Add MUTABLE_GV(), and eliminate (V *) casts in *.c.

Can't easily do gv.h, as GvGP() (at least) needs to split into two
macros - one const for reading, one non-const for writing.

p4raw-id: //depot/perl@34679

16 files changed, 160 insertions, 151 deletions

diff --git a/doio.c b/doio.c
index 506470504e..aa52f39460 100644
--- a/doio.c
+++ b/doio.c
@@ -906,7 +906,7 @@ Perl_nextargv(pTHX_ register GV *gv)
 	if (io && (IoFLAGS(io) & IOf_ARGV)
 	    && PL_argvout_stack && AvFILLp(PL_argvout_stack) >= 0)
 	{
-	    GV * const oldout = (GV*)av_pop(PL_argvout_stack);
+	    GV * const oldout = MUTABLE_GV(av_pop(PL_argvout_stack));
 	    setdefout(oldout);
 	    SvREFCNT_dec(oldout);
 	    return NULL;
@@ -1308,11 +1308,11 @@ Perl_my_stat(pTHX)
 	STRLEN len;
 	PUTBACK;
 	if (isGV_with_GP(sv)) {
-	    gv = (GV*)sv;
+	    gv = MUTABLE_GV(sv);
 	    goto do_fstat;
 	}
 	else if (SvROK(sv) && isGV_with_GP(SvRV(sv))) {
-	    gv = (GV*)SvRV(sv);
+	    gv = MUTABLE_GV(SvRV(sv));
 	    goto do_fstat;
 	}
         else if (SvROK(sv) && SvTYPE(SvRV(sv)) == SVt_PVIO) {
@@ -1365,7 +1365,7 @@ Perl_my_lstat(pTHX)
     PUTBACK;
     if (SvROK(sv) && isGV_with_GP(SvRV(sv)) && ckWARN(WARN_IO)) {
 	Perl_warner(aTHX_ packWARN(WARN_IO), "Use of -l on filehandle %s",
-		GvENAME((GV*) SvRV(sv)));
+		GvENAME((const GV *)SvRV(sv)));
 	return (PL_laststatval = -1);
     }
     file = SvPV_nolen_const(sv);
@@ -1625,7 +1625,7 @@ Perl_apply(pTHX_ I32 type, register SV **mark, register SV **sp)
 	    while (++mark <= sp) {
                 GV* gv;
                 if (isGV_with_GP(*mark)) {
-                    gv = (GV*)*mark;
+                    gv = MUTABLE_GV(*mark);
 		do_fchmod:
 		    if (GvIO(gv) && IoIFP(GvIOp(gv))) {
 #ifdef HAS_FCHMOD
@@ -1641,7 +1641,7 @@ Perl_apply(pTHX_ I32 type, register SV **mark, register SV **sp)
 		    }
 		}
 		else if (SvROK(*mark) && isGV_with_GP(SvRV(*mark))) {
-		    gv = (GV*)SvRV(*mark);
+		    gv = MUTABLE_GV(SvRV(*mark));
 		    goto do_fchmod;
 		}
 		else {
@@ -1665,7 +1665,7 @@ Perl_apply(pTHX_ I32 type, register SV **mark, register SV **sp)
 	    while (++mark <= sp) {
                 GV* gv;
                 if (isGV_with_GP(*mark)) {
-                    gv = (GV*)*mark;
+                    gv = MUTABLE_GV(*mark);
 		do_fchown:
 		    if (GvIO(gv) && IoIFP(GvIOp(gv))) {
 #ifdef HAS_FCHOWN
@@ -1681,7 +1681,7 @@ Perl_apply(pTHX_ I32 type, register SV **mark, register SV **sp)
 		    }
 		}
 		else if (SvROK(*mark) && isGV_with_GP(SvRV(*mark))) {
-		    gv = (GV*)SvRV(*mark);
+		    gv = MUTABLE_GV(SvRV(*mark));
 		    goto do_fchown;
 		}
 		else {
@@ -1837,7 +1837,7 @@ nothing in the core.
 	    while (++mark <= sp) {
                 GV* gv;
                 if (isGV_with_GP(*mark)) {
-                    gv = (GV*)*mark;
+                    gv = MUTABLE_GV(*mark);
 		do_futimes:
 		    if (GvIO(gv) && IoIFP(GvIOp(gv))) {
 #ifdef HAS_FUTIMES
@@ -1854,7 +1854,7 @@ nothing in the core.
 		    }
 		}
 		else if (SvROK(*mark) && isGV_with_GP(SvRV(*mark))) {
-		    gv = (GV*)SvRV(*mark);
+		    gv = MUTABLE_GV(SvRV(*mark));
 		    goto do_futimes;
 		}
 		else {
diff --git a/dump.c b/dump.c
index 1d2dd2b283..5f899c5d15 100644
--- a/dump.c
+++ b/dump.c
@@ -110,7 +110,7 @@ Perl_dump_packsubs(pTHX_ const HV *stash)
     for (i = 0; i <= (I32) HvMAX(stash); i++) {
         const HE *entry;
 	for (entry = HvARRAY(stash)[i]; entry; entry = HeNEXT(entry)) {
-	    const GV * const gv = (GV*)HeVAL(entry);
+	    const GV * const gv = (const GV *)HeVAL(entry);
 	    if (SvTYPE(gv) != SVt_PVGV || !GvGP(gv))
 		continue;
 	    if (GvCVu(gv))
@@ -1046,7 +1046,7 @@ Perl_do_op_dump(pTHX_ I32 level, PerlIO *file, const OP *o)
 		   UTF-8 cleanliness of the dump file handle?  */
 		SvUTF8_on(tmpsv);
 #endif
-		gv_fullname3(tmpsv, (GV*)cSVOPo->op_sv, NULL);
+		gv_fullname3(tmpsv, MUTABLE_GV(cSVOPo->op_sv), NULL);
 		Perl_dump_indent(aTHX_ level, file, "GV = %s\n",
 				 SvPV_nolen_const(tmpsv));
 		LEAVE;
@@ -2168,7 +2168,7 @@ Perl_xmldump_packsubs(pTHX_ const HV *stash)
 	return;
     for (i = 0; i <= (I32) HvMAX(stash); i++) {
 	for (entry = HvARRAY(stash)[i]; entry; entry = HeNEXT(entry)) {
-	    GV *gv = (GV*)HeVAL(entry);
+	    GV *gv = MUTABLE_GV(HeVAL(entry));
 	    HV *hv;
 	    if (SvTYPE(gv) != SVt_PVGV || !GvGP(gv))
 		continue;
@@ -2832,7 +2832,7 @@ Perl_do_op_xmldump(pTHX_ I32 level, PerlIO *file, const OP *o)
 	    ENTER;
 	    SAVEFREESV(tmpsv1);
 	    SAVEFREESV(tmpsv2);
-	    gv_fullname3(tmpsv1, (GV*)cSVOPo->op_sv, NULL);
+	    gv_fullname3(tmpsv1, MUTABLE_GV(cSVOPo->op_sv), NULL);
 	    s = SvPV(tmpsv1,len);
 	    sv_catxmlpvn(tmpsv2, s, len, 1);
 	    S_xmldump_attr(aTHX_ level, file, "gv=\"%s\"", SvPV(tmpsv2, len));
diff --git a/gv.c b/gv.c
index 4a1617c1c6..eadeb971dc 100644
--- a/gv.c
+++ b/gv.c
@@ -669,7 +669,7 @@ Perl_gv_fetchmethod_flags(pTHX_ HV *stash, const char *name, U32 flags)
     gv = gv_fetchmeth(stash, name, nend - name, 0);
     if (!gv) {
 	if (strEQ(name,"import") || strEQ(name,"unimport"))
-	    gv = (GV*)&PL_sv_yes;
+	    gv = MUTABLE_GV(&PL_sv_yes);
 	else if (autoload)
 	    gv = gv_autoload4(ostash, name, nend - name, TRUE);
 	if (!gv && do_croak) {
@@ -996,7 +996,7 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
 		tmpbuf[len++] = ':';
 		gvp = (GV**)hv_fetch(stash,tmpbuf,len,add);
 		gv = gvp ? *gvp : NULL;
-		if (gv && gv != (GV*)&PL_sv_undef) {
+		if (gv && gv != (const GV *)&PL_sv_undef) {
 		    if (SvTYPE(gv) != SVt_PVGV)
 			gv_init(gv, stash, tmpbuf, len, (add & GV_ADDMULTI));
 		    else
@@ -1004,7 +1004,7 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
 		}
 		if (tmpbuf != smallbuf)
 		    Safefree(tmpbuf);
-		if (!gv || gv == (GV*)&PL_sv_undef)
+		if (!gv || gv == (const GV *)&PL_sv_undef)
 		    return NULL;
 
