fix various compiler warnings from XS code

Trivial changes to fix warnings of types
* unclear precedence
* assignment as conditional
* signed/unsigned mixing
* unused parameter/variable
* value computed not used
* wrong argument type for a printf format
* variable may be used uninitialised (due to unhandled switch case)

13 files changed, 96 insertions, 48 deletions

diff --git a/ext/B/B.xs b/ext/B/B.xs
index b439236abb..c5d971ba89 100644
--- a/ext/B/B.xs
+++ b/ext/B/B.xs
@@ -258,7 +258,7 @@ make_sv_object(pTHX_ SV *sv)
     IV iv;
     dMY_CXT;
 
-    for (iv = 0; iv < sizeof(specialsv_list)/sizeof(SV*); iv++) {
+    for (iv = 0; iv < (IV)(sizeof(specialsv_list)/sizeof(SV*)); iv++) {
 	if (sv == specialsv_list[iv]) {
 	    type = "B::SPECIAL";
 	    break;
@@ -959,6 +959,9 @@ next(o)
 	    ret = sv_2mortal(newSVpv(*((char **)ptr), 0));
 	    break;
 #endif
+	default:
+	    croak("Illegal alias 0x%08x for B::*next", (unsigned)ix);
+
 	}
 	ST(0) = ret;
 	XSRETURN(1);
@@ -1516,6 +1519,8 @@ IVX(sv)
 	case (U8)(sv_U16p >> 16):
 	    ret = sv_2mortal(newSVuv(*((U16 *)ptr)));
 	    break;
+	default:
+	    croak("Illegal alias 0x%08x for B::*IVX", (unsigned)ix);
 	}
 	ST(0) = ret;
 	XSRETURN(1);
@@ -1808,6 +1813,8 @@ SV(gv)
 	case (U8)(line_tp >> 16):
 	    ret = sv_2mortal(newSVuv(*((line_t *)ptr)));
 	    break;
+	default:
+	    croak("Illegal alias 0x%08x for B::*SV", (unsigned)ix);
 	}
 	ST(0) = ret;
 	XSRETURN(1);
diff --git a/ext/Devel-Peek/Peek.xs b/ext/Devel-Peek/Peek.xs
index d555ab7d08..3dcba4780e 100644
--- a/ext/Devel-Peek/Peek.xs
+++ b/ext/Devel-Peek/Peek.xs
@@ -294,18 +294,25 @@ mstats2hash(SV *sv, SV *rv, int level)
 static void
 fill_mstats(SV *sv, int level)
 {
+    PERL_UNUSED_ARG(sv);
+    PERL_UNUSED_ARG(level);
     croak("Cannot report mstats without Perl malloc");
 }
 
 static void
 mstats_fillhash(SV *sv, int level)
 {
+    PERL_UNUSED_ARG(sv);
+    PERL_UNUSED_ARG(level);
     croak("Cannot report mstats without Perl malloc");
 }
 
 static void
 mstats2hash(SV *sv, SV *rv, int level)
 {
+    PERL_UNUSED_ARG(sv);
+    PERL_UNUSED_ARG(rv);
+    PERL_UNUSED_ARG(level);
     croak("Cannot report mstats without Perl malloc");
 }
 #endif	/* defined(MYMALLOC) */ 
diff --git a/ext/Fcntl/Fcntl.xs b/ext/Fcntl/Fcntl.xs
index d650994df3..36703a8545 100644
--- a/ext/Fcntl/Fcntl.xs
+++ b/ext/Fcntl/Fcntl.xs
@@ -53,7 +53,7 @@ XS_Fcntl_S_ISREG(pTHX_ CV* cv)
 	mode = &PL_sv_undef;
 	EXTEND(SP, 1);
     }
-    PUSHs(((SvUV(mode) & S_IFMT) == ix) ? &PL_sv_yes : &PL_sv_no);
+    PUSHs(((SvUV(mode) & S_IFMT) == (UV)ix) ? &PL_sv_yes : &PL_sv_no);
     PUTBACK;
 }
 
