fx;
     Word32 Rxy_fx[MAXDELAY_FEC], Ryy_fx[MAXDELAY_FEC];
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -1086,10 +1098,10 @@ static Word16 find_best_delay_fx(
         L_tmp1 = L_shl( min_sq_cross_fx, exp1 );
         L_tmp2 = L_shl( min_corr_fx, exp2 );
         tmp = div_s( extract_h( L_tmp1 ), extract_h( L_tmp2 ) ); /*15 + exp1 - exp2 */
-#ifdef ISSUE_1796_replace_shl_o
-        tmp = shl_sat( tmp, sub( exp2, add( exp1, 1 ) ) ); /*14 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        tmp = shl_sat( tmp, sub( exp2, add( exp1, 1 ) ) ); /*14 */ //??sat
 #else
-        tmp = shl_o( tmp, sub( exp2, add( exp1, 1 ) ), &Overflow );     /*14 */
+        tmp = shl_o( tmp, sub( exp2, add( exp1, 1 ) ), &Overflow ); /*14 */
 #endif
     }
 
diff --git a/lib_dec/FEC_HQ_phase_ecu_fx.c b/lib_dec/FEC_HQ_phase_ecu_fx.c
index 5cb2c99dc63be84a1a2f5c060d6206b5ef741c66..b145a3aaea8455a547601b33f8aad9e6e61984cb 100644
--- a/lib_dec/FEC_HQ_phase_ecu_fx.c
+++ b/lib_dec/FEC_HQ_phase_ecu_fx.c
@@ -2916,13 +2916,20 @@ static Word32 mult_32_32_q( const Word32 a, const Word32 b, const Word16 q )
 {
     Word32 hi;
     UWord32 lo;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
 #endif
+
     Mpy_32_32_ss( a, b, &hi, &lo );
 
     return L_or( L_shl_o( hi, sub( 32 - 1, q ), &Overflow ), L_lshr( (Word32) lo, add( q, 1 ) ) );
+#else
+    Mpy_32_32_ss( a, b, &hi, &lo );
+
+    return L_or( L_shl_sat( hi, sub( 32 - 1, q ) ), L_lshr( (Word32) lo, add( q, 1 ) ) ); //??sat
+#endif
 }
 
 static void fir_dwn_fx(
diff --git a/lib_dec/FEC_fx.c b/lib_dec/FEC_fx.c
index 78594558b78dae073e4c787fe15fec99d45478cd..4343c3edc7a32f90c4330b4fe896bf30516d658a 100644
--- a/lib_dec/FEC_fx.c
+++ b/lib_dec/FEC_fx.c
@@ -95,9 +95,11 @@ void FEC_exc_estim_fx(
     Word32 cond3;
     Word32 predPitchLag;
     GSC_DEC_HANDLE hGSCDec;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
+#endif
 #endif
     hGSCDec = st_fx->hGSCDec;
 
@@ -126,7 +128,7 @@ void FEC_exc_estim_fx(
 
         gainCNG = round_fx( L_shl( L_tmp, sub( exp, 12 ) ) ); /* In Q3 */
     }
-#ifdef ISSUE_1796_replace_shl_o
+#ifdef ISSUE_1866_replace_overflow_libdec
     tmp1 = shl_sat( st_fx->lp_gainc_fx, 1 );
 #else
     tmp1 = shl_o( st_fx->lp_gainc_fx, 1, &Overflow );
@@ -191,10 +193,10 @@ void FEC_exc_estim_fx(
     {
         test();
         test();
-#ifdef ISSUE_1796_replace_shl_o
-        IF( ( LT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR - 1], 6 ) ), shl_sat( mult( 29491, st_fx->bfi_pitch_fx ), 1 ) ) &&
-              GT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR - 1], 6 ) ), mult( 19661, st_fx->bfi_pitch_fx ) ) ) || /* last pitch coherent with the past  */
-            GE_16( st_fx->upd_cnt, MAX_UPD_CNT ) )                                                                                /* or last update too far in the past */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        IF( ( LT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR - 1], 6 ) ), shl_sat( mult( 29491, st_fx->bfi_pitch_fx ), 1 ) ) && //??sat
+              GT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR - 1], 6 ) ), mult( 19661, st_fx->bfi_pitch_fx ) ) ) ||             /* last pitch coherent with the past  */
+            GE_16( st_fx->upd_cnt, MAX_UPD_CNT ) )                                                                                            /* or last update too far in the past */
 #else
         IF( ( LT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR - 1], 6 ) ), shl_o( mult( 29491, st_fx->bfi_pitch_fx ), 1, &Overflow ) ) &&
               GT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR - 1], 6 ) ), mult( 19661, st_fx->bfi_pitch_fx ) ) ) || /* last pitch coherent with the past  */
@@ -210,10 +212,10 @@ void FEC_exc_estim_fx(
     {
         test();
         test();
-#ifdef ISSUE_1796_replace_shl_o
-        IF( ( LT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR16k - 1], 6 ) ), shl_sat( mult( 29491, st_fx->bfi_pitch_fx ), 1 ) ) &&
-              GT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR16k - 1], 6 ) ), mult( 19661, st_fx->bfi_pitch_fx ) ) ) || /* last pitch coherent with the past  */
-            GE_16( st_fx->upd_cnt, MAX_UPD_CNT ) )                                                                                   /* or last update too far in the past */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        IF( ( LT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR16k - 1], 6 ) ), shl_sat( mult( 29491, st_fx->bfi_pitch_fx ), 1 ) ) && //??sat
+              GT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR16k - 1], 6 ) ), mult( 19661, st_fx->bfi_pitch_fx ) ) ) ||             /* last pitch coherent with the past  */
+            GE_16( st_fx->upd_cnt, MAX_UPD_CNT ) )                                                                                               /* or last update too far in the past */
 #else
         IF( ( LT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR16k - 1], 6 ) ), shl_o( mult( 29491, st_fx->bfi_pitch_fx ), 1, &Overflow ) ) &&
               GT_16( round_fx( L_shl( st_fx->old_pitch_buf_fx[2 * NB_SUBFR16k - 1], 6 ) ), mult( 19661, st_fx->bfi_pitch_fx ) ) ) || /* last pitch coherent with the past  */
@@ -313,7 +315,11 @@ void FEC_exc_estim_fx(
         IF( LE_16( st_fx->nbLostCmpt, 1 ) )
         {
             /* if stable, do not decrease the energy, pitch_gain = 0 */
-            alpha = mac_ro( ( 1L << 16 ) * 2 * _ALPHA_U_FX, st_fx->stab_fac_fx, 32768 - 2 * _ALPHA_U_FX, &Overflow ); /*st_fx->stab_fac_fx in Q15*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+            alpha = mac_r_sat( ( 1L << 16 ) * 2 * _ALPHA_U_FX, st_fx->stab_fac_fx, 32768 - 2 * _ALPHA_U_FX ); /*st_fx->stab_fac_fx in Q15*/ //??sat
+#else
+            alpha = mac_ro( ( 1L << 16 ) * 2 * _ALPHA_U_FX, st_fx->stab_fac_fx, 32768 - 2 * _ALPHA_U_FX, &Overflow );                /*st_fx->stab_fac_fx in Q15*/
+#endif
         }
         ELSE IF( EQ_16( st_fx->nbLostCmpt, 2 ) )
         {
@@ -362,7 +368,11 @@ void FEC_exc_estim_fx(
             L_tmp = L_deposit_h( tmp );
             L_tmp = Isqrt_lc( L_tmp, &exp );
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+            gain = extract_h( L_shl_sat( L_tmp, exp ) ); //??sat
+#else
             gain = extract_h( L_shl_o( L_tmp, exp, &Overflow ) );
+#endif
 
             gain = s_min( gain, 32113 ); /*0.98 */
             gain = s_max( gain, 27853 ); /*0.85 */
@@ -768,7 +778,7 @@ static void pulseRes_preCalc( Word16 *cond1, Word16 *cond2, Word32 *cond3, Word1
 {
     Word16 tmp_pit, tmp_pit_e, tmp_frame, tmp_frame_e;
     Word32 tmp_pit2;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -782,8 +792,8 @@ static void pulseRes_preCalc( Word16 *cond1, Word16 *cond2, Word32 *cond3, Word1
     tmp_frame = sub( 32767 /*1.f Q15*/, tmp_frame ); /*Q15*/
     BASOP_SATURATE_WARNING_OFF_EVS
     /*To calc Q15 threshold, overflow may happen - do negation and compare with negated value to check also highest possible value*/
-#ifdef ISSUE_1796_replace_shl_o
-    tmp_pit = shl_sat( negate( tmp_pit ), tmp_pit_e );
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp_pit = shl_sat( negate( tmp_pit ), tmp_pit_e ); //??sat
 #else
     tmp_pit = shl_o( negate( tmp_pit ), tmp_pit_e, &Overflow );
 #endif
diff --git a/lib_dec/LD_music_post_filter_fx.c b/lib_dec/LD_music_post_filter_fx.c
index 4c3fa372892f8ac06b81c987492a58e36e01eb4c..eb1f5eca94442fdb95b4567c9115cc3d213d9df2 100644
--- a/lib_dec/LD_music_post_filter_fx.c
+++ b/lib_dec/LD_music_post_filter_fx.c
@@ -69,8 +69,10 @@ void LD_music_post_filter_fx(
     Word16 mant, exp1, s_ave, tmp16, old_tmp16;
     Word16 diff_sc;
     Word16 old_tmp16_1;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
+#endif
 #endif
     move16();
     move16();
@@ -186,7 +188,11 @@ void LD_music_post_filter_fx(
         FOR( k = j; k < mfreq_bindiv_LD[i] + j; k++ )
         {
             /*m_ave += lf_E[k];*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+            Ltmp = L_add_sat( lf_E[k], Ltmp ); /*2*Qdct+10*/ //??sat
+#else
             Ltmp = L_add_o( lf_E[k], Ltmp, &Overflow ); /*2*Qdct+10*/
+#endif
             max_val = L_max( max_val, lf_E[k] );
         }
         Ltmp_max = L_max( Ltmp_max, max_val ); /*2*Qdct+10*/
@@ -442,8 +448,10 @@ static void spectrum_mod_dct_fx(
     Word32 Lshift;
     Word32 dot5_scaled;
     const Word32 *Lpt2;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
+#endif
 #endif
 
     move16();
@@ -523,7 +531,11 @@ static void spectrum_mod_dct_fx(
 
     IF( music_flag != 0 ) /* prevent subtraction on clean speech */
     {
+#ifdef ISSUE_1866_replace_overflow_libdec
+        IF( LE_32( maxNoise, L_shl_sat( 10, scaling ) ) ) //??sat
+#else
         IF( LE_32( maxNoise, L_shl_o( 10, scaling, &Overflow ) ) )
+#endif
         {
             minE = 18432 / 2; /*Q14*/
             move16();
@@ -599,16 +611,21 @@ static void spectrum_mod_dct_fx(
 