 		if (!(stash = GvHV(gv)))
@@ -1019,7 +1019,8 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
 	    name_cursor++;
 	    name = name_cursor;
 	    if (name == name_end)
-		return gv ? gv : (GV*)*hv_fetchs(PL_defstash, "main::", TRUE);
+		return gv
+		    ? gv : MUTABLE_GV(*hv_fetchs(PL_defstash, "main::", TRUE));
 	}
     }
     len = name_cursor - name;
@@ -1080,7 +1081,7 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
 		{
 		    gvp = (GV**)hv_fetch(stash,name,len,0);
 		    if (!gvp ||
-			*gvp == (GV*)&PL_sv_undef ||
+			*gvp == (const GV *)&PL_sv_undef ||
 			SvTYPE(*gvp) != SVt_PVGV)
 		    {
 			stash = NULL;
@@ -1135,7 +1136,7 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
 	return NULL;
 
     gvp = (GV**)hv_fetch(stash,name,len,add);
-    if (!gvp || *gvp == (GV*)&PL_sv_undef)
+    if (!gvp || *gvp == (const GV *)&PL_sv_undef)
 	return NULL;
     gv = *gvp;
     if (SvTYPE(gv) == SVt_PVGV) {
@@ -1532,14 +1533,14 @@ Perl_gv_check(pTHX_ const HV *stash)
             register GV *gv;
             HV *hv;
 	    if (HeKEY(entry)[HeKLEN(entry)-1] == ':' &&
-		(gv = (GV*)HeVAL(entry)) && isGV(gv) && (hv = GvHV(gv)))
+		(gv = MUTABLE_GV(HeVAL(entry))) && isGV(gv) && (hv = GvHV(gv)))
 	    {
 		if (hv != PL_defstash && hv != stash)
 		     gv_check(hv);              /* nested package */
 	    }
 	    else if (isALPHA(*HeKEY(entry))) {
                 const char *file;
-		gv = (GV*)HeVAL(entry);
+		gv = MUTABLE_GV(HeVAL(entry));
 		if (SvTYPE(gv) != SVt_PVGV || GvMULTI(gv))
 		    continue;
 		file = GvFILE(gv);
diff --git a/handy.h b/handy.h
index d488922a44..d4b8ac292b 100644
--- a/handy.h
+++ b/handy.h
@@ -56,6 +56,7 @@ Null SV pointer. (No longer available when C<PERL_CORE> is defined.)
 
 #define MUTABLE_AV(p)	((AV *)MUTABLE_PTR(p))
 #define MUTABLE_CV(p)	((CV *)MUTABLE_PTR(p))
+#define MUTABLE_GV(p)	((GV *)MUTABLE_PTR(p))
 #define MUTABLE_HV(p)	((HV *)MUTABLE_PTR(p))
 #define MUTABLE_IO(p)	((IO *)MUTABLE_PTR(p))
 #define MUTABLE_SV(p)	((SV *)MUTABLE_PTR(p))
diff --git a/mg.c b/mg.c
index 39313aa98d..e1438feb51 100644
--- a/mg.c
+++ b/mg.c
@@ -919,7 +919,7 @@ Perl_magic_get(pTHX_ SV *sv, MAGIC *mg)
     case '5': case '6': case '7': case '8': case '9': case '&':
 	    if (PL_curpm && (rx = PM_GETRE(PL_curpm))) {
 		/*
-		 * Pre-threads, this was paren = atoi(GvENAME((GV*)mg->mg_obj));
+		 * Pre-threads, this was paren = atoi(GvENAME((const GV *)mg->mg_obj));
 		 * XXX Does the new way break anything?
 		 */
 		paren = atoi(mg->mg_ptr); /* $& is in [0] */
@@ -1582,8 +1582,8 @@ Perl_magic_setisa(pTHX_ SV *sv, MAGIC *mg)
        calls this same magic */
     stash = GvSTASH(
         SvTYPE(mg->mg_obj) == SVt_PVGV
-            ? (GV*)mg->mg_obj
-            : (GV*)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
+            ? (const GV *)mg->mg_obj
+            : (const GV *)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
     );
 
     if (stash)
@@ -1608,8 +1608,8 @@ Perl_magic_clearisa(pTHX_ SV *sv, MAGIC *mg)
     /* XXX see comments in magic_setisa */
     stash = GvSTASH(
         SvTYPE(mg->mg_obj) == SVt_PVGV
-            ? (GV*)mg->mg_obj
-            : (GV*)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
+            ? (const GV *)mg->mg_obj
+            : (const GV *)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
     );
 
     if (stash)
diff --git a/op.c b/op.c
index b70d502346..19d834fcb0 100644
--- a/op.c
+++ b/op.c
@@ -2563,7 +2563,7 @@ Perl_fold_constants(pTHX_ register OP *o)
 #endif
     assert(sv);
     if (type == OP_RV2GV)
-	newop = newGVOP(OP_GV, 0, (GV*)sv);
+	newop = newGVOP(OP_GV, 0, MUTABLE_GV(sv));
     else
 	newop = newSVOP(OP_CONST, 0, MUTABLE_SV(sv));
     op_getmad(o,newop,'f');
@@ -4264,7 +4264,7 @@ Perl_newASSIGNOP(pTHX_ I32 flags, OP *left, I32 optype, OP *right)
 		    else if (curop->op_type == OP_PUSHRE) {
 #ifdef USE_ITHREADS
 			if (((PMOP*)curop)->op_pmreplrootu.op_pmtargetoff) {
-			    GV *const gv = (GV*)PAD_SVl(((PMOP*)curop)->op_pmreplrootu.op_pmtargetoff);
+			    GV *const gv = MUTABLE_GV(PAD_SVl(((PMOP*)curop)->op_pmreplrootu.op_pmtargetoff));
 			    if (gv == PL_defgv
 				|| (int)GvASSIGN_GENERATION(gv) == PL_generation)
 				break;
@@ -4312,7 +4312,7 @@ Perl_newASSIGNOP(pTHX_ I32 flags, OP *left, I32 optype, OP *right)
 			cPADOPx(tmpop)->op_padix = 0;	/* steal it */
 #else
 			pm->op_pmreplrootu.op_pmtargetgv
-			    = (GV*)cSVOPx(tmpop)->op_sv;
+			    = MUTABLE_GV(cSVOPx(tmpop)->op_sv);
 			cSVOPx(tmpop)->op_sv = NULL;	/* steal it */
 #endif
 			pm->op_pmflags |= PMf_ONCE;
diff --git a/perlio.c b/perlio.c
index e2d64d49bd..f0534bd436 100644
--- a/perlio.c
+++ b/perlio.c
@@ -832,7 +832,7 @@ static int
 perlio_mg_set(pTHX_ SV *sv, MAGIC *mg)
 {
     if (SvROK(sv)) {
-	IO * const io = GvIOn((GV *) SvRV(sv));
+	IO * const io = GvIOn(MUTABLE_GV(SvRV(sv)));
 	PerlIO * const ifp = IoIFP(io);
 	PerlIO * const ofp = IoOFP(io);
 	Perl_warn(aTHX_ "set %" SVf " %p %p %p",
@@ -845,7 +845,7 @@ static int
 perlio_mg_get(pTHX_ SV *sv, MAGIC *mg)
 {
     if (SvROK(sv)) {
-	IO * const io = GvIOn((GV *) SvRV(sv));
+	IO * const io = GvIOn(MUTABLE_GV(SvRV(sv)));
 	PerlIO * const ifp = IoIFP(io);
 	PerlIO * const ofp = IoOFP(io);
 	Perl_warn(aTHX_ "get %" SVf " %p %p %p",
diff --git a/pp.c b/pp.c
index 5c83f3242c..5b16f25862 100644
--- a/pp.c
+++ b/pp.c
@@ -137,7 +137,7 @@ PP(pp_rv2gv)
 