diff --git a/ext/File-Glob/Glob.xs b/ext/File-Glob/Glob.xs
index d4b453c39d..56f76eba8a 100644
--- a/ext/File-Glob/Glob.xs
+++ b/ext/File-Glob/Glob.xs
@@ -21,6 +21,7 @@ START_MY_CXT
 #else
 static int
 errfunc(const char *foo, int bar) {
+  PERL_UNUSED_ARG(foo);
   return !(bar == EACCES || bar == ENOENT || bar == ENOTDIR);
 }
 #endif
diff --git a/ext/Hash-Util-FieldHash/FieldHash.xs b/ext/Hash-Util-FieldHash/FieldHash.xs
index 2c9664660b..c7df46bcb5 100644
--- a/ext/Hash-Util-FieldHash/FieldHash.xs
+++ b/ext/Hash-Util-FieldHash/FieldHash.xs
@@ -116,6 +116,7 @@ AV* HUF_get_trigger_content(SV* trigger) {
  * the uf_set field of the uvar magic of a trigger.
  */
 I32 HUF_destroy_obj(pTHX_ IV index, SV* trigger) {
+    PERL_UNUSED_ARG(index);
     /* Do nothing if the weakref wasn't undef'd.  Also don't bother
      * during global destruction.  (MY_CXT.ob_reg is sometimes funny there) */
     if (!SvROK(trigger) && (!PL_in_clean_all)) {
@@ -125,15 +126,15 @@ I32 HUF_destroy_obj(pTHX_ IV index, SV* trigger) {
         HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
         HE* ent;
         hv_iterinit(field_tab);
-        while (ent = hv_iternext(field_tab)) {
+        while ((ent = hv_iternext(field_tab))) {
             SV* field_ref = HeVAL(ent);
             SV* field = SvRV(field_ref);
-            hv_delete_ent((HV*)field, ob_id, 0, 0);
+            (void) hv_delete_ent((HV*)field, ob_id, 0, 0);
         }
         /* make it safe in case we must run in global clenaup, after all */
         if (PL_in_clean_all)
             HUF_global(HUF_RESET); /* shoudn't be needed */
-        hv_delete_ent(MY_CXT.ob_reg, ob_id, 0, 0);
+        (void) hv_delete_ent(MY_CXT.ob_reg, ob_id, 0, 0);
     }
     return 0;
 }
@@ -154,7 +155,7 @@ SV* HUF_new_trigger(SV* obj, SV* ob_id) {
     av_store(cont, 0, SvREFCNT_inc(ob_id));
     av_store(cont, 1, (SV*)newHV());
     HUF_add_uvar_magic(trigger, NULL, &HUF_destroy_obj, 0, (SV*)cont);
-    hv_store_ent(MY_CXT.ob_reg, ob_id, trigger, 0);
+    (void) hv_store_ent(MY_CXT.ob_reg, ob_id, trigger, 0);
     return trigger;
 }
 
@@ -162,7 +163,7 @@ SV* HUF_new_trigger(SV* obj, SV* ob_id) {
 SV* HUF_ask_trigger(SV* ob_id) {
     dMY_CXT;
     HE* ent;
-    if (ent = hv_fetch_ent(MY_CXT.ob_reg, ob_id, 0, 0))
+    if ((ent = hv_fetch_ent(MY_CXT.ob_reg, ob_id, 0, 0)))
         return HeVAL(ent);
     return NULL;
 }
@@ -190,7 +191,7 @@ void HUF_mark_field(SV* trigger, SV* field) {
     HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
     SV* field_ref = newRV_inc(field);
     UV field_addr = PTR2UV(field);
-    hv_store(field_tab, (char *)&field_addr, sizeof(field_addr), field_ref, 0);
+    (void) hv_store(field_tab, (char *)&field_addr, sizeof(field_addr), field_ref, 0);
 }
 