                     Ltmp = L_mult( tmpN, m_binE ); /*2*Qdct+e_binE+9*/
                     e_binE = sub( add( e_tmp, e_binE ), 15 );
-#ifdef ISSUE_1799_replace_L_shr_o
-                    Ltmp = L_shr_sat( Ltmp, e_binE ); /*2*Qdct+9*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+                    Ltmp = L_shr_sat( Ltmp, e_binE ); /*2*Qdct+9*/                                  //??sat
+                    Lgain = L_add_sat( Ltmp, Lshift ); /*Saturation can occure here result in Q30*/ //??sat
 #else
-                    Ltmp = L_shr_o( Ltmp, e_binE, &Overflow ); /*2*Qdct+9*/
-#endif
+                    Ltmp = L_shr_o( Ltmp, e_binE, &Overflow );  /*2*Qdct+9*/
                     Lgain = L_add_o( Ltmp, Lshift, &Overflow ); /*Saturation can occure here result in Q30*/
+#endif
                 }
 
                 Lpt2++;
-                gain = round_fx_o( Lgain, &Overflow ); /*gain in Q30-16 = Q14*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+                gain = round_fx_sat( Lgain ); /*gain in Q30-16 = Q14*/ //??sat
+#else
+                gain = round_fx_o( Lgain, &Overflow );          /*gain in Q30-16 = Q14*/
+#endif
                 /*if (gain < minE)gain = minE;*/
                 gain = s_max( gain, minE ); /*Q14*/
                 /*if (gain > 1.0f+MAX_GN)gain = 1.0f+MAX_GN;*/
@@ -905,7 +922,7 @@ static Word16 norm_lfe(
 {
     Word32 Ltmp;
     Word16 exp2, tmp16, exp3;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
 #endif
@@ -929,10 +946,10 @@ static Word16 norm_lfe(
         exp3 = sub( exp2, 12 + 16 - 3 ); /* if exp2 < 31, means that tmp >= 1.0 */
         /* Need to shl by 3 to take into account the 3 multiplications */
     }
-#ifdef ISSUE_1796_replace_shl_o
-    tmp16 = shl_sat( tmp16, exp3 ); /* Result in Q12 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp16 = shl_sat( tmp16, exp3 ); /* Result in Q12 */ //??sat
 #else
-    tmp16 = shl_o( tmp16, exp3, &Overflow );                   /* Result in Q12 */
+    tmp16 = shl_o( tmp16, exp3, &Overflow );                    /* Result in Q12 */
 #endif
 
     return tmp16;
diff --git a/lib_dec/acelp_core_switch_dec_fx.c b/lib_dec/acelp_core_switch_dec_fx.c
index d166e433bce2bc2e1133fac3689acd16768aa11c..c422d63e94147c7dc8f42c7aec1b3016e4e7c9c6 100644
--- a/lib_dec/acelp_core_switch_dec_fx.c
+++ b/lib_dec/acelp_core_switch_dec_fx.c
@@ -876,7 +876,7 @@ static void decod_gen_voic_core_switch_fx(
     Word16 *pt1;
     GSC_DEC_HANDLE hGSCDec;
     hGSCDec = st_fx->hGSCDec;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
@@ -972,8 +972,8 @@ static void decod_gen_voic_core_switch_fx(
     IF( st_fx->prev_bfi )
     {
         /*gain_code = min(gain_code, 0.5f*gain_code+0.5f*st->lp_gainc);*/
-#ifdef ISSUE_1796_replace_shl_o
-        gain_code16 = s_min( gain_code16, mac_r( L_mult( 16384, gain_code16 ), shl_sat( 16384 >> 3, st_fx->Q_exc ), st_fx->lp_gainc_fx ) ); /* st_fx->lp_gainc_fx in Q3 >>3 to bring it to Q0 as gain_code16 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        gain_code16 = s_min( gain_code16, mac_r( L_mult( 16384, gain_code16 ), shl_sat( 16384 >> 3, st_fx->Q_exc ), st_fx->lp_gainc_fx ) ); /* st_fx->lp_gainc_fx in Q3 >>3 to bring it to Q0 as gain_code16 */ //??sat
 #else
         gain_code16 = s_min( gain_code16, mac_r( L_mult( 16384, gain_code16 ), shl_o( 16384 >> 3, st_fx->Q_exc, &Overflow ), st_fx->lp_gainc_fx ) ); /* st_fx->lp_gainc_fx in Q3 >>3 to bring it to Q0 as gain_code16 */
 #endif
diff --git a/lib_dec/cng_dec_fx.c b/lib_dec/cng_dec_fx.c
index fdb6488db8232ce7f77edebb2a5ea5fbb61a84b6..9de2030173509eb541de4114c37a870746881399 100644
--- a/lib_dec/cng_dec_fx.c
+++ b/lib_dec/cng_dec_fx.c
@@ -74,9 +74,11 @@ void CNG_dec_fx(
     Word16 enr_new, Aq_tmp[M + 1];
     Word16 LSF_Q_prediction; /* o  : LSF prediction mode - just temporary variable in CNG                */
     TD_CNG_DEC_HANDLE hTdCngDec;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     hTdCngDec = st_fx->hTdCngDec;
 
@@ -522,7 +524,11 @@ void CNG_dec_fx(
             FOR( i = 0; i < M; i++ )
             {
                 dev = abs_s( sub( lsp_tmp[i], lsp_new[i] ) ); /*Q15*/
-                dist = add_o( dist, dev, &Overflow );         /*Q15*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+                dist = add_sat( dist, dev ); /*Q15*/
+#else
+                dist = add_o( dist, dev, &Overflow ); /*Q15*/
+#endif
                 if ( GT_16( dev, max_dev ) )
                 {
                     max_dev = dev;
diff --git a/lib_dec/core_switching_dec_fx.c b/lib_dec/core_switching_dec_fx.c
index 106cb0e607d8e70d73cb89197d08eef43658344c..7fd3001c0ae4db21ab6497816d24023880e5e519 100644
--- a/lib_dec/core_switching_dec_fx.c
+++ b/lib_dec/core_switching_dec_fx.c
@@ -181,9 +181,11 @@ void bw_switching_pre_proc_fx(
     Word16 i;
     Word16 syn_dct_fx[L_FRAME];
     Word32 L_tmp;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
 
     IF( st_fx->element_mode > EVS_MONO )
@@ -198,7 +200,11 @@ void bw_switching_pre_proc_fx(
          * Calculate tilt of the ACELP core synthesis
          *----------------------------------------------------------------------*/
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+        st_fx->tilt_wb_fx = round_fx_sat( L_shl_sat( calc_tilt_bwe_fx( old_syn_12k8_16k_fx, -1, st_fx->L_frame ), 3 ) ); /* Q11 */ //??sat //??sat
+#else
         st_fx->tilt_wb_fx = round_fx_o( L_shl_o( calc_tilt_bwe_fx( old_syn_12k8_16k_fx, -1, st_fx->L_frame ), 3, &Overflow ), &Overflow ); /* Q11 */
+#endif
         move16();
         /*-------------------------------------------------------------------------------*
          * Calculate frequency energy of 0~3.2kHz and 3.2~6.4kHz the ACELP core synthesis
@@ -209,7 +215,11 @@ void bw_switching_pre_proc_fx(
         L_tmp = L_deposit_l( 0 );
         FOR( i = 0; i < L_FRAME / 2; i++ )
         {
-            L_tmp = L_mac0_o( L_tmp, syn_dct_fx[i], syn_dct_fx[i], &Overflow ); /* (2 * Q_syn2) */
+#ifdef ISSUE_1866_replace_overflow_libdec
+            L_tmp = L_mac0_sat( L_tmp, syn_dct_fx[i], syn_dct_fx[i] ); /* (2 * Q_syn2) */ //??sat
+#else
+            L_tmp = L_mac0_o( L_tmp, syn_dct_fx[i], syn_dct_fx[i], &Overflow );                                                            /* (2 * Q_syn2) */
+#endif
         }
         L_tmp = L_shr( L_tmp, 7 );                                              /* 2 * Q_syn2 */
         st_fx->enerLL_fx = Calc_freq_ener_fx( L_tmp, shl( st_fx->Q_syn2, 1 ) ); /* Q_syn2 */
@@ -217,7 +227,11 @@ void bw_switching_pre_proc_fx(
         L_tmp = L_deposit_l( 0 );
         FOR( ; i < L_FRAME; i++ )
         {
+#ifdef ISSUE_1866_replace_overflow_libdec
+            L_tmp = L_mac0_sat( L_tmp, syn_dct_fx[i], syn_dct_fx[i] ); //??sat
+#else
             L_tmp = L_mac0_o( L_tmp, syn_dct_fx[i], syn_dct_fx[i], &Overflow );
+#endif
         }
         L_tmp = L_shr( L_tmp, 7 );                                              /* 2 * Q_syn2 */
         st_fx->enerLH_fx = Calc_freq_ener_fx( L_tmp, shl( st_fx->Q_syn2, 1 ) ); /* Q_syn2 */
@@ -230,7 +244,11 @@ void bw_switching_pre_proc_fx(
             L_tmp = L_deposit_l( 0 );
             FOR( i = 0; i < 32; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i] ); /* 2 * Q_syn2 */ //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i], &Overflow ); /* 2 * Q_syn2 */
+#endif
             }
             L_tmp = L_shr( L_tmp, 5 );                                              /* 2 * Q_syn2 */
             st_fx->enerLL_fx = Calc_freq_ener_fx( L_tmp, shl( st_fx->Q_syn2, 1 ) ); /* Q_syn2 */
@@ -238,7 +256,11 @@ void bw_switching_pre_proc_fx(
             L_tmp = L_deposit_l( 0 );
             FOR( ; i < 64; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i] ); /* 2 * Q_syn2 */ //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i], &Overflow ); /* 2 * Q_syn2 */
+#endif
             }
             L_tmp = L_shr( L_tmp, 5 );                                              /* 2 * Q_syn2 */
             st_fx->enerLH_fx = Calc_freq_ener_fx( L_tmp, shl( st_fx->Q_syn2, 1 ) ); /* Q_syn2 */
@@ -249,7 +271,11 @@ void bw_switching_pre_proc_fx(
             L_tmp = L_deposit_l( 0 );
             FOR( i = 0; i < L_FRAME / 2; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i] ); /* 2 * Q_syn2 */ //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i], &Overflow ); /* 2 * Q_syn2 */
+#endif
             }
             L_tmp = L_shr( L_tmp, 7 );                                              /* 2 * Q_syn2 */
             st_fx->enerLL_fx = Calc_freq_ener_fx( L_tmp, shl( st_fx->Q_syn2, 1 ) ); /* Q_syn2 */
@@ -257,7 +283,11 @@ void bw_switching_pre_proc_fx(
             L_tmp = L_deposit_l( 0 );
             FOR( ; i < L_FRAME; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i] ); /* 2 * Q_syn2 */ //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st_fx->t_audio_q_fx[i], st_fx->t_audio_q_fx[i], &Overflow ); /* 2 * Q_syn2 */
+#endif
             }
             L_tmp = L_shr( L_tmp, 7 );                                              /* 2 * Q_syn2 */
             st_fx->enerLH_fx = Calc_freq_ener_fx( L_tmp, shl( st_fx->Q_syn2, 1 ) ); /* Q_syn2 */
@@ -2980,9 +3010,10 @@ void ivas_bw_switching_pre_proc_fx(
     Word16 i;
     Word32 syn_dct_fx[L_FRAME];
 