 	sv = SvRV(sv);
 	if (SvTYPE(sv) == SVt_PVIO) {
-	    GV * const gv = (GV*) sv_newmortal();
+	    GV * const gv = MUTABLE_GV(sv_newmortal());
 	    gv_init(gv, 0, "", 0, 0);
 	    GvIOp(gv) = MUTABLE_IO(sv);
 	    SvREFCNT_inc_void_NN(sv);
@@ -165,7 +165,7 @@ PP(pp_rv2gv)
 			STRLEN len;
 			SV * const namesv = PAD_SV(cUNOP->op_targ);
 			const char * const name = SvPV(namesv, len);
-			gv = (GV*)newSV(0);
+			gv = MUTABLE_GV(newSV(0));
 			gv_init(gv, CopSTASH(PL_curcop), name, len, 0);
 		    }
 		    else {
@@ -212,7 +212,7 @@ PP(pp_rv2gv)
 	}
     }
     if (PL_op->op_private & OPpLVAL_INTRO)
-	save_gp((GV*)sv, !(PL_op->op_flags & OPf_SPECIAL));
+	save_gp(MUTABLE_GV(sv), !(PL_op->op_flags & OPf_SPECIAL));
     SETs(sv);
     RETURN;
 }
@@ -284,7 +284,7 @@ PP(pp_rv2sv)
 	}
     }
     else {
-	gv = (GV*)sv;
+	gv = MUTABLE_GV(sv);
 
 	if (!isGV_with_GP(gv)) {
 	    if (SvGMAGICAL(sv)) {
@@ -301,7 +301,7 @@ PP(pp_rv2sv)
     if (PL_op->op_flags & OPf_MOD) {
 	if (PL_op->op_private & OPpLVAL_INTRO) {
 	    if (cUNOP->op_first->op_type == OP_NULL)
-		sv = save_scalar((GV*)TOPs);
+		sv = save_scalar(MUTABLE_GV(TOPs));
 	    else if (gv)
 		sv = save_scalar(gv);
 	    else
@@ -589,7 +589,7 @@ PP(pp_gelem)
 
     SV *sv = POPs;
     const char * const elem = SvPV_nolen_const(sv);
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     SV * tmpRef = NULL;
 
     sv = NULL;
@@ -833,18 +833,19 @@ PP(pp_undef)
             HV *stash;
 
             /* undef *Foo:: */
-            if((stash = GvHV((GV*)sv)) && HvNAME_get(stash))
+            if((stash = GvHV((const GV *)sv)) && HvNAME_get(stash))
                 mro_isa_changed_in(stash);
             /* undef *Pkg::meth_name ... */
-            else if(GvCVu((GV*)sv) && (stash = GvSTASH((GV*)sv)) && HvNAME_get(stash))
+            else if(GvCVu((const GV *)sv) && (stash = GvSTASH((const GV *)sv))
+		    && HvNAME_get(stash))
                 mro_method_changed_in(stash);
 
-	    gp_free((GV*)sv);
+	    gp_free(MUTABLE_GV(sv));
 	    Newxz(gp, 1, GP);
 	    GvGP(sv) = gp_ref(gp);
 	    GvSV(sv) = newSV(0);
 	    GvLINE(sv) = CopLINE(PL_curcop);
-	    GvEGV(sv) = (GV*)sv;
+	    GvEGV(sv) = MUTABLE_GV(sv);
 	    GvMULTI_on(sv);
 	    break;
 	}
@@ -4178,7 +4179,7 @@ PP(pp_hslice)
             }
             if (localizing) {
 		if (HvNAME_get(hv) && isGV(*svp))
-		    save_gp((GV*)*svp, !(PL_op->op_flags & OPf_SPECIAL));
+		    save_gp(MUTABLE_GV(*svp), !(PL_op->op_flags & OPf_SPECIAL));
 		else {
 		    if (preeminent)
 			save_helem(hv, keysv, svp);
@@ -4704,7 +4705,7 @@ PP(pp_split)
 
 #ifdef USE_ITHREADS
     if (pm->op_pmreplrootu.op_pmtargetoff) {
-	ary = GvAVn((GV*)PAD_SVl(pm->op_pmreplrootu.op_pmtargetoff));
+	ary = GvAVn(MUTABLE_GV(PAD_SVl(pm->op_pmreplrootu.op_pmtargetoff)));
     }
 #else
     if (pm->op_pmreplrootu.op_pmtargetgv) {
diff --git a/pp_ctl.c b/pp_ctl.c
index 052eea4646..8351d53055 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -1894,7 +1894,7 @@ PP(pp_enteriter)
 #endif
     }
     else {
-	GV * const gv = (GV*)POPs;
+	GV * const gv = MUTABLE_GV(POPs);
 	svp = &GvSV(gv);			/* symbol table variable */
 	SAVEGENERICSV(*svp);
 	*svp = newSV(0);
@@ -3383,7 +3383,7 @@ PP(pp_require)
 			}
 
 			if (isGV_with_GP(arg)) {
-			    IO * const io = GvIO((GV *)arg);
+			    IO * const io = GvIO((const GV *)arg);
 
 			    ++filter_has_file;
 
@@ -3601,9 +3601,9 @@ PP(pp_require)
     if (filter_sub || filter_cache) {
 	SV * const datasv = filter_add(S_run_user_filter, NULL);
 	IoLINES(datasv) = filter_has_file;
-	IoTOP_GV(datasv) = (GV *)filter_state;
-	IoBOTTOM_GV(datasv) = (GV *)filter_sub;
-	IoFMT_GV(datasv) = (GV *)filter_cache;
+	IoTOP_GV(datasv) = MUTABLE_GV(filter_state);
+	IoBOTTOM_GV(datasv) = MUTABLE_GV(filter_sub);
+	IoFMT_GV(datasv) = MUTABLE_GV(filter_cache);
     }
 