 /* Determine, from the value of action, whether this call may create a new
@@ -213,7 +214,7 @@ I32 HUF_watch_key_safe(pTHX_ IV action, SV* field) {
         } else if (HUF_WOULD_CREATE_KEY(action)) { /* string key */
             /* registered as object id? */
             SV* trigger;
-            if ( trigger = HUF_ask_trigger(keysv))
+            if (( trigger = HUF_ask_trigger(keysv)))
                 HUF_mark_field( trigger, field);
         }
     } else {
@@ -225,6 +226,7 @@ I32 HUF_watch_key_safe(pTHX_ IV action, SV* field) {
 I32 HUF_watch_key_id(pTHX_ IV action, SV* field) {
     MAGIC* mg = mg_find(field, PERL_MAGIC_uvar);
     SV* keysv;
+    PERL_UNUSED_ARG(action);
     if (mg && (keysv = mg->mg_obj)) {
         if (SvROK(keysv)) /* ref key */
             mg->mg_obj = HUF_obj_id(keysv); /* key replacement */
@@ -282,16 +284,16 @@ void HUF_fix_trigger(SV* trigger, SV* new_id) {
     HE* ent;
     SV* old_id = *av_fetch(cont, 0, 0);
     hv_iterinit(field_tab);
-    while (ent = hv_iternext(field_tab)) {
+    while ((ent = hv_iternext(field_tab))) {
         SV* field_ref = HeVAL(ent);
         HV* field = (HV*)SvRV(field_ref);
         UV field_addr = PTR2UV(field);
         SV* val;
         /* recreate field tab entry */
-        hv_store(new_tab, (char *)&field_addr, sizeof(field_addr), SvREFCNT_inc(field_ref), 0);
+        (void) hv_store(new_tab, (char *)&field_addr, sizeof(field_addr), SvREFCNT_inc(field_ref), 0);
         /* recreate field entry, if any */
-        if (val = hv_delete_ent(field, old_id, 0, 0))
-            hv_store_ent(field, new_id, SvREFCNT_inc(val), 0);
+        if ((val = hv_delete_ent(field, old_id, 0, 0)))
+            (void) hv_store_ent(field, new_id, SvREFCNT_inc(val), 0);
     }
     /* update the trigger */
     av_store(cont, 0, SvREFCNT_inc(new_id));
@@ -307,7 +309,7 @@ void HUF_fix_objects(void) {
     HE* ent;
     AV* oblist = (AV*)sv_2mortal((SV*)newAV());
     hv_iterinit(MY_CXT.ob_reg);
-    while(ent = hv_iternext(MY_CXT.ob_reg))
+    while((ent = hv_iternext(MY_CXT.ob_reg)))
         av_push(oblist, SvREFCNT_inc(hv_iterkeysv(ent)));
     len = av_len(oblist);
     for (i = 0; i <= len; ++i) {
@@ -328,7 +330,7 @@ void HUF_fix_objects(void) {
         }
 
         HUF_fix_trigger(trigger, new_id);
-        hv_store_ent(MY_CXT.ob_reg, new_id, SvREFCNT_inc(trigger), 0);
+        (void) hv_store_ent(MY_CXT.ob_reg, new_id, SvREFCNT_inc(trigger), 0);
     }
 }
 
@@ -336,6 +338,8 @@ void HUF_fix_objects(void) {
 
 static SV* counter;
 I32 HUF_inc_var(pTHX_ IV index, SV* which) {
+    PERL_UNUSED_ARG(index);
+    PERL_UNUSED_ARG(which);
     sv_setiv(counter, 1 + SvIV(counter));
     return 0;
 }
@@ -435,7 +439,7 @@ PPCODE:
             HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
             HE* ent;
             hv_iterinit(field_tab);
-            while (ent = hv_iternext(field_tab)) {
+            while ((ent = hv_iternext(field_tab))) {
                 HV* field = (HV*)SvRV(HeVAL(ent));
                 if (hv_exists_ent(field, ob_id, 0))
                     XPUSHs(sv_2mortal(newRV_inc((SV*)field)));
diff --git a/ext/Opcode/Opcode.xs b/ext/Opcode/Opcode.xs
index 4d6df48ab7..1e5f8c22db 100644
--- a/ext/Opcode/Opcode.xs
+++ b/ext/Opcode/Opcode.xs
@@ -52,7 +52,7 @@ op_names_init(pTHX)
     for(i=0; i < PL_maxo; ++i) {
 	SV * const sv = newSViv(i);
 	SvREADONLY_on(sv);
-	hv_store(op_named_bits, op_names[i], strlen(op_names[i]), sv, 0);
+	(void) hv_store(op_named_bits, op_names[i], strlen(op_names[i]), sv, 0);
     }
 