-
+#ifndef ISSUE_1866_replace_overflow_libdec
     Flag Overflow = 0;
     move32();
+#endif
 
     IF( st->element_mode > EVS_MONO )
     {
@@ -3065,7 +3096,11 @@ void ivas_bw_switching_pre_proc_fx(
             move32();
             FOR( i = 0; i < 32; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i] ); //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i], &Overflow );
+#endif
             }
             tmp = L_shr( L_tmp, 5 ); // divide by 32
             tmp = getSqrtWord32( tmp );
@@ -3078,7 +3113,11 @@ void ivas_bw_switching_pre_proc_fx(
             move32();
             FOR( ; i < 64; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i] ); //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i], &Overflow );
+#endif
             }
 
             tmp = L_shr( L_tmp, 5 ); // divide by 32
@@ -3094,7 +3133,11 @@ void ivas_bw_switching_pre_proc_fx(
             move32();
             FOR( i = 0; i < L_FRAME / 2; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i] ); //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i], &Overflow );
+#endif
             }
             tmp = L_shr( L_tmp, 5 ); // divide by 32
             tmp = getSqrtWord32( tmp );
@@ -3107,7 +3150,11 @@ void ivas_bw_switching_pre_proc_fx(
             move32();
             FOR( ; i < L_FRAME; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mac0_sat( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i] ); //??sat
+#else
                 L_tmp = L_mac0_o( L_tmp, st->t_audio_q_fx[i], st->t_audio_q_fx[i], &Overflow );
+#endif
             }
             tmp = L_shr( L_tmp, 5 ); // divide by 32
             tmp = getSqrtWord32( tmp );
diff --git a/lib_dec/dec_higher_acelp_fx.c b/lib_dec/dec_higher_acelp_fx.c
index bc638b1a13e6c264bb17bb2eeb6fa32a74ad7a40..f8d2c5ec074d09713e0816093014f176d221a0ef 100644
--- a/lib_dec/dec_higher_acelp_fx.c
+++ b/lib_dec/dec_higher_acelp_fx.c
@@ -30,7 +30,7 @@ void transf_cdbk_dec_fx(
     Word32 L_tmp;
     Word32 dct_code32[L_SUBFR];
     Word16 qdct;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -144,8 +144,8 @@ void transf_cdbk_dec_fx(
     }
     FOR( i = 0; i < L_SUBFR; i++ )
     {
-#ifdef ISSUE_1796_replace_shl_o
-        code_preQ[i] = shl_sat( code_preQ[i], q_Code_preQ );
+#ifdef ISSUE_1866_replace_overflow_libdec
+        code_preQ[i] = shl_sat( code_preQ[i], q_Code_preQ ); //??sat
 #else
         code_preQ[i] = shl_o( code_preQ[i], q_Code_preQ, &Overflow );
 #endif
diff --git a/lib_dec/dec_pit_exc_fx.c b/lib_dec/dec_pit_exc_fx.c
index e82394fbbca1343d2f561f6f14b2ac09d1e11c21..1f6e837d182ace0db67ba5d7722f0c274e6c7286 100644
--- a/lib_dec/dec_pit_exc_fx.c
+++ b/lib_dec/dec_pit_exc_fx.c
@@ -73,7 +73,7 @@ void dec_pit_exc_fx(
     Word16 use_fcb;
     Word32 gc_mem[NB_SUBFR - 1]; /* gain_code from previous subframes                    */
     Word16 gp_mem[NB_SUBFR - 1]; /* gain_pitch from previous subframes                   */
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -250,10 +250,10 @@ void dec_pit_exc_fx(
                 gain_pit_fx = st_fx->lp_gainp_fx;
                 move16();
             }
-#ifdef ISSUE_1796_replace_shl_o
-            gain_code_fx = L_mult0( s_max( sub( 32767, shl_sat( gain_pit_fx, 1 ) ), 16384 /*0.5.Q15*/ ), st_fx->lp_gainc_fx ); /* Use gain pitch and past gain code as an indicator to help finding the best scaling value. gain_code_fx used a temp var*/
-#else
+#ifndef ISSUE_1866_replace_overflow_libdec
             gain_code_fx = L_mult0( s_max( sub( 32767, shl_o( gain_pit_fx, 1, &Overflow ) ), 16384 /*0.5.Q15*/ ), st_fx->lp_gainc_fx ); /* Use gain pitch and past gain code as an indicator to help finding the best scaling value. gain_code_fx used a temp var*/
+#else
+            gain_code_fx = L_mult0( s_max( sub( 32767, shl_sat( gain_pit_fx, 1 ) ), 16384 /*0.5.Q15*/ ), st_fx->lp_gainc_fx ); /* Use gain pitch and past gain code as an indicator to help finding the best scaling value. gain_code_fx used a temp var*/ //??sat
 #endif
         }
 
diff --git a/lib_dec/dec_post_fx.c b/lib_dec/dec_post_fx.c
index f11f851cbb6eb333caabc2d00fa28b3ddf127001..d2130cddcb1ba10e52d3a5fdbd2f751966f416ad 100644
--- a/lib_dec/dec_post_fx.c
+++ b/lib_dec/dec_post_fx.c
@@ -493,19 +493,21 @@ static void modify_pst_param_fx(
     Word16 tmp;
     Word16 lp_noiseQ12;
     Word32 L_tmp;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
+#ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
 #endif
+#endif
 
 
     test();
     IF( NE_16( coder_type, INACTIVE ) && LT_16( lp_noise, LP_NOISE_THR_FX ) )
     {
-#ifdef ISSUE_1796_replace_shl_o
-        lp_noiseQ12 = shl_sat( lp_noise, 4 ); /* to go from Q8 to Q12 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        lp_noiseQ12 = shl_sat( lp_noise, 4 ); /* to go from Q8 to Q12 */ //??sat
 #else
-        lp_noiseQ12 = shl_o( lp_noise, 4, &Overflow ); /* to go from Q8 to Q12 */
+        lp_noiseQ12 = shl_o( lp_noise, 4, &Overflow );                                                                /* to go from Q8 to Q12 */
 #endif
 
         /* ftmp = lp_noise*BG1_FX + CG1_FX */
@@ -577,10 +579,12 @@ static void pst_ltp_fx(
     Word16 gain_plt;
     Word16 off_yup;
     Word16 nb_sh_sig;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
 #endif
+#endif
 
 
     /* i  signal justified on 13 bits */
@@ -679,7 +683,11 @@ static void pst_ltp_fx(
         /* decrease gain in noisy condition */
         /* gain_plt += (1.0f-gain_plt) * gain_factor */
         /* gain_plt = gain_plt + gain_factor - gain_plt*gain_factor */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        gain_plt = msu_r_sat( L_msu( L_deposit_h( gain_plt ), gain_plt, gain_factor ), -32768, gain_factor ); // Q15  //??sat
+#else
         gain_plt = msu_ro( L_msu( L_deposit_h( gain_plt ), gain_plt, gain_factor ), -32768, gain_factor, &Overflow ); // Q15
+#endif
 
         /** filtering by H0(z) = harmonic filter **/
         filt_plt_fx( ptr_sig_in, ptr_y_up, ptr_sig_pst0, gain_plt );
@@ -1423,10 +1431,12 @@ void Filt_mu_fx(
     Word16 n;
     Word16 mu, mu2, ga, temp;
     Word16 fact, sh_fact;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
 #endif
+#endif
 
 
     IF( parcor0 > 0 )
@@ -1452,7 +1462,11 @@ void Filt_mu_fx(
 
     temp = sub( 1, abs_s( mu ) );
     BASOP_SATURATE_WARNING_OFF_EVS;
-    mu2 = add_o( 32767, temp, &Overflow ); /* Q15 (1 - |mu|) */
+#ifdef ISSUE_1866_replace_overflow_libdec
+    mu2 = add_sat( 32767, temp ); /* Q15 (1 - |mu|) */ //??sat
+#else
+    mu2 = add_o( 32767, temp, &Overflow );                                                                            /* Q15 (1 - |mu|) */
+#endif
     BASOP_SATURATE_WARNING_ON_EVS;
     ga = div_s( fact, mu2 ); /* Q(sh_fact) / (1 - |mu|) */
 
@@ -1492,9 +1506,11 @@ void Filt_mu_ivas_fx(
     Word16 n;
     Word16 mu, mu2, ga, temp;
     Word16 fact, sh_fact;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
+#endif
 #endif
 
     IF( EQ_16( extl, SWB_TBE ) )
@@ -1546,7 +1562,11 @@ void Filt_mu_ivas_fx(
 
     temp = sub( 1, abs_s( mu ) );
     BASOP_SATURATE_WARNING_OFF_EVS;
-    mu2 = add_o( 32767, temp, &Overflow ); /* Q15 (1 - |mu|) */
+#ifdef ISSUE_1866_replace_overflow_libdec
+    mu2 = add_sat( 32767, temp ); /* Q15 (1 - |mu|) */ //??sat
+#else
+    mu2 = add_o( 32767, temp, &Overflow );                                                                            /* Q15 (1 - |mu|) */
+#endif
     BASOP_SATURATE_WARNING_ON_EVS;
     ga = div_s( fact, mu2 ); /* Q(sh_fact) / (1 - |mu|) */
 