     /* switch to eval mode */
@@ -4861,7 +4861,7 @@ S_run_user_filter(pTHX_ int idx, SV *buf_sv, int maxlen)
 	SV *cache = MUTABLE_SV(IoFMT_GV(datasv));
 
 	if (!cache) {
-	    IoFMT_GV(datasv) = (GV*) (cache = newSV(got_len - umaxlen));
+	    IoFMT_GV(datasv) = MUTABLE_GV((cache = newSV(got_len - umaxlen)));
 	} else if (SvOK(cache)) {
 	    /* Cache should be empty.  */
 	    assert(!SvCUR(cache));
diff --git a/pp_hot.c b/pp_hot.c
index c86762ee77..e602c87143 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -180,7 +180,7 @@ PP(pp_sassign)
 		   So change the reference so that it points to the subroutine
 		   of that typeglob, as that's what they were after all along.
 		*/
-		GV *const upgraded = (GV *) cv;
+		GV *const upgraded = MUTABLE_GV(cv);
 		CV *const source = GvCV(upgraded);
 
 		assert(source);
@@ -306,16 +306,16 @@ PP(pp_readline)
 {
     dVAR;
     tryAMAGICunTARGET(iter, 0);
-    PL_last_in_gv = (GV*)(*PL_stack_sp--);
+    PL_last_in_gv = MUTABLE_GV(*PL_stack_sp--);
     if (!isGV_with_GP(PL_last_in_gv)) {
 	if (SvROK(PL_last_in_gv) && isGV_with_GP(SvRV(PL_last_in_gv)))
-	    PL_last_in_gv = (GV*)SvRV(PL_last_in_gv);
+	    PL_last_in_gv = MUTABLE_GV(SvRV(PL_last_in_gv));
 	else {
 	    dSP;
 	    XPUSHs(MUTABLE_SV(PL_last_in_gv));
 	    PUTBACK;
 	    pp_rv2gv();
-	    PL_last_in_gv = (GV*)(*PL_stack_sp--);
+	    PL_last_in_gv = MUTABLE_GV(*PL_stack_sp--);
 	}
     }
     return do_readline();
@@ -698,7 +698,8 @@ PP(pp_print)
     IO *io;
     register PerlIO *fp;
     MAGIC *mg;
-    GV * const gv = (PL_op->op_flags & OPf_STACKED) ? (GV*)*++MARK : PL_defoutgv;
+    GV * const gv
+	= (PL_op->op_flags & OPf_STACKED) ? MUTABLE_GV(*++MARK) : PL_defoutgv;
 
     if (gv && (io = GvIO(gv))
 	&& (mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar)))
@@ -855,7 +856,7 @@ PP(pp_rv2av)
 		    RETURN;
 	    }
 	    else {
-		gv = (GV*)sv;
+		gv = MUTABLE_GV(sv);
 	    }
 	    sv = is_pp_rv2av ? MUTABLE_SV(GvAVn(gv)) : MUTABLE_SV(GvHVn(gv));
 	    if (PL_op->op_private & OPpLVAL_INTRO)
@@ -1817,7 +1818,7 @@ PP(pp_helem)
 	}
 	if (PL_op->op_private & OPpLVAL_INTRO) {
 	    if (HvNAME_get(hv) && isGV(*svp))
-		save_gp((GV*)*svp, !(PL_op->op_flags & OPf_SPECIAL));
+		save_gp(MUTABLE_GV(*svp), !(PL_op->op_flags & OPf_SPECIAL));
 	    else {
 		if (!preeminent) {
 		    STRLEN keylen;
@@ -2668,7 +2669,7 @@ PP(pp_entersub)
     case SVt_PVGV:
 	if (!isGV_with_GP(sv))
 	    DIE(aTHX_ "Not a CODE reference");
-	if (!(cv = GvCVu((GV*)sv))) {
+	if (!(cv = GvCVu((const GV *)sv))) {
 	    HV *stash;
 	    cv = sv_2cv(sv, &stash, &gv, 0);
 	}
@@ -3079,7 +3080,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
     if (!ob || !(SvOBJECT(ob)
 		 || (SvTYPE(ob) == SVt_PVGV 
 		     && isGV_with_GP(ob)
-		     && (ob = MUTABLE_SV(GvIO((GV*)ob)))
+		     && (ob = MUTABLE_SV(GvIO((const GV *)ob)))
 		     && SvOBJECT(ob))))
     {
 	Perl_croak(aTHX_ "Can't call method \"%s\" on unblessed reference",
@@ -3097,7 +3098,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
     if (hashp) {
 	const HE* const he = hv_fetch_ent(stash, meth, 0, *hashp);
 	if (he) {
-	    gv = (GV*)HeVAL(he);
+	    gv = MUTABLE_GV(HeVAL(he));
 	    if (isGV(gv) && GvCV(gv) &&
 		(!GvCVGEN(gv) || GvCVGEN(gv)
                   == (PL_sub_generation + HvMROMETA(stash)->cache_gen)))
diff --git a/pp_sys.c b/pp_sys.c
index 8e1c8cd603..de4d692bd4 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -385,7 +385,7 @@ PP(pp_glob)
 #endif /* !VMS */
 
     SAVESPTR(PL_last_in_gv);	/* We don't want this to be permanent. */
-    PL_last_in_gv = (GV*)*PL_stack_sp--;
+    PL_last_in_gv = MUTABLE_GV(*PL_stack_sp--);
 
     SAVESPTR(PL_rs);		/* This is not permanent, either. */
     PL_rs = newSVpvs_flags("\000", SVs_TEMP);
@@ -519,7 +519,7 @@ PP(pp_open)
     STRLEN len;
     bool  ok;
 
-    GV * const gv = (GV *)*++MARK;
+    GV * const gv = MUTABLE_GV(*++MARK);
 
     if (!isGV(gv))
 	DIE(aTHX_ PL_no_usym, "filehandle");
@@ -569,7 +569,7 @@ PP(pp_open)
 PP(pp_close)
 {
     dVAR; dSP;
-    GV * const gv = (MAXARG == 0) ? PL_defoutgv : (GV*)POPs;
+    GV * const gv = (MAXARG == 0) ? PL_defoutgv : MUTABLE_GV(POPs);
 
     if (gv) {
 	IO * const io = GvIO(gv);
@@ -601,8 +601,8 @@ PP(pp_pipe_op)
     register IO *wstio;
     int fd[2];
 
-    GV * const wgv = (GV*)POPs;
-    GV * const rgv = (GV*)POPs;
+    GV * const wgv = MUTABLE_GV(POPs);
+    GV * const rgv = MUTABLE_GV(POPs);
 
     if (!rgv || !wgv)
 	goto badexit;
@@ -661,7 +661,7 @@ PP(pp_fileno)
 
     if (MAXARG < 1)
 	RETPUSHUNDEF;
-    gv = (GV*)POPs;
+    gv = MUTABLE_GV(POPs);
 
     if (gv && (io = GvIO(gv))
 	&& (mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar)))
@@ -734,7 +734,7 @@ PP(pp_binmode)
 	discp = POPs;
     }
 