     put_op_bitspec(aTHX_ STR_WITH_LEN(":none"), sv_2mortal(new_opset(aTHX_ Nullsv)));
@@ -264,7 +264,7 @@ PPCODE:
     if (strNE(HvNAME_get(hv),"main")) {
         /* make it think it's in main:: */
 	hv_name_set(hv, "main", 4, 0);
-        hv_store(hv,"_",1,(SV *)PL_defgv,0);  /* connect _ to global */
+        (void) hv_store(hv,"_",1,(SV *)PL_defgv,0);  /* connect _ to global */
         SvREFCNT_inc((SV *)PL_defgv);  /* want to keep _ around! */
     }
     LEAVE;
diff --git a/ext/POSIX/POSIX.xs b/ext/POSIX/POSIX.xs
index 2b9af9501a..92ab1bcded 100644
--- a/ext/POSIX/POSIX.xs
+++ b/ext/POSIX/POSIX.xs
@@ -936,7 +936,7 @@ WEXITSTATUS(status)
 #endif
 	    break;
 	default:
-	    Perl_croak(aTHX_ "Illegal alias %d for POSIX::W*", ix);
+	    Perl_croak(aTHX_ "Illegal alias %d for POSIX::W*", (int)ix);
 	}
     OUTPUT:
 	RETVAL
@@ -1118,65 +1118,65 @@ localeconv()
 	if ((lcbuf = localeconv())) {
 	    /* the strings */
 	    if (lcbuf->decimal_point && *lcbuf->decimal_point)
-		hv_store(RETVAL, "decimal_point", 13,
+		(void) hv_store(RETVAL, "decimal_point", 13,
 		    newSVpv(lcbuf->decimal_point, 0), 0);
 	    if (lcbuf->thousands_sep && *lcbuf->thousands_sep)
-		hv_store(RETVAL, "thousands_sep", 13,
+		(void) hv_store(RETVAL, "thousands_sep", 13,
 		    newSVpv(lcbuf->thousands_sep, 0), 0);
 #ifndef NO_LOCALECONV_GROUPING
 	    if (lcbuf->grouping && *lcbuf->grouping)
-		hv_store(RETVAL, "grouping", 8,
+		(void) hv_store(RETVAL, "grouping", 8,
 		    newSVpv(lcbuf->grouping, 0), 0);
 #endif
 	    if (lcbuf->int_curr_symbol && *lcbuf->int_curr_symbol)
-		hv_store(RETVAL, "int_curr_symbol", 15,
+		(void) hv_store(RETVAL, "int_curr_symbol", 15,
 		    newSVpv(lcbuf->int_curr_symbol, 0), 0);
 	    if (lcbuf->currency_symbol && *lcbuf->currency_symbol)
-		hv_store(RETVAL, "currency_symbol", 15,
+		(void) hv_store(RETVAL, "currency_symbol", 15,
 		    newSVpv(lcbuf->currency_symbol, 0), 0);
 	    if (lcbuf->mon_decimal_point && *lcbuf->mon_decimal_point)
-		hv_store(RETVAL, "mon_decimal_point", 17,
+		(void) hv_store(RETVAL, "mon_decimal_point", 17,
 		    newSVpv(lcbuf->mon_decimal_point, 0), 0);
 #ifndef NO_LOCALECONV_MON_THOUSANDS_SEP
 	    if (lcbuf->mon_thousands_sep && *lcbuf->mon_thousands_sep)
-		hv_store(RETVAL, "mon_thousands_sep", 17,
+		(void) hv_store(RETVAL, "mon_thousands_sep", 17,
 		    newSVpv(lcbuf->mon_thousands_sep, 0), 0);
 #endif
 #ifndef NO_LOCALECONV_MON_GROUPING
 	    if (lcbuf->mon_grouping && *lcbuf->mon_grouping)
-		hv_store(RETVAL, "mon_grouping", 12,
+		(void) hv_store(RETVAL, "mon_grouping", 12,
 		    newSVpv(lcbuf->mon_grouping, 0), 0);
 #endif