@@ -1688,18 +1708,26 @@ void blend_subfr2_fx(
     Word16 fac2 = 0 + 512;     // 0.Q15 + ( 1.Q15 / L_SUBFR );
     Word16 step = 1024;        // 1.Q15 / ( L_SUBFR / 2 );
     Word16 i;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
+#endif
 #endif
     move16();
     move16();
     move16();
     FOR( i = 0; i < L_SUBFR / 2; i++ )
     {
-        sigOut[i] = mac_ro( L_mult_o( fac1, sigIn1[i], &Overflow ), fac2, sigIn2[i], &Overflow ); // Qx
+#ifdef ISSUE_1866_replace_overflow_libdec
+        sigOut[i] = mac_r_sat( L_mult( fac1, sigIn1[i] ), fac2, sigIn2[i] ); // Qx  //??sat
+        fac1 = sub_sat( fac1, step );                                        //??sat
+        fac2 = add_sat( fac2, step );                                        //??sat
+#else
+        sigOut[i] = mac_ro( L_mult_o( fac1, sigIn1[i], &Overflow ), fac2, sigIn2[i], &Overflow );                     // Qx
         fac1 = sub_o( fac1, step, &Overflow );
         fac2 = add_o( fac2, step, &Overflow );
+#endif
         move16();
     }
 
diff --git a/lib_dec/dec_tcx_fx.c b/lib_dec/dec_tcx_fx.c
index d1d290b86f8fd35af06008949990ac1a6b9f90f9..664b22e938163788af28a4c37e268e5bae21c435 100644
--- a/lib_dec/dec_tcx_fx.c
+++ b/lib_dec/dec_tcx_fx.c
@@ -547,7 +547,11 @@ void decoder_tcx_fx(
             st->last_gain_syn_deemph_e = add( st->last_gain_syn_deemph_e, 10 /*scaling of h1[0] and E_UTIL_synthesis * 2*/ );
             move16();
             tmp32 = Sqrt32( tmp32, &st->last_gain_syn_deemph_e );
+#ifdef ISSUE_1866_replace_overflow_libdec
+            st->last_gain_syn_deemph = round_fx_sat( tmp32 ); //??sat
+#else
             st->last_gain_syn_deemph = round_fx_o( tmp32, &Overflow );
+#endif
             move16();
             /*for avoiding compiler warnings*/
             hTcxDec->gainHelper = 32768 / 2;
@@ -1276,9 +1280,11 @@ void decoder_tcx_post_fx( Decoder_State *st_fx,
     Word32 tmp32;
     Word32 tmp32_1, tmp32_2;
     TCX_DEC_HANDLE hTcxDec;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
 
     hTcxDec = st_fx->hTcxDec;
@@ -1351,7 +1357,11 @@ void decoder_tcx_post_fx( Decoder_State *st_fx,
     }
     tmp32 = Mpy_32_16_1( tmp32, getInvFrameLen( hTcxDec->L_frameTCX ) );
     tmp2 = norm_l( tmp32 );
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp1 = round_fx_sat( L_shl( tmp32, tmp2 ) ); //??sat
+#else
     tmp1 = round_fx_o( L_shl( tmp32, tmp2 ), &Overflow );
+#endif
     s = sub( sub( sub( 1, shl( s, 1 ) ), 6 /*table lookup for inverse framelength*/ ), tmp2 );
     tmp1 = Sqrt16( tmp1, &s );
     move16();
@@ -1444,18 +1454,30 @@ void decoder_tcx_post_fx( Decoder_State *st_fx,
             &tmp1 );
         tmp2 = BASOP_Util_Add_MantExp( hTcxDec->conceal_eof_gain, 15 - 14, negate( tmp1 ), tmp2, &tmp1 );
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+        step = L_shl_sat( L_mult( tmp1, getInvFrameLen( st_fx->L_frame ) ), sub( tmp2, 6 /*scaling from table lookup*/ + 1 /*go to Q30*/ ) ); /*Q30*/ //??sat
+#else
         step = L_shl_o( L_mult( tmp1, getInvFrameLen( st_fx->L_frame ) ), sub( tmp2, 6 /*scaling from table lookup*/ + 1 /*go to Q30*/ ), &Overflow ); /*Q30*/
+#endif
         {
             Word32 stepFB;
             UWord32 dmy;
             conceal_eof_gainFB = L_deposit_h( hTcxDec->conceal_eof_gain ); /*Q30*/
             Mpy_32_32_ss( step, L_shl( L_mult0( st_fx->L_frame, getInvFrameLen( hTcxDec->L_frameTCX ) ), 8 ), &stepFB, &dmy );
-            stepFB = L_shl_o( stepFB, 3 - 1, &Overflow ); /*Q30*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+            stepFB = L_shl_sat( stepFB, 3 - 1 ); /*Q30*/ //??sat
+#else
+            stepFB = L_shl_o( stepFB, 3 - 1, &Overflow );                                                                                              /*Q30*/
+#endif
             FOR( i = 0; i < hTcxDec->L_frameTCX; i++ )
             {
                 synthFB[i] = round_fx_sat( L_shl_sat( Mpy_32_16_1( conceal_eof_gainFB, synthFB[i] ), 1 ) );
                 move16();
+#ifdef ISSUE_1866_replace_overflow_libdec
+                conceal_eof_gainFB = L_sub_sat( conceal_eof_gainFB, stepFB ); //??sat
+#else
                 conceal_eof_gainFB = L_sub_o( conceal_eof_gainFB, stepFB, &Overflow );
+#endif
             }
         }
         conceal_eof_gain32 = L_deposit_h( hTcxDec->conceal_eof_gain ); /*Q30*/
@@ -1463,17 +1485,32 @@ void decoder_tcx_post_fx( Decoder_State *st_fx,
         {
             xn_buf[i] = round_fx_sat( L_shl_sat( Mpy_32_16_1( conceal_eof_gain32 /*Q30*/, xn_buf[i] ), 1 ) );
             move16();
+#ifdef ISSUE_1866_replace_overflow_libdec
+            conceal_eof_gain32 = L_sub_sat( conceal_eof_gain32, step ); //??sat
+#else
             conceal_eof_gain32 = L_sub_o( conceal_eof_gain32, step, &Overflow );
+#endif
         }
+#ifdef ISSUE_1866_replace_overflow_libdec
+        hTcxDec->conceal_eof_gain = round_fx_sat( conceal_eof_gain32 ); /*Q14*/ //??sat
+#else
         hTcxDec->conceal_eof_gain = round_fx_o( conceal_eof_gain32, &Overflow ); /*Q14*/
+#endif
         move16();
         /* run lpc gain compensation not for waveform adjustment */
         test();
         IF( 0 == st_fx->enablePlcWaveadjust || EQ_16( st_fx->hPlcInfo->concealment_method, TCX_TONAL ) )
         {
+#ifdef ISSUE_1866_replace_overflow_libdec
+            st_fx->hPlcInfo->recovery_gain = extract_h( L_shl_sat( Mpy_32_16_1( conceal_eof_gainFB,
+                                                                                st_fx->last_concealed_gain_syn_deemph ),
+                                                                   st_fx->last_concealed_gain_syn_deemph_e ) );
+            /*Q30->Q14*/ //??sat
+#else
             st_fx->hPlcInfo->recovery_gain = extract_h( L_shl_o( Mpy_32_16_1( conceal_eof_gainFB,
                                                                               st_fx->last_concealed_gain_syn_deemph ),
                                                                  st_fx->last_concealed_gain_syn_deemph_e, &Overflow ) ); /*Q30->Q14*/
+#endif
             move16();
         }
         ELSE
@@ -1543,9 +1580,11 @@ void decoder_tcx_post_ivas_fx( Decoder_State *st_fx,
     Word32 tmp32;
     Word32 tmp32_1, tmp32_2;
     TCX_DEC_HANDLE hTcxDec;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
 
     hTcxDec = st_fx->hTcxDec;
@@ -1629,7 +1668,11 @@ void decoder_tcx_post_ivas_fx( Decoder_State *st_fx,
     }
     tmp32 = Mpy_32_16_1( tmp32, getInvFrameLen( hTcxDec->L_frameTCX ) );
     tmp2 = norm_l( tmp32 );
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp1 = round_fx_sat( L_shl( tmp32, tmp2 ) ); //??sat
+#else
     tmp1 = round_fx_o( L_shl( tmp32, tmp2 ), &Overflow );
+#endif
     // s = sub(sub(sub(1, shl(s, 1)), 6/*table lookup for inverse framelength*/), tmp2);
     s = sub( 25, add( shl( add( Q_syn, s ), 1 ), tmp2 ) );
     tmp1 = Sqrt16( tmp1, &s );
@@ -1802,7 +1845,11 @@ void decoder_tcx_post_ivas_fx( Decoder_State *st_fx,
             test();
             IF( 0 == st_fx->enablePlcWaveadjust || EQ_16( st_fx->hPlcInfo->concealment_method, TCX_TONAL ) )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                st_fx->hPlcInfo->recovery_gain = extract_h( L_shl_sat( Mpy_32_16_1( conceal_eof_gainFB, st_fx->last_concealed_gain_syn_deemph ), st_fx->last_concealed_gain_syn_deemph_e ) ); /*Q30->Q14*/ //??sat
+#else
                 st_fx->hPlcInfo->recovery_gain = extract_h( L_shl_o( Mpy_32_16_1( conceal_eof_gainFB, st_fx->last_concealed_gain_syn_deemph ), st_fx->last_concealed_gain_syn_deemph_e, &Overflow ) ); /*Q30->Q14*/
+#endif
                 move16();
             }
             ELSE
@@ -4410,9 +4457,11 @@ void decoder_tcx_invQ_fx(
     move16();
     move16();
 
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
 
     tnsSize = 0;
@@ -4537,7 +4586,11 @@ void decoder_tcx_invQ_fx(
                 FOR( i = 0; i < noiseFillingSize; ++i )
                 {
                     tmp32 = L_shr( x[i], sub( 31, *x_e ) );
+#ifdef ISSUE_1866_replace_overflow_libdec
+                    *nf_seed = add_sat( *nf_seed, extract_l( L_shl( i_mult( (Word16) L_abs( tmp32 ), i ), 1 ) ) ); // abs( tmp32 ) * i * 2 //??sat
+#else
                     *nf_seed = add_o( *nf_seed, extract_l( L_shl( i_mult( (Word16) L_abs( tmp32 ), i ), 1 ) ), &Overflow ); // abs( tmp32 ) * i * 2
+#endif
                     move16();
                 }
             }
@@ -4777,7 +4830,11 @@ void decoder_tcx_invQ_fx(
             st->last_gain_syn_deemph_e = add( st->last_gain_syn_deemph_e, 10 /*scaling of h1[0] and E_UTIL_synthesis * 2*/ );
             move16();
             tmp32 = Sqrt32( tmp32, &st->last_gain_syn_deemph_e );
-            st->last_gain_syn_deemph = round_fx_o( tmp32, &Overflow ); // Q15
+#ifdef ISSUE_1866_replace_overflow_libdec
+            st->last_gain_syn_deemph = round_fx_sat( tmp32 ); // Q15   //??sat
+#else
+            st->last_gain_syn_deemph = round_fx_o( tmp32, &Overflow );                                                      // Q15
+#endif
             move16();
         }
 
diff --git a/lib_dec/er_dec_tcx_fx.c b/lib_dec/er_dec_tcx_fx.c
index aeb4c0783a0ff156761eef9263cbc451a1a354cf..9d0a3cc44912e9a3f89342a616cfc9370ac7375d 100644
--- a/lib_dec/er_dec_tcx_fx.c
+++ b/lib_dec/er_dec_tcx_fx.c
@@ -36,14 +36,22 @@ static void calcGainc_fx( Word16 *exc, Word16 Q_exc, Word32 old_fpitch /*Q16*/,
     tmp16 = round_fx( old_fpitch ); /*Q0*/
     tmp_loop = shl( L_subfr, 1 );
     BASOP_SATURATE_WARNING_OFF_EVS
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp16_2 = round_fx_sat( L_shl_sat( lp_gainp, 2 ) ); /*Q31->Q15, no severe saturation, because st->lp_gainp here is [0,1]*/ //??sat //??sat
+#else
     tmp16_2 = round_fx_o( L_shl_o( lp_gainp, 2, &Overflow ), &Overflow ); /*Q31->Q15, no severe saturation, because st->lp_gainp here is [0,1]*/
+#endif
     BASOP_SATURATE_WARNING_ON_EVS
 