-    gv = (GV*)POPs;
+    gv = MUTABLE_GV(POPs);
 
     if (gv && (io = GvIO(gv))) {
 	MAGIC * const mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar);
@@ -808,7 +808,7 @@ PP(pp_tie)
 	case SVt_PVGV:
 	    if (isGV_with_GP(varsv)) {
 #ifdef GV_UNIQUE_CHECK
-		if (GvUNIQUE((GV*)varsv)) {
+		if (GvUNIQUE((const GV *)varsv)) {
 		    Perl_croak(aTHX_ "Attempt to tie unique GV");
 		}
 #endif
@@ -1168,7 +1168,7 @@ PP(pp_select)
 {
     dVAR; dSP; dTARGET;
     HV *hv;
-    GV * const newdefout = (PL_op->op_private > 0) ? ((GV *) POPs) : NULL;
+    GV * const newdefout = (PL_op->op_private > 0) ? (MUTABLE_GV(POPs)) : NULL;
     GV * egv = GvEGV(PL_defoutgv);
 
     if (!egv)
@@ -1200,7 +1200,7 @@ PP(pp_getc)
 {
     dVAR; dSP; dTARGET;
     IO *io = NULL;
-    GV * const gv = (MAXARG==0) ? PL_stdingv : (GV*)POPs;
+    GV * const gv = (MAXARG==0) ? PL_stdingv : MUTABLE_GV(POPs);
 
     if (gv && (io = GvIO(gv))) {
 	MAGIC * const mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar);
@@ -1276,7 +1276,7 @@ PP(pp_enterwrite)
     if (MAXARG == 0)
 	gv = PL_defoutgv;
     else {
-	gv = (GV*)POPs;
+	gv = MUTABLE_GV(POPs);
 	if (!gv)
 	    gv = PL_defoutgv;
     }
@@ -1447,7 +1447,8 @@ PP(pp_prtf)
     PerlIO *fp;
     SV *sv;
 
-    GV * const gv = (PL_op->op_flags & OPf_STACKED) ? (GV*)*++MARK : PL_defoutgv;
+    GV * const gv
+	= (PL_op->op_flags & OPf_STACKED) ? MUTABLE_GV(*++MARK) : PL_defoutgv;
 
     if (gv && (io = GvIO(gv))) {
 	MAGIC * const mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar);
@@ -1519,7 +1520,7 @@ PP(pp_sysopen)
     const int perm = (MAXARG > 3) ? POPi : 0666;
     const int mode = POPi;
     SV * const sv = POPs;
-    GV * const gv = (GV *)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     STRLEN len;
 
     /* Need TIEHANDLE method ? */
@@ -1555,7 +1556,7 @@ PP(pp_sysread)
     STRLEN charskip = 0;
     STRLEN skip = 0;
 
-    GV * const gv = (GV*)*++MARK;
+    GV * const gv = MUTABLE_GV(*++MARK);
     if ((PL_op->op_type == OP_READ || PL_op->op_type == OP_SYSREAD)
 	&& gv && (io = GvIO(gv)) )
     {
@@ -1801,7 +1802,7 @@ PP(pp_send)
     bool doing_utf8;
     U8 *tmpbuf = NULL;
     
-    GV *const gv = (GV*)*++MARK;
+    GV *const gv = MUTABLE_GV(*++MARK);
     if (PL_op->op_type == OP_SYSWRITE
 	&& gv && (io = GvIO(gv))) {
 	MAGIC * const mg = SvTIED_mg((const SV *)io, PERL_MAGIC_tiedscalar);
@@ -2038,7 +2039,7 @@ PP(pp_eof)
 	    gv = PL_last_in_gv;			/* eof */
     }
     else
-	gv = PL_last_in_gv = (GV*)POPs;		/* eof(FH) */
+	gv = PL_last_in_gv = MUTABLE_GV(POPs);	/* eof(FH) */
 
     if (gv) {
 	IO * const io = GvIO(gv);
@@ -2066,7 +2067,7 @@ PP(pp_tell)
     IO *io;
 
     if (MAXARG != 0)
-	PL_last_in_gv = (GV*)POPs;
+	PL_last_in_gv = MUTABLE_GV(POPs);
     gv = PL_last_in_gv;
 
     if (gv && (io = GvIO(gv))) {
@@ -2101,7 +2102,7 @@ PP(pp_sysseek)
     const Off_t offset = (Off_t)SvIVx(POPs);
 #endif
 
-    GV * const gv = PL_last_in_gv = (GV*)POPs;
+    GV * const gv = PL_last_in_gv = MUTABLE_GV(POPs);
     IO *io;
 
     if (gv && (io = GvIO(gv))) {
@@ -2199,11 +2200,11 @@ PP(pp_truncate)
 	    const char *name;
 
 	    if (isGV_with_GP(sv)) {
-	        tmpgv = (GV*)sv;		/* *main::FRED for example */
+	        tmpgv = MUTABLE_GV(sv);		/* *main::FRED for example */
 		goto do_ftruncate_gv;
 	    }
 	    else if (SvROK(sv) && isGV_with_GP(SvRV(sv))) {
-	        tmpgv = (GV*) SvRV(sv);	/* \*main::FRED for example */
+	        tmpgv = MUTABLE_GV(SvRV(sv));	/* \*main::FRED for example */
 		goto do_ftruncate_gv;
 	    }
 	    else if (SvROK(sv) && SvTYPE(SvRV(sv)) == SVt_PVIO) {
@@ -2245,7 +2246,7 @@ PP(pp_ioctl)
     SV * const argsv = POPs;
     const unsigned int func = POPu;
     const int optype = PL_op->op_type;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     IO * const io = gv ? GvIOn(gv) : NULL;
     char *s;
     IV retval;
@@ -2322,7 +2323,7 @@ PP(pp_flock)
     IO *io = NULL;
     PerlIO *fp;
     const int argtype = POPi;
-    GV * const gv = (MAXARG == 0) ? PL_last_in_gv : (GV*)POPs;
+    GV * const gv = (MAXARG == 0) ? PL_last_in_gv : MUTABLE_GV(POPs);
 
     if (gv && (io = GvIO(gv)))
 	fp = IoIFP(io);
@@ -2357,7 +2358,7 @@ PP(pp_socket)
     const int protocol = POPi;
     const int type = POPi;
     const int domain = POPi;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = gv ? GvIOn(gv) : NULL;
     int fd;
 
@@ -2407,8 +2408,8 @@ PP(pp_sockpair)
     const int protocol = POPi;
     const int type = POPi;
     const int domain = POPi;
-    GV * const gv2 = (GV*)POPs;
-    GV * const gv1 = (GV*)POPs;
+    GV * const gv2 = MUTABLE_GV(POPs);
+    GV * const gv1 = MUTABLE_GV(POPs);
     register IO * const io1 = gv1 ? GvIOn(gv1) : NULL;
     register IO * const io2 = gv2 ? GvIOn(gv2) : NULL;
     int fd[2];
@@ -2468,7 +2469,7 @@ PP(pp_bind)
     SV * const addrsv = POPs;
     /* OK, so on what platform does bind modify addr?  */
     const char *addr;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
     STRLEN len;
 
@@ -2497,7 +2498,7 @@ PP(pp_connect)
 #ifdef HAS_SOCKET
     dVAR; dSP;
     SV * const addrsv = POPs;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
     const char *addr;
     STRLEN len;
@@ -2527,7 +2528,7 @@ PP(pp_listen)
 #ifdef HAS_SOCKET
     dVAR; dSP;
     const int backlog = POPi;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = gv ? GvIOn(gv) : NULL;
 
     if (!gv || !io || !IoIFP(io))
@@ -2560,8 +2561,8 @@ PP(pp_accept)
 #else
     Sock_size_t len = sizeof namebuf;
 #endif
-    GV * const ggv = (GV*)POPs;
-    GV * const ngv = (GV*)POPs;
+    GV * const ggv = MUTABLE_GV(POPs);
+    GV * const ngv = MUTABLE_GV(POPs);
     int fd;
 
     if (!ngv)
@@ -2632,7 +2633,7 @@ PP(pp_shutdown)
 #ifdef HAS_SOCKET
     dVAR; dSP; dTARGET;
     const int how = POPi;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
 