 	    if (lcbuf->positive_sign && *lcbuf->positive_sign)
-		hv_store(RETVAL, "positive_sign", 13,
+		(void) hv_store(RETVAL, "positive_sign", 13,
 		    newSVpv(lcbuf->positive_sign, 0), 0);
 	    if (lcbuf->negative_sign && *lcbuf->negative_sign)
-		hv_store(RETVAL, "negative_sign", 13,
+		(void) hv_store(RETVAL, "negative_sign", 13,
 		    newSVpv(lcbuf->negative_sign, 0), 0);
 	    /* the integers */
 	    if (lcbuf->int_frac_digits != CHAR_MAX)
-		hv_store(RETVAL, "int_frac_digits", 15,
+		(void) hv_store(RETVAL, "int_frac_digits", 15,
 		    newSViv(lcbuf->int_frac_digits), 0);
 	    if (lcbuf->frac_digits != CHAR_MAX)
-		hv_store(RETVAL, "frac_digits", 11,
+		(void) hv_store(RETVAL, "frac_digits", 11,
 		    newSViv(lcbuf->frac_digits), 0);
 	    if (lcbuf->p_cs_precedes != CHAR_MAX)
-		hv_store(RETVAL, "p_cs_precedes", 13,
+		(void) hv_store(RETVAL, "p_cs_precedes", 13,
 		    newSViv(lcbuf->p_cs_precedes), 0);
 	    if (lcbuf->p_sep_by_space != CHAR_MAX)
-		hv_store(RETVAL, "p_sep_by_space", 14,
+		(void) hv_store(RETVAL, "p_sep_by_space", 14,
 		    newSViv(lcbuf->p_sep_by_space), 0);
 	    if (lcbuf->n_cs_precedes != CHAR_MAX)
-		hv_store(RETVAL, "n_cs_precedes", 13,
+		(void) hv_store(RETVAL, "n_cs_precedes", 13,
 		    newSViv(lcbuf->n_cs_precedes), 0);
 	    if (lcbuf->n_sep_by_space != CHAR_MAX)
-		hv_store(RETVAL, "n_sep_by_space", 14,
+		(void) hv_store(RETVAL, "n_sep_by_space", 14,
 		    newSViv(lcbuf->n_sep_by_space), 0);
 	    if (lcbuf->p_sign_posn != CHAR_MAX)
-		hv_store(RETVAL, "p_sign_posn", 11,
+		(void) hv_store(RETVAL, "p_sign_posn", 11,
 		    newSViv(lcbuf->p_sign_posn), 0);
 	    if (lcbuf->n_sign_posn != CHAR_MAX)
-		hv_store(RETVAL, "n_sign_posn", 11,
+		(void) hv_store(RETVAL, "n_sign_posn", 11,
 		    newSViv(lcbuf->n_sign_posn), 0);
 	}
 #else
diff --git a/ext/PerlIO-encoding/encoding.xs b/ext/PerlIO-encoding/encoding.xs
index 2d515b6540..e94555ce95 100644
--- a/ext/PerlIO-encoding/encoding.xs
+++ b/ext/PerlIO-encoding/encoding.xs
@@ -58,6 +58,8 @@ PerlIOEncode_getarg(pTHX_ PerlIO * f, CLONE_PARAMS * param, int flags)
 {
     PerlIOEncode *e = PerlIOSelf(f, PerlIOEncode);
     SV *sv = &PL_sv_undef;
+    PERL_UNUSED_ARG(param);
+    PERL_UNUSED_ARG(flags);
     if (e->enc) {
 	dSP;
 	/* Not 100% sure stack swap is right thing to do during dup ... */
diff --git a/ext/PerlIO-scalar/scalar.xs b/ext/PerlIO-scalar/scalar.xs
index 6fe551d34c..e081c17f50 100644
--- a/ext/PerlIO-scalar/scalar.xs
+++ b/ext/PerlIO-scalar/scalar.xs
@@ -84,6 +84,7 @@ PerlIOScalar_close(pTHX_ PerlIO * f)
 IV
 PerlIOScalar_fileno(pTHX_ PerlIO * f)
 {
+    PERL_UNUSED_ARG(f);
     return -1;
 }
 