     FOR( i = 0; i < tmp_loop; i++ )
     {
         /*st->lp_gainc += ( exc[i-2*L_subfr] - st->Mode2_lp_gainp * exc[i-2*L_subfr-(int)(st->old_fpitch+0.5f)] ) *
                           ( exc[i-2*L_subfr] - st->Mode2_lp_gainp * exc[i-2*L_subfr-(int)(st->old_fpitch+0.5f)] );*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+        tmp16_3 = sub_sat( exc[( i - ( L_subfr * 2 ) )] /*Q1*/, mult_r( tmp16_2 /*Q15*/, exc[( ( i - ( L_subfr * 2 ) ) - tmp16 )] /*Q1*/ ) /*Q1*/ ); //??sat
+#else
         tmp16_3 = sub_o( exc[( i - ( L_subfr * 2 ) )] /*Q1*/, mult_r( tmp16_2 /*Q15*/, exc[( ( i - ( L_subfr * 2 ) ) - tmp16 )] /*Q1*/ ) /*Q1*/, &Overflow );
+#endif
         L_acc = L_macNs_co( L_acc, tmp16_3, tmp16_3, &Carry, &Overflow ); /*Q3*/
         Overflow = 0;
         move16();
diff --git a/lib_dec/er_scale_syn_fx.c b/lib_dec/er_scale_syn_fx.c
index 35ad826486d758fbbaa190df3afa1374320fc238..195d79d9edac4c30a4f1d90f0aa870f7fb3e8ed3 100644
--- a/lib_dec/er_scale_syn_fx.c
+++ b/lib_dec/er_scale_syn_fx.c
@@ -33,10 +33,12 @@ Word16 Damping_fact_fx( /* o : damping factor
     Word32 lp_tmp;
     Word16 s_gainp;
     Word32 gain32;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
 #endif
+#endif
 
 
     IF( core == ACELP_CORE )
@@ -97,10 +99,14 @@ Word16 Damping_fact_fx( /* o : damping factor
                 move16();
                 gain32 = Sqrt32( lp_tmp, &s_gainp ); /*Q31-s_gainp*/
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+                gain = round_fx_sat( L_shl_sat( gain32, s_gainp ) ); /* Q15*/ //??sat //??sat
+#else
                 gain = round_fx_o( L_shl_o( gain32, s_gainp, &Overflow ), &Overflow ); /* Q15*/
-                gain = s_min( gain, 32113 /*0.98f Q15*/ );                             /*Q15*/
-                gain = s_max( gain, 27853 /*0.85f Q15*/ );                             /*Q15*/
-                alpha = mult_r( alpha, gain );                                         /*Q14*/
+#endif
+                gain = s_min( gain, 32113 /*0.98f Q15*/ ); /*Q15*/
+                gain = s_max( gain, 27853 /*0.85f Q15*/ ); /*Q15*/
+                alpha = mult_r( alpha, gain );             /*Q14*/
             }
             ELSE IF( EQ_16( nbLostCmpt, 2 ) )
             {
diff --git a/lib_dec/er_sync_exc_fx.c b/lib_dec/er_sync_exc_fx.c
index 48be80d43cecd12d70b57d6f2d4d8a47c93cbe3a..77a2eb294f82685a17f29c7367802a317ac4a948 100644
--- a/lib_dec/er_sync_exc_fx.c
+++ b/lib_dec/er_sync_exc_fx.c
@@ -30,9 +30,11 @@ static Word16 GetMinimumPosition_fx(
     Word16 iMinEnergyPos, center, i;
     Word16 cnt, tmp_e, tmp16;
     Word32 energy, energy_old, tmptest;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
+#endif
 #endif
 
     filterLength = s_min( filterLength, length ); /*Q0*/
@@ -60,8 +62,13 @@ static Word16 GetMinimumPosition_fx(
             BASOP_SATURATE_WARNING_ON_EVS
 
             /*if (energy == MAXVAL_WORD32)*/
-            BASOP_SATURATE_WARNING_OFF_EVS                             /*saturates if energy < 0*/
-                tmptest = L_sub_o( energy, MAXVAL_WORD32, &Overflow ); /*Q31*/
+            BASOP_SATURATE_WARNING_OFF_EVS /*saturates if energy < 0*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+                tmptest = L_sub_sat( energy, MAXVAL_WORD32 );
+            /*Q31*/ //??sat
+#else
+                tmptest = L_sub_o( energy, MAXVAL_WORD32, &Overflow );                     /*Q31*/
+#endif
             BASOP_SATURATE_WARNING_ON_EVS
             IF( tmptest == 0 )
             {
@@ -227,10 +234,12 @@ void PulseResynchronization_fx(
     Word16 /*int*/ roundedPitchStart, nSamplesDelta, nSamplesDeltaRemain, iMinPos1, iMinPos[NB_PULSES_MAX + 1], iDeltaSamples[NB_PULSES_MAX + 1], maxDeltaSamples, roundedCycleDelta;
     Word16 tmp16, tmp16_a, freqStart_e /*exponent of freqStart*/, tmp_e, samplesDelta_e, perCycleDeltaDelta_e, cycleDelta_e, tmp2_e, tmp3_e;
     Word32 /* pitchDelta, */ tmp32, tmp32_a, tmp32_b, samplesDelta, absPitchDiff, cycleDelta32;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
 #endif
+#endif
 
 
     test();
@@ -295,7 +304,11 @@ void PulseResynchronization_fx(
     tmp3_e = tmp2_e;
     move16();
     tmp32_a = L_negate( tmp32_a );
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp32_a = L_add( L_shl_sat( 1, sub( 31, tmp3_e ) ), tmp32_a ); /*Q31,tmp3_e*/ /*tmp32_a= 1.0f-pitchStart*freqStart*/ //??sat
+#else
     tmp32_a = L_add( L_shl_o( 1, sub( 31, tmp3_e ), &Overflow ), tmp32_a ); /*Q31,tmp3_e*/ /*tmp32_a= 1.0f-pitchStart*freqStart*/
+#endif
     tmp2_e = norm_s( nFrameLength );
     tmp16_a = shl( nFrameLength, tmp2_e );                                                         /*Q0+tmp2_e*/
     tmp32_a = Mpy_32_16_1( tmp32_a /*Q31,tmp3_e*/, tmp16_a /*Q0,-tmp2_e*/ ); /*Q16,tmp3_e-tmp2_e*/ /*tmp32_a= nFrameLength*(1.0f-pitchStart*freqStart)*/
@@ -360,8 +373,12 @@ void PulseResynchronization_fx(
         fractionalLeft = lshr( extract_l( tmp32_a ), 1 ); /*Q15*/
         tmp_e = sub( 15, norm_l( tmp32 ) );
         cycleDelta_e = add( cycleDelta_e, tmp_e );
-        tmp32 = L_shr( tmp32, sub( tmp_e, 15 ) );    /*Q31 frac, cycleDelta_e*/
-        cycleDelta = round_fx_o( tmp32, &Overflow ); /*Q15, cycleDelta_e*/
+        tmp32 = L_shr( tmp32, sub( tmp_e, 15 ) ); /*Q31 frac, cycleDelta_e*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+        cycleDelta = round_fx_sat( tmp32 ); /*Q15, cycleDelta_e*/ //??sat
+#else
+        cycleDelta = round_fx_o( tmp32, &Overflow );                                       /*Q15, cycleDelta_e*/
+#endif
         if ( cycleDelta == 0 )
         {
             cycleDelta_e = 0;
diff --git a/lib_dec/er_util_fx.c b/lib_dec/er_util_fx.c
index 330cb5d4452ce4f80eda4d441ca7e3f0a4a931ce..72dc9387c8e6d941e6750f4d42671f8852b439a7 100644
--- a/lib_dec/er_util_fx.c
+++ b/lib_dec/er_util_fx.c
@@ -44,7 +44,7 @@ void minimumStatistics_fx(
     Word16 f, p, i;
     Word16 tmp, tmp2, tmp_e;
     Word32 tmp32;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
@@ -55,8 +55,8 @@ void minimumStatistics_fx(
 
 
     BASOP_SATURATE_WARNING_OFF_EVS
-#ifdef ISSUE_1796_replace_shl_o
-    IF( LT_16( shl_sat( currentFrameLevel, currentFrameLevel_e ), PLC_MIN_CNG_LEV ) )
+#ifdef ISSUE_1866_replace_overflow_libdec
+    IF( LT_16( shl_sat( currentFrameLevel, currentFrameLevel_e ), PLC_MIN_CNG_LEV ) ) //??sat
 #else
     IF( LT_16( shl_o( currentFrameLevel, currentFrameLevel_e, &Overflow ), PLC_MIN_CNG_LEV ) )
 #endif
diff --git a/lib_dec/evs_dec_fx.c b/lib_dec/evs_dec_fx.c
index e411da152af54a0e1f8418a05a7759f0bb3746c7..c5f2d4708b603a8ab5f95452f613ec7fe6a70e5c 100644
--- a/lib_dec/evs_dec_fx.c
+++ b/lib_dec/evs_dec_fx.c
@@ -62,9 +62,11 @@ ivas_error evs_dec_fx(
 
     push_wmops( "evs_dec_fx" );
 