     if (!io || !IoIFP(io))
@@ -2659,7 +2660,7 @@ PP(pp_ssockopt)
     SV * const sv = (optype == OP_GSOCKOPT) ? sv_2mortal(newSV(257)) : POPs;
     const unsigned int optname = (unsigned int) POPi;
     const unsigned int lvl = (unsigned int) POPi;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
     int fd;
     Sock_size_t len;
@@ -2733,7 +2734,7 @@ PP(pp_getpeername)
 #ifdef HAS_SOCKET
     dVAR; dSP;
     const int optype = PL_op->op_type;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
     Sock_size_t len;
     SV *sv;
@@ -2846,10 +2847,10 @@ PP(pp_stat)
     else {
 	SV* const sv = POPs;
 	if (isGV_with_GP(sv)) {
-	    gv = (GV*)sv;
+	    gv = MUTABLE_GV(sv);
 	    goto do_fstat;
 	} else if(SvROK(sv) && isGV_with_GP(SvRV(sv))) {
-            gv = (GV*)SvRV(sv);
+            gv = MUTABLE_GV(SvRV(sv));
             if (PL_op->op_type == OP_LSTAT)
                 goto do_fstat_warning_check;
             goto do_fstat;
@@ -3204,9 +3205,9 @@ PP(pp_fttty)
     if (PL_op->op_flags & OPf_REF)
 	gv = cGVOP_gv;
     else if (isGV(TOPs))
-	gv = (GV*)POPs;
+	gv = MUTABLE_GV(POPs);
     else if (SvROK(TOPs) && isGV(SvRV(TOPs)))
-	gv = (GV*)SvRV(POPs);
+	gv = MUTABLE_GV(SvRV(POPs));
     else
 	gv = gv_fetchsv(tmpsv = POPs, 0, SVt_PVIO);
 
@@ -3253,9 +3254,9 @@ PP(pp_fttext)
     if (PL_op->op_flags & OPf_REF)
 	gv = cGVOP_gv;
     else if (isGV(TOPs))
-	gv = (GV*)POPs;
+	gv = MUTABLE_GV(POPs);
     else if (SvROK(TOPs) && isGV(SvRV(TOPs)))
-	gv = (GV*)SvRV(POPs);
+	gv = MUTABLE_GV(SvRV(POPs));
     else
 	gv = NULL;
 
@@ -3405,10 +3406,10 @@ PP(pp_chdir)
 	    gv = gv_fetchsv(sv, 0, SVt_PVIO);
 	}
         else if (isGV_with_GP(sv)) {
-	    gv = (GV*)sv;
+	    gv = MUTABLE_GV(sv);
         }
 	else if (SvROK(sv) && isGV_with_GP(SvRV(sv))) {
-            gv = (GV*)SvRV(sv);
+            gv = MUTABLE_GV(SvRV(sv));
         }
         else {
 	    tmps = SvPV_nolen_const(sv);
@@ -3761,7 +3762,7 @@ PP(pp_open_dir)
 #if defined(Direntry_t) && defined(HAS_READDIR)
     dVAR; dSP;
     const char * const dirname = POPpconstx;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
 
     if (!io)
@@ -3798,7 +3799,7 @@ PP(pp_readdir)
 
     SV *sv;
     const I32 gimme = GIMME;
-    GV * const gv = (GV *)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register const Direntry_t *dp;
     register IO * const io = GvIOn(gv);
 
@@ -3852,7 +3853,7 @@ PP(pp_telldir)
 # if !defined(HAS_TELLDIR_PROTO) || defined(NEED_TELLDIR_PROTO)
     long telldir (DIR *);
 # endif
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
 
     if (!io || !IoDIRP(io)) {
@@ -3879,7 +3880,7 @@ PP(pp_seekdir)
 #if defined(HAS_SEEKDIR) || defined(seekdir)
     dVAR; dSP;
     const long along = POPl;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
 
     if (!io || !IoDIRP(io)) {
@@ -3905,7 +3906,7 @@ PP(pp_rewinddir)
 {
 #if defined(HAS_REWINDDIR) || defined(rewinddir)
     dVAR; dSP;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
 
     if (!io || !IoDIRP(io)) {
@@ -3930,7 +3931,7 @@ PP(pp_closedir)
 {
 #if defined(Direntry_t) && defined(HAS_READDIR)
     dVAR; dSP;
-    GV * const gv = (GV*)POPs;
+    GV * const gv = MUTABLE_GV(POPs);
     register IO * const io = GvIOn(gv);
 
     if (!io || !IoDIRP(io)) {
diff --git a/scope.c b/scope.c
index 6e74978aeb..4b900efe49 100644
--- a/scope.c
+++ b/scope.c
@@ -710,7 +710,7 @@ Perl_leave_scope(pTHX_ I32 base)
 	    break;
 	case SAVEt_SV:				/* scalar reference */
 	    value = MUTABLE_SV(SSPOPPTR);
-	    gv = (GV*)SSPOPPTR;
+	    gv = MUTABLE_GV(SSPOPPTR);
 	    ptr = &GvSV(gv);
 	    av = MUTABLE_AV(gv); /* what to refcnt_dec */
 	restore_sv:
@@ -754,7 +754,7 @@ Perl_leave_scope(pTHX_ I32 base)
 	    break;
 	case SAVEt_AV:				/* array reference */
 	    av = MUTABLE_AV(SSPOPPTR);
-	    gv = (GV*)SSPOPPTR;
+	    gv = MUTABLE_GV(SSPOPPTR);
 	    if (GvAV(gv)) {
 		SvREFCNT_dec(GvAV(gv));
 	    }
@@ -767,7 +767,7 @@ Perl_leave_scope(pTHX_ I32 base)
 	    break;
 	case SAVEt_HV:				/* hash reference */
 	    hv = MUTABLE_HV(SSPOPPTR);
-	    gv = (GV*)SSPOPPTR;
+	    gv = MUTABLE_GV(SSPOPPTR);
 	    if (GvHV(gv)) {
 		SvREFCNT_dec(GvHV(gv));
 	    }
@@ -817,7 +817,7 @@ Perl_leave_scope(pTHX_ I32 base)
 	    break;
 	case SAVEt_GP:				/* scalar reference */
 	    ptr = SSPOPPTR;
-	    gv = (GV*)SSPOPPTR;
+	    gv = MUTABLE_GV(SSPOPPTR);
 	    gp_free(gv);
 	    GvGP(gv) = (GP*)ptr;
             /* putting a method back into circulation ("local")*/
@@ -1048,7 +1048,7 @@ Perl_leave_scope(pTHX_ I32 base)
 
 	    /* These are only saved in mathoms.c */
 	case SAVEt_NSTAB:
-	    gv = (GV*)SSPOPPTR;
+	    gv = MUTABLE_GV(SSPOPPTR);
 	    (void)sv_clear(MUTABLE_SV(gv));
 	    break;
 	case SAVEt_LONG:			/* long reference */
diff --git a/sv.c b/sv.c
index a425a5b9a5..522668eb23 100644
--- a/sv.c
+++ b/sv.c
@@ -2264,7 +2264,7 @@ S_sv_2iuv_common(pTHX_ SV *const sv)
     }
     else  {
 	if (isGV_with_GP(sv))
-	    return glob_2number((GV *)sv);
+	    return glob_2number(MUTABLE_GV(sv));
 
 	if (!(SvFLAGS(sv) & SVs_PADTMP)) {
 	    if (!PL_localizing && ckWARN(WARN_UNINITIALIZED))
@@ -2635,7 +2635,7 @@ Perl_sv_2nv(pTHX_ register SV *const sv)
     }
     else  {
 	if (isGV_with_GP(sv)) {
-	    glob_2number((GV *)sv);
+	    glob_2number(MUTABLE_GV(sv));
 	    return 0.0;
 	}
 