@@ -156,7 +157,7 @@ PerlIOScalar_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 	got = len - (STRLEN)(s->posn);
 	if (got <= 0)
 	    return 0;
-	if (got > (STRLEN)count)
+	if ((STRLEN)got > (STRLEN)count)
 	    got = (STRLEN)count;
 	Copy(p + (STRLEN)(s->posn), vbuf, got, STDCHAR);
 	s->posn += (Off_t)got;
@@ -201,12 +202,14 @@ PerlIOScalar_write(pTHX_ PerlIO * f, const void *vbuf, Size_t count)
 IV
 PerlIOScalar_fill(pTHX_ PerlIO * f)
 {
+    PERL_UNUSED_ARG(f);
     return -1;
 }
 
 IV
 PerlIOScalar_flush(pTHX_ PerlIO * f)
 {
+    PERL_UNUSED_ARG(f);
     return 0;
 }
 
@@ -260,6 +263,7 @@ void
 PerlIOScalar_set_ptrcnt(pTHX_ PerlIO * f, STDCHAR * ptr, SSize_t cnt)
 {
     PerlIOScalar *s = PerlIOSelf(f, PerlIOScalar);
+    PERL_UNUSED_ARG(ptr);
     SvGETMAGIC(s->var);
     s->posn = SvCUR(s->var) - cnt;
 }
@@ -270,6 +274,9 @@ PerlIOScalar_open(pTHX_ PerlIO_funcs * self, PerlIO_list_t * layers, IV n,
 		  PerlIO * f, int narg, SV ** args)
 {
     SV *arg = (narg > 0) ? *args : PerlIOArg;
+    PERL_UNUSED_ARG(fd);
+    PERL_UNUSED_ARG(imode);
+    PERL_UNUSED_ARG(perm);
     if (SvROK(arg) || SvPOK(arg)) {
 	if (!f) {
 	    f = PerlIO_allocate(aTHX);
diff --git a/ext/PerlIO-via/via.xs b/ext/PerlIO-via/via.xs
index a811578ca2..56889bfef6 100644
--- a/ext/PerlIO-via/via.xs
+++ b/ext/PerlIO-via/via.xs
@@ -93,7 +93,7 @@ PerlIOVia_method(pTHX_ PerlIO * f, const char *method, CV ** save, int flags,
 		s->io = GvIOp(gv);
 		if (gv) {
 		    /* shamelessly stolen from IO::File's new_tmpfile() */
-		    hv_delete(GvSTASH(gv), GvNAME(gv), GvNAMELEN(gv), G_DISCARD);
+		    (void) hv_delete(GvSTASH(gv), GvNAME(gv), GvNAMELEN(gv), G_DISCARD);
 		}
 	    }
 	    IoIFP(s->io) = PerlIONext(f);
@@ -536,6 +536,7 @@ void
 PerlIOVia_set_ptrcnt(pTHX_ PerlIO * f, STDCHAR * ptr, SSize_t cnt)
 {
     PerlIOVia *s = PerlIOSelf(f, PerlIOVia);
+    PERL_UNUSED_ARG(ptr);
     s->cnt = cnt;
 }
 
@@ -577,6 +578,8 @@ SV *
 PerlIOVia_getarg(pTHX_ PerlIO * f, CLONE_PARAMS * param, int flags)
 {
     PerlIOVia *s = PerlIOSelf(f, PerlIOVia);
+    PERL_UNUSED_ARG(param);
+    PERL_UNUSED_ARG(flags);
     return PerlIOVia_method(aTHX_ f, MYMethod(GETARG), G_SCALAR, Nullsv);
 }
 
diff --git a/ext/SDBM_File/sdbm/pair.c b/ext/SDBM_File/sdbm/pair.c
index 42b130db19..993a361186 100644
--- a/ext/SDBM_File/sdbm/pair.c
+++ b/ext/SDBM_File/sdbm/pair.c
@@ -281,7 +281,7 @@ chkpage(char *pag)
 	register int off;
 	register short *ino = (short *) pag;
 