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
+#endif
 #endif
     hBWE_TD = st_fx->hBWE_TD;
     hHQ_core = st_fx->hHQ_core;
@@ -454,7 +456,11 @@ ivas_error evs_dec_fx(
                 /*hb_synth[i] *= (i*tmp);*/
                 hb_synth_fx[i] = mult_r( hb_synth_fx[i], tmp16_2 ); /*hb_synth_fx_exp*/
                 move16();
+#ifdef ISSUE_1866_replace_overflow_libdec
+                tmp16_2 = add_sat( tmp16_2, tmp16 ); //??sat
+#else
                 tmp16_2 = add_o( tmp16_2, tmp16, &Overflow );
+#endif
             }
         }
 
diff --git a/lib_dec/fd_cng_dec_fx.c b/lib_dec/fd_cng_dec_fx.c
index 1e78b792becb0373958b675bf9a4995e0e4fd819..91b566fe656d904d0221e9819d43b0c6c4ae2384 100644
--- a/lib_dec/fd_cng_dec_fx.c
+++ b/lib_dec/fd_cng_dec_fx.c
@@ -583,7 +583,9 @@ Word16 ApplyFdCng_fx(
     HANDLE_FD_CNG_DEC hFdCngDec;
     HANDLE_FD_CNG_COM hFdCngCom;
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
+#if !defined( ISSUE_1866_replace_overflow_libdec ) && !defined( FIX_ISSUE_1817_REPLACE_CARRY_OVERFLOW )
     Flag Overflow = 0;
+#endif
 #ifndef FIX_ISSUE_1817_REPLACE_CARRY_OVERFLOW
     Flag Carry = 0;
 #endif
@@ -983,7 +985,11 @@ Word16 ApplyFdCng_fx(
                 }
                 L_tmp_exp = 0;
                 move16();
+#ifdef ISSUE_1866_replace_overflow_libdec
+                IF( GT_32( L_tmp, 21474836 ) /*0.01f Q31*/ )
+#else
                 IF( GT_32( L_shl_o( L_tmp, L_tmp_exp, &Overflow ), 21474836 ) /*0.01f Q31*/ )
+#endif
                 {
                     test();
                     test();
@@ -1093,7 +1099,11 @@ Word16 ApplyFdCng_fx(
                 L_tmp_exp = add( L_tmp_exp, -7 );                                                               /*->Q16, L_tmp_exp */
                 L_tmp_exp = add( L_tmp_exp, 31 - 16 );                                                          /*->Q31, L_tmp_exp*/
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+                st->cngTDLevel = round_fx_sat( Sqrt32( L_tmp, &L_tmp_exp ) ); /*Q15 - L_tmp_exp*/ //??sat
+#else
                 st->cngTDLevel = round_fx_o( Sqrt32( L_tmp, &L_tmp_exp ), &Overflow ); /*Q15 - L_tmp_exp*/
+#endif
                 move16();
 #else
                 L_tmp = sum_array_norm( cngNoiseLevel, tmp_loop, &L_tmp_exp ); /*Q31 - L_tmp_exp*/
diff --git a/lib_dec/gain_dec_fx.c b/lib_dec/gain_dec_fx.c
index db325cd80b92a8be09722e96ce43d699613736e6..267041c3703c3053932148bd6a06d22051536ede 100644
--- a/lib_dec/gain_dec_fx.c
+++ b/lib_dec/gain_dec_fx.c
@@ -1409,10 +1409,12 @@ void gain_dec_amr_wb_fx(
     Word16 tmp;
     Word32 L_tmp;
     Word16 expg, exp_gcode0, fracg;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
 #endif
+#endif
 
 
     /**gain_inov = 1.0f/ (float)sqrt( ( dotp( code, code, L_SUBFR ) + 0.01f ) / L_SUBFR );*/
@@ -1496,7 +1498,11 @@ void gain_dec_amr_wb_fx(
 
     /* adjust gain according to energy of code */
     L_tmp = Mult_32_16( *gain_code, *gain_inov );
+#ifdef ISSUE_1866_replace_overflow_libdec
+    *gain_code = L_shl_sat( L_tmp, 3 ); /* gcode_inov in Q12*/ //??sat
+#else
     *gain_code = L_shl_o( L_tmp, 3, &Overflow ); /* gcode_inov in Q12*/
+#endif
     move32();
 
     /*-----------------------------------------------------------------*
diff --git a/lib_dec/hf_synth_fx.c b/lib_dec/hf_synth_fx.c
index 27d768f631bb7b007adeeae34f78ffe698833ad7..0bb28934412f35f7ada8abe35a6b9b78d6193010 100644
--- a/lib_dec/hf_synth_fx.c
+++ b/lib_dec/hf_synth_fx.c
@@ -136,9 +136,11 @@ static void hf_synthesis_fx(
     Word16 tmp, ener, exp1, exp2, scale;
     Word32 L_tmp;
     Word16 Ap[M16k + 1];
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
 
     /*-----------------------------------------------------------------*
@@ -217,15 +219,22 @@ static void hf_synthesis_fx(
     /*-----------------------------------------------------------------*
      * modify energy of white noise according to synthesis tilt
      *-----------------------------------------------------------------*/
-
     /* tmp = 1.0 - fac */
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp = add_sat( 1, sub( 32767 /* 1 in Q15 */, tmp ) ); //??sat
+#else
     tmp = add_o( 1, sub( 32767 /* 1 in Q15 */, tmp ), &Overflow );
+#endif
     test();
     if ( core_brate == FRAME_NO_DATA || EQ_32( core_brate, SID_2k40 ) )
     {
         /* emphasize HF noise in CNG */
         /*fac *= 2.0f;*/
-        tmp = add_o( tmp, tmp, &Overflow ); /* Q15 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        tmp = add_sat( tmp, tmp ); /* Q15 */ //??sat
+#else
+        tmp = add_o( tmp, tmp, &Overflow );                                 /* Q15 */
+#endif
     }
     tmp = s_max( tmp, 3277 ); /* 0.1 in Q15 */
 
@@ -523,9 +532,11 @@ static void filt_6k_7k_scale_fx(
 {
     Word16 i, x[L_FRAME48k / NB_SUBFR + ( L_FIR - 1 )];
     Word32 L_tmp;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     Copy_Scale_sig( mem, x, L_FIR - 1, exp );
 
@@ -542,10 +553,18 @@ static void filt_6k_7k_scale_fx(
         move32();
         FOR( j = 0; j < 31; j++ )
         {
+#ifdef ISSUE_1866_replace_overflow_libdec
+            L_tmp = L_mac_sat( L_tmp, x[i + j], fir_6k_7k_fx[j] ); /* Q16 */ //??sat
+#else
             L_tmp = L_mac_o( L_tmp, x[i + j], fir_6k_7k_fx[j], &Overflow ); /* Q16 */
+#endif
         }
 
-        signal[i] = round_fx_o( L_tmp, &Overflow ); /* Q0 */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        signal[i] = round_fx_sat( L_tmp ); /* Q0 */ //??sat
+#else
+        signal[i] = round_fx_o( L_tmp, &Overflow );                         /* Q0 */
+#endif
         move16();
     }
     Copy( x + lg, mem, L_FIR - 1 ); /* Qx - 2 */
@@ -1385,8 +1404,9 @@ static Word16 EnhanceClass_fx(
     Word16 unvoicing_tmp_fx;
     Word16 tmp, tmp1;
     Word32 L_tmp;
+#ifndef ISSUE_1866_replace_overflow_libdec
     Flag Overflow;
-
+#endif
 
     /* Decide (*unvoicing_flag) to allow BWE enhancement when qq>pp */
     /**voice_fac_fx = add(mult_r(*voice_fac_fx, 24576), mult_r(voice_factor_fx, 8192));  //Q15 */
@@ -1423,13 +1443,21 @@ static Word16 EnhanceClass_fx(
         move16();
     }
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+    if ( GT_16( sub_sat( *unvoicing_fx, *unvoicing_sm_fx ), 3277 /* 0.1 in Q15 */ ) ) //??sat
+#else
     if ( GT_16( sub_o( *unvoicing_fx, *unvoicing_sm_fx, &Overflow ), 3277 /* 0.1 in Q15 */ ) )
+#endif
     {
         *unvoicing_flag = 1;
         move16();
     }
 
+#ifdef ISSUE_1866_replace_overflow_libdec
+    if ( LT_16( sub_sat( *unvoicing_fx, *unvoicing_sm_fx ), 1638 /* 0.05 in Q15 */ ) ) //??sat
+#else
     if ( LT_16( sub_o( *unvoicing_fx, *unvoicing_sm_fx, &Overflow ), 1638 /* 0.05 in Q15 */ ) )
+#endif
     {
         *unvoicing_flag = 0;
         move16();
diff --git a/lib_dec/igf_dec_fx.c b/lib_dec/igf_dec_fx.c
index 40b02c82315c383281a2b69656305999573e1ab0..3ae2927e82ba5fb0a5d345c95ec78c920aa849a0 100644
--- a/lib_dec/igf_dec_fx.c
+++ b/lib_dec/igf_dec_fx.c
@@ -1884,8 +1884,12 @@ static void IGF_appl( IGF_DEC_PRIVATE_DATA_HANDLE hPrivateData,          /**< in
         sum = shl( sum, shift ); /* exponent of sum: sub(15, shift) */
 
         /* divide E by sum */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        tmp = div_s( shr( round_fx_sat( E ), 1 ), sum ); /* shift E 1 bit to the right in order to make it smaller than sum */ //??sat
+#else
         tmp = div_s( shr( round_fx_o( E, &Overflow ), 1 ), sum ); /* shift E 1 bit to the right in order to make it smaller than sum */
-        tmp_e = sub( add( E_e, 1 ), sub( 15, shift ) );           /* 15Q0 | sum is 15Q0 */
+#endif
+        tmp_e = sub( add( E_e, 1 ), sub( 15, shift ) ); /* 15Q0 | sum is 15Q0 */
 
         /* multiply the result by the hopsize */
         L_tmp = L_mult( tmp, hopsize );
@@ -2571,8 +2575,12 @@ static void IGF_appl_ivas( IGF_DEC_PRIVATE_DATA_HANDLE hPrivateData,     /**< in
         sum = shl( sum, shift ); /* exponent of sum: sub(15, shift) */
 
         /* divide E by sum */
+#ifdef ISSUE_1866_replace_overflow_libdec
+        tmp = div_s( shr( round_fx_sat( E ), 1 ), sum ); /* shift E 1 bit to the right in order to make it smaller than sum */ //??sat
+#else
         tmp = div_s( shr( round_fx_o( E, &Overflow ), 1 ), sum ); /* shift E 1 bit to the right in order to make it smaller than sum */
-        tmp_e = sub( add( E_e, 1 ), sub( 15, shift ) );           /* 15Q0 | sum is 15Q0 */
+#endif
+        tmp_e = sub( add( E_e, 1 ), sub( 15, shift ) ); /* 15Q0 | sum is 15Q0 */
 
         /* multiply the result by the hopsize */
         L_tmp = L_mult( tmp, hopsize );
@@ -2975,7 +2983,7 @@ static void IGF_RefineGrid( H_IGF_GRID hGrid                             /**< in
     Word16 sfb;
     Word16 tmp;
     Word16 delta;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
@@ -2994,8 +3002,8 @@ static void IGF_RefineGrid( H_IGF_GRID hGrid                             /**< in
         move16();
         tmp = add( tmp, 1 );
         delta = sub( hGrid->swb_offset[sfb + 1], hGrid->swb_offset[sfb] );
-#ifdef ISSUE_1796_replace_shl_o
-        delta = mac_r( 0x00195000, 29491 /*0.45f Q16*/, shl_sat( delta, 5 ) );
+#ifdef ISSUE_1866_replace_overflow_libdec
+        delta = mac_r( 0x00195000, 29491 /*0.45f Q16*/, shl_sat( delta, 5 ) ); //??sat
 #else
         delta = mac_r( 0x00195000, 29491 /*0.45f Q16*/, shl_o( delta, 5, &Overflow ) );
 #endif
@@ -3029,7 +3037,7 @@ static void IGF_RefineGrid_ivas_fx( H_IGF_GRID hGrid /**< in/out: | IGF grid han
     Word16 sfb;
     Word16 tmp;
     Word16 delta;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
@@ -3049,7 +3057,7 @@ static void IGF_RefineGrid_ivas_fx( H_IGF_GRID hGrid /**< in/out: | IGF grid han
         tmp = add( tmp, 1 );
         delta = sub( hGrid->swb_offset[sfb + 1], hGrid->swb_offset[sfb] );
 #ifdef ISSUE_1796_replace_shl_o
-        delta = mac_r( 0x00195000, 29491 /*0.45f Q16*/, shl_sat( delta, 5 ) );
+        delta = mac_r( 0x00195000, 29491 /*0.45f Q16*/, shl_sat( delta, 5 ) ); //??sat
 #else
         delta = mac_r( 0x00195000, 29491 /*0.45f Q16*/, shl_o( delta, 5, &Overflow ) );
 #endif
diff --git a/lib_dec/ivas_core_dec_fx.c b/lib_dec/ivas_core_dec_fx.c
index bc9adf34791b348a940a92b1b06f655352b2b1cd..cfdb13801c4887f7510b21d94b61d10f650000b9 100644
--- a/lib_dec/ivas_core_dec_fx.c
+++ b/lib_dec/ivas_core_dec_fx.c
@@ -116,7 +116,9 @@ ivas_error ivas_core_dec_fx(
     Word16 tdm_lsfQ_PCh_fx[M], tdm_lspQ_PCh_fx[M];
 #endif
     Word32 conceal_eof_gain32;
+#ifndef ISSUE_1866_replace_overflow_libdec
     Flag Overflow;
+#endif
 
     error = IVAS_ERR_OK;
     move32();
@@ -1141,7 +1143,11 @@ ivas_error ivas_core_dec_fx(
             {
                 hb_synth_32_fx[n][i] = Mpy_32_16_1( hb_synth_32_fx[n][i], tmp16_2 ); /* Q11 */
                 move32();
+#ifdef ISSUE_1866_replace_overflow_libdec
+                tmp16_2 = add_sat( tmp16_2, tmp16 ); /* Q15 */ //??sat
+#else
                 tmp16_2 = add_o( tmp16_2, tmp16, &Overflow ); /* Q15 */
+#endif
             }
         }
 
diff --git a/lib_dec/pitch_extr_fx.c b/lib_dec/pitch_extr_fx.c
index 73e9623f5da99fc082caae28ff4ce9c12a27bd20..4b159ee157a0e8dcb420e1ddbe51cb24dd49f5d0 100644
--- a/lib_dec/pitch_extr_fx.c
+++ b/lib_dec/pitch_extr_fx.c
@@ -157,7 +157,9 @@ void pitch_pred_linear_fit(
             {
                 Word32 t1, t2, t3, t4, t5, t6, t7;
                 Word16 e1, e2, e3, e4, e5, e6, e7;
+#ifndef ISSUE_1866_replace_overflow_libdec
                 Flag Overflow;
+#endif
                 t1 = L_mult0( pg[4], pg[3] ); /*Q24*/ /* t1 = pg[4]*pg[3] */
                 e1 = 7;
                 move16();
@@ -180,8 +182,12 @@ void pitch_pred_linear_fit(
                 t6 = BASOP_Util_Add_Mant32Exp( t3, e3, t4, e4, &e6 );
                 t7 = BASOP_Util_Add_Mant32Exp( t5, e5, t6, e6, &e7 ); /*Q31,e7*/
                 sum0_q = norm_l( t7 );
+#ifdef ISSUE_1866_replace_overflow_libdec
+                sum0 = round_fx_sat( L_shl( t7, sum0_q ) ); /*Q15,e7-sum0_q*/ //??sat
+#else
                 sum0 = round_fx_o( L_shl( t7, sum0_q ), &Overflow ); /*Q15,e7-sum0_q*/
-                sum0_q = add( 15, sub( sum0_q, e7 ) );               /* sum0 is now Qsum0_q*/
+#endif
+                sum0_q = add( 15, sub( sum0_q, e7 ) ); /* sum0 is now Qsum0_q*/
             }
 
             pit = 0;
diff --git a/lib_dec/post_dec_fx.c b/lib_dec/post_dec_fx.c
index cbcb225bc1c845d937119028fb6fcc025a19cfeb..02462abbd81ac342597bfd73d41e490ff05ba3c6 100644
--- a/lib_dec/post_dec_fx.c
+++ b/lib_dec/post_dec_fx.c
@@ -606,10 +606,12 @@ void cldfb_synth_set_bandsToZero(
     Word16 realQ1, imagQ1, flag, offset, WBcnt;
     Word16 perc_detect, perc_miss;
     Word16 i, k, tmp1, tmp2, tmp3, tmp, update_perc;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
 #endif
+#endif
 
 
     realQ1 = 0;
@@ -656,8 +658,13 @@ void cldfb_synth_set_bandsToZero(
                 /* use 16-bit precision of real and imag buffers */
                 realQ1 = extract_l( L_shr( rAnalysis[k][i], sub( 31 + 3 - 15, scaleFactor.lb_scale ) ) ); /*31 - (15 + scaleFactor.lb_scale) + 3 )*/
                 imagQ1 = extract_l( L_shr( iAnalysis[k][i], sub( 31 + 3 - 15, scaleFactor.lb_scale ) ) ); /* Q(-3), headroom */
+#ifdef ISSUE_1866_replace_overflow_libdec
+                nrgQ31 = L_mac0_sat( nrgQ31, realQ1, realQ1 );                     //??sat
+                nrgQ31 = L_mac0_sat( nrgQ31, imagQ1, imagQ1 ); /* keep in Q(-6) */ //??sat
+#else
                 nrgQ31 = L_mac0_o( nrgQ31, realQ1, realQ1, &Overflow );
                 nrgQ31 = L_mac0_o( nrgQ31, imagQ1, imagQ1, &Overflow ); /* keep in Q(-6) */
+#endif
             }
             nrg_band[i] = ( nrgQ31 );
             move16();
diff --git a/lib_dec/pvq_core_dec_fx.c b/lib_dec/pvq_core_dec_fx.c
index f9c2db757dffc1b7be48fdc5fb69d973b68c41d8..d3630545f4a2a0c47c10b8b9662cb1c67578b33c 100644
--- a/lib_dec/pvq_core_dec_fx.c
+++ b/lib_dec/pvq_core_dec_fx.c
@@ -477,7 +477,7 @@ static void densitySymbolIndexDecode_fx(
     Word32 acc;
     Word16 alpha = 0;
     move16();
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
@@ -494,8 +494,8 @@ static void densitySymbolIndexDecode_fx(
     sym_freq = L_deposit_l( 1 );
 
     angle = atan2_fx( SQRT_DIM_fx[opp_sz], SQRT_DIM_fx[near_sz] ); // Q13
-#ifdef ISSUE_1796_replace_shl_o
-    angle = shl_sat( angle, 1 );
+#ifdef ISSUE_1866_replace_overflow_libdec
+    angle = shl_sat( angle, 1 ); //??sat
 #else
     angle = shl_o( angle, 1, &Overflow );
 #endif
diff --git a/lib_dec/pvq_decode_fx.c b/lib_dec/pvq_decode_fx.c
index c9ed050a2c2c8f542636bc0822c76817e5e4975a..85d4e355810de2b2e060b081b88ee90293343b6e 100644
--- a/lib_dec/pvq_decode_fx.c
+++ b/lib_dec/pvq_decode_fx.c
@@ -33,9 +33,11 @@ void pvq_decode_fx(
     Word32 L_yy, L_isqrt, L_tmp;
 
     UWord16 u16_tmp;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move16();
+#endif
 #endif
 
     entry = get_size_mpvq_calc_offset_fx( dim, k_val, h_mem ); /* get size & prepare H(adaptive table for entry.size=N_MPVQ(dim,k_val) */
@@ -103,12 +105,13 @@ void pvq_decode_fx(
 
             Mpy_32_16_ss( L_isqrt, shl( y[i], shift_num ), &L_tmp, &u16_tmp ); /*  Q31*Q(0+x)  *2*/
             Mpy_32_16_ss( L_tmp, neg_gain_norm, &L_tmp, &u16_tmp );            /*  Q31*Q(0+x) *Q15 *2*/
-#ifdef ISSUE_1799_replace_L_shr_o
-            L_tmp = L_shr_sat( L_tmp, shift_tot );
+#ifdef ISSUE_1866_replace_overflow_libdec
+            L_tmp = L_shr_sat( L_tmp, shift_tot );                  //??sat
+            xq[i] = round_fx_sat( L_tmp ); /* Q15 , array move   */ //??sat
 #else
             L_tmp = L_shr_o( L_tmp, shift_tot, &Overflow );
-#endif
             xq[i] = round_fx_o( L_tmp, &Overflow ); /* Q15 , array move   */
+#endif
             move16();
         }
     }
diff --git a/lib_dec/swb_tbe_dec_fx.c b/lib_dec/swb_tbe_dec_fx.c
index 09f5eda03dd1dc8c9749aed10a34c460acd378b1..94f18676c5bff23db0c78ccdb3be575f25c73bc6 100644
--- a/lib_dec/swb_tbe_dec_fx.c
+++ b/lib_dec/swb_tbe_dec_fx.c
@@ -634,9 +634,11 @@ void ivas_wb_tbe_dec_fx(
     Word32 dummy2[HILBERT_MEM_SIZE];
     Word16 f, inc;
     Word64 W_tmp;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     TD_BWE_DEC_HANDLE hBWE_TD;
     hBWE_TD = st_fx->hBWE_TD;
@@ -962,10 +964,10 @@ void ivas_wb_tbe_dec_fx(
             n = norm_s( max );
             FOR( i = 0; i < L_FRAME16k / 4; i++ )
             {
-#ifdef ISSUE_1796_replace_shl_o
-                shaped_wb_excitation_frac[i] = shl_sat( shaped_wb_excitation[i], n ); /*Q14*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+                shaped_wb_excitation_frac[i] = shl_sat( shaped_wb_excitation[i], n ); /*Q14*/ //??sat
 #else
-                shaped_wb_excitation_frac[i] = shl_o( shaped_wb_excitation[i], n, &Overflow ); /*Q14*/
+                shaped_wb_excitation_frac[i] = shl_o( shaped_wb_excitation[i], n, &Overflow );             /*Q14*/
 #endif
                 move16();
             }
@@ -974,8 +976,13 @@ void ivas_wb_tbe_dec_fx(
             move32();
             FOR( i = 0; i < L_FRAME16k / 4; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mult_sat( shaped_wb_excitation_frac[i], shaped_wb_excitation_frac[i] ); /*Q29*/ //??sat
+                curr_frame_pow = L_add_sat( curr_frame_pow, L_shr( L_tmp, 7 ) ); /*Q22*/                  //??sat
+#else
                 L_tmp = L_mult_o( shaped_wb_excitation_frac[i], shaped_wb_excitation_frac[i], &Overflow ); /*Q29*/
                 curr_frame_pow = L_add_o( curr_frame_pow, L_shr( L_tmp, 7 ), &Overflow );                  /*Q22*/
+#endif
             }
         }
         curr_frame_pow_exp = add( n, n );
@@ -1169,7 +1176,11 @@ void ivas_wb_tbe_dec_fx(
 
                 L_tmp = Mult_32_16( Lacc, 102 ); /* Q22 */
                 exp = norm_l( L_tmp );
+#ifdef ISSUE_1866_replace_overflow_libdec
+                tmp = round_fx_sat( L_shl( L_tmp, exp ) );
+#else
                 tmp = round_fx_o( L_shl_o( L_tmp, exp, &Overflow ), &Overflow );
+#endif
                 exp = sub( add( exp, 22 ), 30 );
                 tmp = div_s( 16384, tmp );
                 L_tmp = Isqrt_lc( L_deposit_h( tmp ), &exp );                                                       /* Q(31-exp) */
@@ -1285,9 +1296,11 @@ void wb_tbe_dec_fx(
     move16();
     Word32 dummy2[HILBERT_MEM_SIZE];
     Word16 f, inc;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     TD_BWE_DEC_HANDLE hBWE_TD;
     hBWE_TD = st_fx->hBWE_TD;
@@ -1609,10 +1622,10 @@ void wb_tbe_dec_fx(
             n = norm_s( max );
             FOR( i = 0; i < L_FRAME16k / 4; i++ )
             {
-#ifdef ISSUE_1796_replace_shl_o
-                shaped_wb_excitation_frac[i] = shl_sat( shaped_wb_excitation[i], n ); /*Q14*/
+#ifdef ISSUE_1866_replace_overflow_libdec
+                shaped_wb_excitation_frac[i] = shl_sat( shaped_wb_excitation[i], n ); /*Q14*/ //??sat
 #else
-                shaped_wb_excitation_frac[i] = shl_o( shaped_wb_excitation[i], n, &Overflow ); /*Q14*/
+                shaped_wb_excitation_frac[i] = shl_o( shaped_wb_excitation[i], n, &Overflow );             /*Q14*/
 #endif
                 move16();
             }
@@ -1621,8 +1634,13 @@ void wb_tbe_dec_fx(
             move32();
             FOR( i = 0; i < L_FRAME16k / 4; i++ )
             {
+#ifdef ISSUE_1866_replace_overflow_libdec
+                L_tmp = L_mult_sat( shaped_wb_excitation_frac[i], shaped_wb_excitation_frac[i] ); /*Q29*/ //??sat
+                curr_frame_pow = L_add_sat( curr_frame_pow, L_shr( L_tmp, 7 ) ); /*Q22*/                  //??sat
+#else
                 L_tmp = L_mult_o( shaped_wb_excitation_frac[i], shaped_wb_excitation_frac[i], &Overflow ); /*Q29*/
                 curr_frame_pow = L_add_o( curr_frame_pow, L_shr( L_tmp, 7 ), &Overflow );                  /*Q22*/
+#endif
             }
         }
         curr_frame_pow_exp = add( n, n );
@@ -1818,7 +1836,11 @@ void wb_tbe_dec_fx(
 
                 L_tmp = Mult_32_16( Lacc, 102 ); /* Q22 */
                 exp = norm_l( L_tmp );
+#ifdef ISSUE_1866_replace_overflow_libdec
+                tmp = round_fx_sat( L_shl( L_tmp, exp ) ); //??sat
+#else
                 tmp = round_fx_o( L_shl_o( L_tmp, exp, &Overflow ), &Overflow );
+#endif
                 exp = sub( add( exp, 22 ), 30 );
                 tmp = div_s( 16384, tmp );
                 L_tmp = Isqrt_lc( L_deposit_h( tmp ), &exp );                                                       /* Q(31-exp) */
diff --git a/lib_dec/syn_outp_fx.c b/lib_dec/syn_outp_fx.c
index 95b98e8548b69d2c5f854bf40c1215f6bb2257ce..e5557fb99eaa7f8cc959cff5eb0deb0fa7cd9a15 100644
--- a/lib_dec/syn_outp_fx.c
+++ b/lib_dec/syn_outp_fx.c
@@ -67,7 +67,7 @@ void unscale_AGC(
 {
     Word16 i, fac, tmp, frame_fac, max_val;
     Word32 L_tmp;
-#ifndef ISSUE_1796_replace_shl_o
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
@@ -84,8 +84,8 @@ void unscale_AGC(
         max_val = s_max( max_val, abs_s( x[i] ) );
     }
     BASOP_SATURATE_WARNING_OFF_EVS
-#ifdef ISSUE_1796_replace_shl_o
-    tmp = shl_sat( 30000, Qx ); /* saturation can occur here */
+#ifdef ISSUE_1866_replace_overflow_libdec
+    tmp = shl_sat( 30000, Qx ); /* saturation can occur here */ //??sat
 #else
     tmp = shl_o( 30000, Qx, &Overflow ); /* saturation can occur here */
 #endif
diff --git a/lib_dec/tonalMDCTconcealment_fx.c b/lib_dec/tonalMDCTconcealment_fx.c
index 16d445b9161bffc043c4cec8108369159970cae2..0cbecda362dedda3f55e0e61cf98eb02a0d0b320 100644
--- a/lib_dec/tonalMDCTconcealment_fx.c
+++ b/lib_dec/tonalMDCTconcealment_fx.c
@@ -724,9 +724,11 @@ static void ivas_CalcPowerSpecAndDetectTonalComponents_fx(
     Word16 invScaleFactors[FDNS_NPTS];
     Word16 invScaleFactors_exp[FDNS_NPTS];
     Word16 powerSpectrum_exp, tmp_exp, old_exp;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
 
     Word16 nBands;
@@ -857,7 +859,11 @@ static void ivas_CalcPowerSpecAndDetectTonalComponents_fx(
         /* 16 bits are now enough for storing the power spectrum */
         FOR( i = 0; i < nSamples; i++ )
         {
+#ifdef ISSUE_1866_replace_overflow_libdec
+            hTonalMDCTConc->secondLastPowerSpectrum[i] = round_fx_sat( powerSpectrum[i] ); // Q31 - powerSpectrum_exp //??sat
+#else
             hTonalMDCTConc->secondLastPowerSpectrum[i] = round_fx_o( powerSpectrum[i], &Overflow ); // Q31 - powerSpectrum_exp
+#endif
             move32();
         }
 
@@ -882,10 +888,12 @@ static void CalcPowerSpecAndDetectTonalComponents(
     Word16 invScaleFactors[FDNS_NPTS];
     Word16 invScaleFactors_exp[FDNS_NPTS];
     Word16 powerSpectrum_exp, tmp_exp, old_exp;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
 #endif
+#endif
 
 
     nSamples = hTonalMDCTConc->nNonZeroSamples;
@@ -975,7 +983,11 @@ static void CalcPowerSpecAndDetectTonalComponents(
         /* 16 bits are now enough for storing the power spectrum */
         FOR( i = 0; i < nSamples; i++ )
         {
+#ifdef ISSUE_1866_replace_overflow_libdec
+            hTonalMDCTConc->secondLastPowerSpectrum[i] = round_fx_sat( powerSpectrum[i] ); // Q31-powerSpectrum_exp //??sat
+#else
             hTonalMDCTConc->secondLastPowerSpectrum[i] = round_fx_o( powerSpectrum[i], &Overflow ); // Q31-powerSpectrum_exp
+#endif
             move32();
         }
 
diff --git a/lib_dec/transition_dec_fx.c b/lib_dec/transition_dec_fx.c
index 102a81b9d25868024baec7bb8b0019127d3037c5..ace403a84521f982396cf7f60940f5c1c5ede5b0 100644
--- a/lib_dec/transition_dec_fx.c
+++ b/lib_dec/transition_dec_fx.c
@@ -676,9 +676,11 @@ static void tc_dec_fx(
     Word16 j, sc;
     Word16 tempS;
     Word16 index;
+#ifndef ISSUE_1866_replace_overflow_libdec
 #ifdef BASOP_NOGLOB_DECLARE_LOCAL
     Flag Overflow = 0;
     move32();
+#endif
 #endif
     /*----------------------------------------------------------------*
      * find the number of bits
@@ -829,7 +831,11 @@ static void tc_dec_fx(
     j = s_min( L_SUBFR, add( imp_pos, L_IMPULSE2 ) );
     FOR( ; i <= j; i++ )
     {
+#ifdef ISSUE_1866_replace_overflow_libdec
+        exc[i + i_subfr] = round_fx_sat( L_shl_sat( L_mult_sat( pt_shape[i], gain_trans ), sc ) ); /* (Qx * Q14 ) */ //??sat //??sat //??sat
+#else
         exc[i + i_subfr] = round_fx_o( L_shl_o( L_mult_o( pt_shape[i], gain_trans, &Overflow ), sc, &Overflow ), &Overflow ); /* (Qx * Q14 ) */
+#endif
         move16();
     }
     FOR( ; i < L_SUBFR; i++ )