@@ -2978,7 +2978,7 @@ Perl_sv_2pv_flags(pTHX_ register SV *const sv, STRLEN *const lp, const I32 flags
     }
     else {
 	if (isGV_with_GP(sv))
-	    return glob_2pv((GV *)sv, lp);
+	    return glob_2pv(MUTABLE_GV(sv), lp);
 
 	if (lp)
 	    *lp = 0;
@@ -3403,17 +3403,17 @@ S_glob_assign_glob(pTHX_ SV *const dstr, SV *const sstr, const int dtype)
 	GvSTASH(dstr) = GvSTASH(sstr);
 	if (GvSTASH(dstr))
 	    Perl_sv_add_backref(aTHX_ MUTABLE_SV(GvSTASH(dstr)), dstr);
-	gv_name_set((GV *)dstr, name, len, GV_ADD);
+	gv_name_set(MUTABLE_GV(dstr), name, len, GV_ADD);
 	SvFAKE_on(dstr);	/* can coerce to non-glob */
     }
 
 #ifdef GV_UNIQUE_CHECK
-    if (GvUNIQUE((GV*)dstr)) {
+    if (GvUNIQUE((const GV *)dstr)) {
 	Perl_croak(aTHX_ PL_no_modify);
     }
 #endif
 
-    if(GvGP((GV*)sstr)) {
+    if(GvGP(MUTABLE_GV(sstr))) {
         /* If source has method cache entry, clear it */
         if(GvCVGEN(sstr)) {
             SvREFCNT_dec(GvCV(sstr));
@@ -3422,20 +3422,20 @@ S_glob_assign_glob(pTHX_ SV *const dstr, SV *const sstr, const int dtype)
         }
         /* If source has a real method, then a method is
            going to change */
-        else if(GvCV((GV*)sstr)) {
+        else if(GvCV((const GV *)sstr)) {
             mro_changes = 1;
         }
     }
 
     /* If dest already had a real method, that's a change as well */
-    if(!mro_changes && GvGP((GV*)dstr) && GvCVu((GV*)dstr)) {
+    if(!mro_changes && GvGP(MUTABLE_GV(dstr)) && GvCVu((const GV *)dstr)) {
         mro_changes = 1;
     }
 
-    if(strEQ(GvNAME((GV*)dstr),"ISA"))
+    if(strEQ(GvNAME((const GV *)dstr),"ISA"))
         mro_changes = 2;
 
-    gp_free((GV*)dstr);
+    gp_free(MUTABLE_GV(dstr));
     isGV_with_GP_off(dstr);
     (void)SvOK_off(dstr);
     isGV_with_GP_on(dstr);
@@ -3467,7 +3467,7 @@ S_glob_assign_ref(pTHX_ SV *const dstr, SV *const sstr)
     PERL_ARGS_ASSERT_GLOB_ASSIGN_REF;
 
 #ifdef GV_UNIQUE_CHECK
-    if (GvUNIQUE((GV*)dstr)) {
+    if (GvUNIQUE((const GV *)dstr)) {
 	Perl_croak(aTHX_ PL_no_modify);
     }
 #endif
@@ -3475,7 +3475,7 @@ S_glob_assign_ref(pTHX_ SV *const dstr, SV *const sstr)
     if (intro) {
 	GvINTRO_off(dstr);	/* one-shot flag */
 	GvLINE(dstr) = CopLINE(PL_curcop);
-	GvEGV(dstr) = (GV*)dstr;
+	GvEGV(dstr) = MUTABLE_GV(dstr);
     }
     GvMULTI_on(dstr);
     switch (stype) {
@@ -3516,7 +3516,7 @@ S_glob_assign_ref(pTHX_ SV *const dstr, SV *const sstr)
 	if (stype == SVt_PVCV && (*location != sref || GvCVGEN(dstr))) {
 	    CV* const cv = MUTABLE_CV(*location);
 	    if (cv) {
-		if (!GvCVGEN((GV*)dstr) &&
+		if (!GvCVGEN((const GV *)dstr) &&
 		    (CvROOT(cv) || CvXSUB(cv)))
 		    {
 			/* Redefining a sub - warning is mandatory if
@@ -3543,12 +3543,12 @@ S_glob_assign_ref(pTHX_ SV *const dstr, SV *const sstr)
 					(CvCONST(cv)
 					 ? "Constant subroutine %s::%s redefined"
 					 : "Subroutine %s::%s redefined"),
-					HvNAME_get(GvSTASH((GV*)dstr)),
-					GvENAME((GV*)dstr));
+					HvNAME_get(GvSTASH((const GV *)dstr)),
+					GvENAME(MUTABLE_GV(dstr)));
 			}
 		    }
 		if (!intro)
-		    cv_ckproto_len(cv, (GV*)dstr,
+		    cv_ckproto_len(cv, (const GV *)dstr,
 				   SvPOK(sref) ? SvPVX_const(sref) : NULL,
 				   SvPOK(sref) ? SvCUR(sref) : 0);
 	    }
@@ -3798,7 +3798,7 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, register SV* sstr, const I32 flags)
 	    GV *gv = gv_fetchsv(sstr, GV_ADD, SVt_PVGV);
 	    if (dstr != (const SV *)gv) {
 		if (GvGP(dstr))
-		    gp_free((GV*)dstr);
+		    gp_free(MUTABLE_GV(dstr));
 		GvGP(dstr) = gp_ref(GvGP(gv));
 	    }
 	}
@@ -3987,7 +3987,7 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, register SV* sstr, const I32 flags)
 	    /* FAKE globs can get coerced, so need to turn this off
 	       temporarily if it is on.  */
 	    SvFAKE_off(sstr);
-	    gv_efullname3(dstr, (GV *)sstr, "*");
+	    gv_efullname3(dstr, MUTABLE_GV(sstr), "*");
 	    SvFLAGS(sstr) |= wasfake;
 	}
 	else
@@ -5539,9 +5539,10 @@ Perl_sv_clear(pTHX_ register SV *const sv)
 	    SvREFCNT_dec(LvTARG(sv));
     case SVt_PVGV:
 	if (isGV_with_GP(sv)) {
-            if(GvCVu((GV*)sv) && (stash = GvSTASH((GV*)sv)) && HvNAME_get(stash))
+            if(GvCVu((const GV *)sv) && (stash = GvSTASH(MUTABLE_GV(sv)))
+	       && HvNAME_get(stash))
                 mro_method_changed_in(stash);
-	    gp_free((GV*)sv);
+	    gp_free(MUTABLE_GV(sv));
 	    if (GvNAME_HEK(sv))
 		unshare_hek(GvNAME_HEK(sv));
 	    /* If we're in a stash, we don't own a reference to it. However it does
@@ -5552,7 +5553,7 @@ Perl_sv_clear(pTHX_ register SV *const sv)
 	/* FIXME. There are probably more unreferenced pointers to SVs in the
 	   interpreter struct that we should check and tidy in a similar
 	   fashion to this:  */
-	if ((GV*)sv == PL_last_in_gv)
+	if ((const GV *)sv == PL_last_in_gv)
 	    PL_last_in_gv = NULL;
     case SVt_PVMG:
     case SVt_PVNV:
@@ -7836,7 +7837,7 @@ Perl_sv_reset(pTHX_ register const char *s, HV *const stash)
 
 		if (!todo[(U8)*HeKEY(entry)])
 		    continue;
-		gv = (GV*)HeVAL(entry);
+		gv = MUTABLE_GV(HeVAL(entry));
 		sv = GvSV(gv);
 		if (sv) {
 		    if (SvTHINKFIRST(sv)) {
@@ -7897,7 +7898,7 @@ Perl_sv_2io(pTHX_ SV *const sv)
 	break;
     case SVt_PVGV:
 	if (isGV_with_GP(sv)) {
-	    gv = (GV*)sv;
+	    gv = MUTABLE_GV(sv);
 	    io = GvIO(gv);
 	    if (!io)
 		Perl_croak(aTHX_ "Bad filehandle: %s", GvNAME(gv));
@@ -7957,7 +7958,7 @@ Perl_sv_2cv(pTHX_ SV *sv, HV **const st, GV **const gvp, const I32 lref)
 	return NULL;
     case SVt_PVGV:
 	if (isGV_with_GP(sv)) {
-	    gv = (GV*)sv;
+	    gv = MUTABLE_GV(sv);
 	    *gvp = gv;
 	    *st = GvESTASH(gv);
 	    goto fix_gv;
@@ -7978,13 +7979,13 @@ Perl_sv_2cv(pTHX_ SV *sv, HV **const st, GV **const gvp, const I32 lref)
 		return cv;
 	    }
 	    else if(isGV_with_GP(sv))
-		gv = (GV*)sv;
+		gv = MUTABLE_GV(sv);
 	    else
 		Perl_croak(aTHX_ "Not a subroutine reference");
 	}
 	else if (isGV_with_GP(sv)) {
 	    SvGETMAGIC(sv);
-	    gv = (GV*)sv;
+	    gv = MUTABLE_GV(sv);
 	}
 	else
 	    gv = gv_fetchsv(sv, lref, SVt_PVCV); /* Calls get magic */
@@ -8514,12 +8515,13 @@ S_sv_unglob(pTHX_ SV *const sv)
 
     assert(SvTYPE(sv) == SVt_PVGV);
     SvFAKE_off(sv);
-    gv_efullname3(temp, (GV *) sv, "*");
+    gv_efullname3(temp, MUTABLE_GV(sv), "*");
 
     if (GvGP(sv)) {
-        if(GvCVu((GV*)sv) && (stash = GvSTASH((GV*)sv)) && HvNAME_get(stash))
+        if(GvCVu((const GV *)sv) && (stash = GvSTASH(MUTABLE_GV(sv)))
+	   && HvNAME_get(stash))
             mro_method_changed_in(stash);
-	gp_free((GV*)sv);
+	gp_free(MUTABLE_GV(sv));
     }
     if (GvSTASH(sv)) {
 	sv_del_backref(MUTABLE_SV(GvSTASH(sv)), sv);
@@ -10096,8 +10098,8 @@ ptr_table_* functions.
 #define cv_dup_inc(s,t)	MUTABLE_CV(SvREFCNT_inc(sv_dup((const SV *)s,t)))
 #define io_dup(s,t)	MUTABLE_IO(sv_dup((const SV *)s,t))
 #define io_dup_inc(s,t)	MUTABLE_IO(SvREFCNT_inc(sv_dup((const SV *)s,t)))
-#define gv_dup(s,t)	(GV*)sv_dup((const SV *)s,t)
-#define gv_dup_inc(s,t)	(GV*)SvREFCNT_inc(sv_dup((const SV *)s,t))
+#define gv_dup(s,t)	MUTABLE_GV(sv_dup((const SV *)s,t))
+#define gv_dup_inc(s,t)	MUTABLE_GV(SvREFCNT_inc(sv_dup((const SV *)s,t)))
 #define SAVEPV(p)	((p) ? savepv(p) : NULL)
 #define SAVEPVN(p,n)	((p) ? savepvn(p,n) : NULL)
 
@@ -10661,7 +10663,7 @@ Perl_sv_dup(pTHX_ const SV *const sstr, CLONE_PARAMS *const param)
 		break;
 
 	    case SVt_PVGV:
-		if (GvUNIQUE((GV*)sstr)) {
+		if (GvUNIQUE((const GV *)sstr)) {
 		    NOOP;   /* Do sharing here, and fall through */
 		}
 	    case SVt_PVIO:
@@ -10965,7 +10967,8 @@ Perl_cx_dup(pTHX_ PERL_CONTEXT *cxs, I32 ix, I32 max, CLONE_PARAMS* param)
 						ncx->blk_loop.oldcomppad);
 		} else {
 		    ncx->blk_loop.oldcomppad
-			= (PAD*)gv_dup((GV*)ncx->blk_loop.oldcomppad, param);
+			= (PAD*)gv_dup((const GV *)ncx->blk_loop.oldcomppad,
+				       param);
 		}
 		break;
 	    case CXt_FORMAT:
@@ -11189,7 +11192,7 @@ Perl_ss_dup(pTHX_ PerlInterpreter *proto_perl, CLONE_PARAMS* param)
 	    gp = (GP*)POPPTR(ss,ix);
 	    TOPPTR(nss,ix) = gp = gp_dup(gp, param);
 	    (void)GpREFCNT_inc(gp);
-	    gv = (GV*)POPPTR(ss,ix);
+	    gv = (const GV *)POPPTR(ss,ix);
 	    TOPPTR(nss,ix) = gv_dup_inc(gv, param);
             break;
 	case SAVEt_FREEOP:
diff --git a/universal.c b/universal.c
index 6ba4439990..06dde0ccc2 100644
--- a/universal.c
+++ b/universal.c
@@ -949,11 +949,11 @@ XS(XS_PerlIO_get_layers)
 	}
 
 	sv = POPs;
-	gv = (GV*)sv;
+	gv = MUTABLE_GV(sv);
 
 	if (!isGV(sv)) {
 	     if (SvROK(sv) && isGV(SvRV(sv)))
-		  gv = (GV*)SvRV(sv);
+		  gv = MUTABLE_GV(SvRV(sv));
 	     else if (SvPOKp(sv))
 		  gv = gv_fetchsv(sv, 0, SVt_PVIO);
 	}
diff --git a/util.c b/util.c
index 3b31ffc9e9..70f81e7717 100644
--- a/util.c
+++ b/util.c
@@ -6005,7 +6005,8 @@ Perl_get_db_sub(pTHX_ SV **svp, CV *cv)
 	if ( svp && ((CvFLAGS(cv) & (CVf_ANON | CVf_CLONED))
 	     || strEQ(GvNAME(gv), "END")
 	     || ((GvCV(gv) != cv) && /* Could be imported, and old sub redefined. */
-		 !( (SvTYPE(*svp) == SVt_PVGV) && (GvCV((GV*)*svp) == cv) )))) {
+		 !( (SvTYPE(*svp) == SVt_PVGV)
+		    && (GvCV((const GV *)*svp) == cv) )))) {
 	    /* Use GV from the stack as a fallback. */
 	    /* GV is potentially non-unique, or contain different CV. */
 	    SV * const tmp = newRV(MUTABLE_SV(cv));
diff --git a/xsutils.c b/xsutils.c
index e5c3dd8dbf..4d560ec4ce 100644
--- a/xsutils.c
+++ b/xsutils.c
@@ -260,8 +260,8 @@ usage:
 		stash = CvSTASH(sv);
 	    break;
 	case SVt_PVGV:
-	    if (isGV_with_GP(sv) && GvGP(sv) && GvESTASH((GV*)sv))
-		stash = GvESTASH((GV*)sv);
+	    if (isGV_with_GP(sv) && GvGP(sv) && GvESTASH(MUTABLE_GV(sv)))
+		stash = GvESTASH(MUTABLE_GV(sv));
 	    break;
 	default:
 	    break;