-	if ((n = ino[0]) < 0 || n > PBLKSIZ / sizeof(short))
+	if ((n = ino[0]) < 0 || n > (int)(PBLKSIZ / sizeof(short)))
 		return 0;
 
 	if (n > 0) {
diff --git a/ext/Socket/Socket.xs b/ext/Socket/Socket.xs
index ce6ec34d89..dcf6715727 100644
--- a/ext/Socket/Socket.xs
+++ b/ext/Socket/Socket.xs
@@ -385,7 +385,7 @@ unpack_sockaddr_un(sun_sv)
 		addr_len = (char *)&addr - (char *)&(addr.sun_path) + sockaddrlen;
 	} else {
 		for (addr_len = 0; addr.sun_path[addr_len]
-		     && addr_len < sizeof addr.sun_path; addr_len++);
+		     && addr_len < (int)sizeof(addr.sun_path); addr_len++);
 	}
 
 	ST(0) = newSVpvn_flags(addr.sun_path, addr_len, SVs_TEMP);
diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index 71551ee696..03bbc921f8 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -95,8 +95,8 @@ test_freeent(freeent_function *f) {
 #else
     /* Storing then deleting something should ensure that a hash entry is
        available.  */
-    hv_store(test_hash, "", 0, &PL_sv_yes, 0);
-    hv_delete(test_hash, "", 0, 0);
+    (void) hv_store(test_hash, "", 0, &PL_sv_yes, 0);
+    (void) hv_delete(test_hash, "", 0, 0);
 
     /* We need to "inline" new_he here as it's static, and the functions we
        test expect to be able to call del_HE on the HE  */
@@ -124,7 +124,7 @@ test_freeent(freeent_function *f) {
     i = 0;
     do {
 	mPUSHu(results[i]);
-    } while (++i < sizeof(results)/sizeof(results[0]));
+    } while (++i < (int)(sizeof(results)/sizeof(results[0])));
 
     /* Goodbye to our extra reference.  */
     SvREFCNT_dec(test_scalar);
@@ -135,6 +135,7 @@ static I32
 bitflip_key(pTHX_ IV action, SV *field) {
     MAGIC *mg = mg_find(field, PERL_MAGIC_uvar);
     SV *keysv;
+    PERL_UNUSED_ARG(action);
     if (mg && (keysv = mg->mg_obj)) {
 	STRLEN len;
 	const char *p = SvPV(keysv, len);
@@ -170,6 +171,7 @@ static I32
 rot13_key(pTHX_ IV action, SV *field) {
     MAGIC *mg = mg_find(field, PERL_MAGIC_uvar);
     SV *keysv;
+    PERL_UNUSED_ARG(action);
     if (mg && (keysv = mg->mg_obj)) {
 	STRLEN len;
 	const char *p = SvPV(keysv, len);
@@ -252,6 +254,8 @@ rot13_key(pTHX_ IV action, SV *field) {
 
 STATIC I32
 rmagical_a_dummy(pTHX_ IV idx, SV *sv) {
+    PERL_UNUSED_ARG(idx);
+    PERL_UNUSED_ARG(sv);
     return 0;
 }
 
@@ -263,6 +267,7 @@ blockhook_csc_start(pTHX_ int full)
     dMY_CXT;
     AV *const cur = GvAV(MY_CXT.cscgv);
 
+    PERL_UNUSED_ARG(full);
     SAVEGENERICSV(GvAV(MY_CXT.cscgv));
 
     if (cur) {
@@ -282,6 +287,7 @@ blockhook_csc_pre_end(pTHX_ OP **o)
 {
     dMY_CXT;
 
+    PERL_UNUSED_ARG(o);
     /* if we hit the end of a scope we missed the start of, we need to
      * unconditionally clear @CSC */
     if (GvAV(MY_CXT.cscgv) == MY_CXT.cscav && MY_CXT.cscav) {
@@ -309,6 +315,7 @@ blockhook_test_pre_end(pTHX_ OP **o)
 {
     dMY_CXT;
 
+    PERL_UNUSED_ARG(o);
     if (MY_CXT.bhk_record)
         av_push(MY_CXT.bhkav, newSVpvs("pre_end"));
 }
@@ -318,6 +325,7 @@ blockhook_test_post_end(pTHX_ OP **o)
 {
     dMY_CXT;
 
+    PERL_UNUSED_ARG(o);
     if (MY_CXT.bhk_record)
         av_push(MY_CXT.bhkav, newSVpvs("post_end"));
 }
@@ -381,6 +389,8 @@ my_rpeep (pTHX_ OP *o)
 STATIC OP *
 THX_ck_entersub_args_lists(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
 {
+    PERL_UNUSED_ARG(namegv);
+    PERL_UNUSED_ARG(ckobj);
     return ck_entersub_args_list(entersubop);
 }
 
@@ -388,6 +398,8 @@ STATIC OP *
 THX_ck_entersub_args_scalars(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
 {
     OP *aop = cUNOPx(entersubop)->op_first;
+    PERL_UNUSED_ARG(namegv);
+    PERL_UNUSED_ARG(ckobj);
     if (!aop->op_sibling)
 	aop = cUNOPx(aop)->op_first;
     for (aop = aop->op_sibling; aop->op_sibling; aop = aop->op_sibling) {
@@ -401,6 +413,8 @@ THX_ck_entersub_multi_sum(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
 {
     OP *sumop = NULL;
     OP *pushop = cUNOPx(entersubop)->op_first;
+    PERL_UNUSED_ARG(namegv);
+    PERL_UNUSED_ARG(ckobj);
     if (!pushop->op_sibling)
 	pushop = cUNOPx(pushop)->op_first;
     while (1) {
@@ -561,7 +575,7 @@ THX_ck_entersub_establish_cleanup(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
 STATIC OP *
 THX_ck_entersub_postinc(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
 {
-    OP *pushop, *argop, *estop;
+    OP *pushop, *argop;
     ck_entersub_args_proto(entersubop, namegv, ckobj);
     pushop = cUNOPx(entersubop)->op_first;
     if(!pushop->op_sibling) pushop = cUNOPx(pushop)->op_first;
@@ -952,7 +966,7 @@ bytes_cmp_utf8(bytes, utf8)
 
 MODULE = XS::APItest:Overload	PACKAGE = XS::APItest::Overload
 
-SV *
+void
 amagic_deref_call(sv, what)
 	SV *sv
 	int what
@@ -963,7 +977,7 @@ amagic_deref_call(sv, what)
 # I'd certainly like to discourage the use of this macro, given that we now
 # have amagic_deref_call
 
-SV *
+void
 tryAMAGICunDEREF_var(sv, what)
 	SV *sv
 	int what
@@ -1463,7 +1477,7 @@ xop_build_optree ()
 
         av_push(MY_CXT.xop_record, newSVpvf("NAME:%s", OP_NAME((OP*)unop)));
         av_push(MY_CXT.xop_record, newSVpvf("DESC:%s", OP_DESC((OP*)unop)));
-        av_push(MY_CXT.xop_record, newSVpvf("CLASS:%d", OP_CLASS((OP*)unop)));
+        av_push(MY_CXT.xop_record, newSVpvf("CLASS:%d", (int)OP_CLASS((OP*)unop)));
 
         PL_rpeepp(aTHX_ kid);
 
@@ -1512,6 +1526,7 @@ void
 CLONE(...)
     CODE:
     MY_CXT_CLONE;
+    PERL_UNUSED_VAR(items);
     MY_CXT.sv = newSVpv("initial_clone",0);
     MY_CXT.cscgv = gv_fetchpvs("XS::APItest::COMPILE_SCOPE_CONTAINER",
         GV_ADDMULTI, SVt_PVAV);
@@ -2652,6 +2667,7 @@ void
 establish_cleanup(...)
 PROTOTYPE: $
 CODE:
+    PERL_UNUSED_VAR(items);
     croak("establish_cleanup called as a function");
 
 BOOT:
@@ -2664,6 +2680,7 @@ void
 postinc(...)
 PROTOTYPE: $
 CODE:
+    PERL_UNUSED_VAR(items);
     croak("postinc called as a function");
 
 BOOT: