Insert asserts to paths suspected by Coverity.

Coverity suspects paths like this:

(1)

  p = foo();
  if (!p) p = bar();
  baz(p->q);

since it cannot prove that p is always non-NULL at the dereference.

(2) Or simply something like:

  mg = mg_find(...);
  foo(mg->blah);

Since mg_find() can fail returning NULL.

Adding assert() calls before the dereferences.  Testing with -DDEBUGGING.
Hopefully there are regular smokes doing the same.

[perl #121894]

Fix for Coverity perl5 CIDs 28950,28952..28955,28964,28967,28970..28795,49921:
CID ...: Dereference after null check (FORWARD_NULL)
var_deref_op: Dereferencing null pointer p->q

(TODO: Coverity perl5 CIDs 28962,28968,28969: the same issue, but would
conflict with already in-flight changes, prepare catch-up patch later.)
---
 dist/Data-Dumper/Dumper.xs | 1 +
 dump.c                     | 1 +
 ext/Devel-Peek/Peek.xs     | 1 +
 ext/XS-APItest/APItest.xs  | 1 +
 mg.c                       | 2 ++
 mro.c                      | 4 +++-
 op.c                       | 4 ++++
 perlio.c                   | 1 +
 pp_hot.c                   | 5 +++--
 regcomp.c                  | 3 +++
 regexec.c                  | 5 ++++-
 universal.c                | 2 +-
 util.c                     | 4 +++-
 13 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/dist/Data-Dumper/Dumper.xs b/dist/Data-Dumper/Dumper.xs
index 12c4ebd..23e0cf4 100644
--- a/dist/Data-Dumper/Dumper.xs
+++ b/dist/Data-Dumper/Dumper.xs
@@ -641,6 +641,7 @@ DD_dump(pTHX_ SV *val, const char *name, STRLEN namelen, SV *retval, HV *seenhv,
 	    else {
 	      sv_pattern = val;
 	    }
+	    assert(sv_pattern);
 	    rval = SvPV(sv_pattern, rlen);
 	    rend = rval+rlen;
 	    slash = rval;
diff --git a/dump.c b/dump.c
index 59be3e0..c2d72fd 100644
--- a/dump.c
+++ b/dump.c
@@ -471,6 +471,7 @@ Perl_sv_peek(pTHX_ SV *sv)
   finish:
     while (unref--)
 	sv_catpv(t, ")");
+    /* XXX when is sv ever NULL? */
     if (TAINTING_get && SvTAINTED(sv))
 	sv_catpv(t, " [tainted]");
     return SvPV_nolen(t);
diff --git a/ext/Devel-Peek/Peek.xs b/ext/Devel-Peek/Peek.xs
index 679efa5..b20fa94 100644
--- a/ext/Devel-Peek/Peek.xs
+++ b/ext/Devel-Peek/Peek.xs
@@ -450,6 +450,7 @@ PPCODE:
 BOOT:
 {
     CV * const cv = get_cvn_flags("Devel::Peek::Dump", 17, 0);
+    assert(cv);
     cv_set_call_checker(cv, S_ck_dump, (SV *)cv);

     XopENTRY_set(&my_xop, xop_name, "Dump");
diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index a51924d..18ba381 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -2096,6 +2096,7 @@ newCONSTSUB(stash, name, flags, sv)
                break;
         }
         EXTEND(SP, 2);
+        assert(mycv);
         PUSHs( CvCONST(mycv) ? &PL_sv_yes : &PL_sv_no );
         PUSHs((SV*)CvGV(mycv));

diff --git a/mg.c b/mg.c
index 76912bd..7f3339a 100644
--- a/mg.c
+++ b/mg.c
@@ -1675,6 +1675,7 @@ Perl_magic_clearisa(pTHX_ SV *sv, MAGIC *mg)
 	   same function. */
 	mg = mg_find(mg->mg_obj, PERL_MAGIC_isa);

+    assert(mg);
     if (SvTYPE(mg->mg_obj) == SVt_PVAV) { /* multiple stashes */
 	SV **svp = AvARRAY((AV *)mg->mg_obj);
 	I32 items = AvFILLp((AV *)mg->mg_obj) + 1;
@@ -3437,6 +3438,7 @@ Perl_magic_copycallchecker(pTHX_ SV *sv, MAGIC *mg, SV *nsv,

     sv_magic(nsv, &PL_sv_undef, mg->mg_type, NULL, 0);
     nmg = mg_find(nsv, mg->mg_type);
+    assert(nmg);
     if (nmg->mg_flags & MGf_REFCOUNTED) SvREFCNT_dec(nmg->mg_obj);
     nmg->mg_ptr = mg->mg_ptr;
     nmg->mg_obj = SvREFCNT_inc_simple(mg->mg_obj);
diff --git a/mro.c b/mro.c
index 1b37ca7..ccf4bf4 100644
--- a/mro.c
+++ b/mro.c
@@ -638,12 +638,14 @@ Perl_mro_isa_changed_in(pTHX_ HV* stash)
                       hv_storehek(mroisarev, namehek, &PL_sv_yes);
                 }

-                if((SV *)isa != &PL_sv_undef)
+                if ((SV *)isa != &PL_sv_undef) {
+                    assert(namehek);
                     mro_clean_isarev(
                      isa, HEK_KEY(namehek), HEK_LEN(namehek),
                      HvMROMETA(revstash)->isa, HEK_HASH(namehek),
                      HEK_UTF8(namehek)
                     );
+                }
             }
         }
     }
diff --git a/op.c b/op.c
index 796cb03..79621ce 100644
--- a/op.c
+++ b/op.c
@@ -2907,6 +2907,7 @@ S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
 	    S_cant_declare(aTHX_ o);
 	} else if (attrs) {
 	    GV * const gv = cGVOPx_gv(cUNOPo->op_first);
+	    assert(PL_parser);
 	    PL_parser->in_my = FALSE;
 	    PL_parser->in_my_stash = NULL;
 	    apply_attrs(GvSTASH(gv),
@@ -2929,6 +2930,7 @@ S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
     else if (attrs && type != OP_PUSHMARK) {
 	HV *stash;

+        assert(PL_parser);
 	PL_parser->in_my = FALSE;
 	PL_parser->in_my_stash = NULL;

@@ -10229,6 +10231,7 @@ Perl_ck_split(pTHX_ OP *o)
 	op_append_elem(OP_SPLIT, o, newDEFSVOP());

     kid = kid->op_sibling;
+    assert(kid);
     scalar(kid);

     if (!kid->op_sibling)
@@ -10902,6 +10905,7 @@ Perl_cv_set_call_checker(pTHX_ CV *cv, Perl_call_checker ckfun, SV *ckobj)
 	MAGIC *callmg;
 	sv_magic((SV*)cv, &PL_sv_undef, PERL_MAGIC_checkcall, NULL, 0);
 	callmg = mg_find((SV*)cv, PERL_MAGIC_checkcall);
+	assert(callmg);
 	if (callmg->mg_flags & MGf_REFCOUNTED) {
 	    SvREFCNT_dec(callmg->mg_obj);
 	    callmg->mg_flags &= ~MGf_REFCOUNTED;
diff --git a/perlio.c b/perlio.c
index d4c43d0..e6ff9e4 100644
--- a/perlio.c
+++ b/perlio.c
@@ -2225,6 +2225,7 @@ PerlIOBase_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 	PerlIO_funcs * const self = PerlIOBase(o)->tab;
 	SV *arg = NULL;
 	char buf[8];
+	assert(self);
 	PerlIO_debug("PerlIOBase_dup %s f=%p o=%p param=%p\n",
 		     self ? self->name : "(Null)",
 		     (void*)f, (void*)o, (void*)param);
diff --git a/pp_hot.c b/pp_hot.c
index 2cccc48..9c9d1e9 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -3078,6 +3078,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	const HE* const he = hv_fetch_ent(stash, meth, 0, *hashp);
 	if (he) {
 	    gv = MUTABLE_GV(HeVAL(he));
+	    assert(stash);
 	    if (isGV(gv) && GvCV(gv) &&
 		(!GvCVGEN(gv) || GvCVGEN(gv)
                   == (PL_sub_generation + HvMROMETA(stash)->cache_gen)))
@@ -3085,9 +3086,9 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	}
     }

+    assert(stash || packsv);
     gv = gv_fetchmethod_sv_flags(stash ? stash : MUTABLE_HV(packsv),
-			             meth, GV_AUTOLOAD | GV_CROAK);
-
+                                 meth, GV_AUTOLOAD | GV_CROAK);
     assert(gv);

     return isGV(gv) ? MUTABLE_SV(GvCV(gv)) : MUTABLE_SV(gv);
diff --git a/regcomp.c b/regcomp.c
index eaee604..3d49827 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -2007,6 +2007,7 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
     });

     re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, 1);
+    assert(re_trie_maxbuff);
     if (!SvIOK(re_trie_maxbuff)) {
         sv_setiv(re_trie_maxbuff, RE_TRIE_MAXBUF_INIT);
     }
@@ -14920,6 +14921,7 @@ S_set_ANYOF_arg(pTHX_ RExC_state_t* const pRExC_state,
 	av_store(av, 0, (runtime_defns)
 			? SvREFCNT_inc(runtime_defns) : &PL_sv_undef);
 	if (swash) {
+	    assert(cp_list);
 	    av_store(av, 1, swash);
 	    SvREFCNT_dec_NN(cp_list);
 	}
@@ -16609,6 +16611,7 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
         last= plast;

     while (PL_regkind[op] != END && (!last || node < last)) {
+        assert(node);
 	/* While that wasn't END last time... */
 	NODE_ALIGN(node);
 	op = OP(node);
diff --git a/regexec.c b/regexec.c
index 362390b..ffab4f2 100644
--- a/regexec.c
+++ b/regexec.c
@@ -7010,6 +7010,8 @@ no_silent:
                 sv_commit = &PL_sv_yes;
             sv_yes_mark = &PL_sv_no;
         }
+        assert(sv_err);
+        assert(sv_mrk);
         sv_setsv(sv_err, sv_commit);
         sv_setsv(sv_mrk, sv_yes_mark);
     }
@@ -7620,6 +7622,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
                     *only_utf8_locale_ptr = ary[2];
                 }
                 else {
+                    assert(only_utf8_locale_ptr);
                     *only_utf8_locale_ptr = NULL;
                 }

@@ -7641,7 +7644,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
 	    }
 	    else if (doinit && ((si && si != &PL_sv_undef)
                                  || (invlist && invlist != &PL_sv_undef))) {
-
+		assert(si);
 		sw = _core_swash_init("utf8", /* the utf8 package */
 				      "", /* nameless */
 				      si,
diff --git a/universal.c b/universal.c
index a29696d..65e02df 100644
--- a/universal.c
+++ b/universal.c
@@ -67,7 +67,7 @@ S_isa_lookup(pTHX_ HV *stash, const char * const name, STRLEN len, U32 flags)
     if (our_stash) {
 	HEK *canon_name = HvENAME_HEK(our_stash);
 	if (!canon_name) canon_name = HvNAME_HEK(our_stash);
-
+	assert(canon_name);
 	if (hv_common(isa, NULL, HEK_KEY(canon_name), HEK_LEN(canon_name),
 		      HEK_FLAGS(canon_name),
 		      HV_FETCH_ISEXISTS, NULL, HEK_HASH(canon_name))) {
diff --git a/util.c b/util.c
index b90abe5..cd0afb6 100644
--- a/util.c
+++ b/util.c
@@ -850,15 +850,17 @@ Perl_fbm_instr(pTHX_ unsigned char *big, unsigned char *bigend, SV *littlestr, U

     {
 	const MAGIC *const mg = mg_find(littlestr, PERL_MAGIC_bm);
-	const unsigned char * const table = (const unsigned char *) mg->mg_ptr;
 	const unsigned char *oldlittle;

+	assert(mg);
+
 	--littlelen;			/* Last char found by table lookup */

 	s = big + littlelen;
 	little += littlelen;		/* last char */
 	oldlittle = little;
 	if (s < bigend) {
+	    const unsigned char * const table = (const unsigned char *) mg->mg_ptr;
 	    I32 tmp;

 	  top2:
--
1.8.5.2 (Apple Git-48)

13 files changed, 28 insertions, 6 deletions

diff --git a/dist/Data-Dumper/Dumper.xs b/dist/Data-Dumper/Dumper.xs
index 5bc3428c94..e98c6d70d0 100644
--- a/dist/Data-Dumper/Dumper.xs
+++ b/dist/Data-Dumper/Dumper.xs
@@ -642,6 +642,7 @@ DD_dump(pTHX_ SV *val, const char *name, STRLEN namelen, SV *retval, HV *seenhv,
 	    else {
 	      sv_pattern = val;
 	    }
+	    assert(sv_pattern);
 	    rval = SvPV(sv_pattern, rlen);
 	    rend = rval+rlen;
 	    slash = rval;
diff --git a/dump.c b/dump.c
index 59be3e0a25..c2d72fdd40 100644
--- a/dump.c
+++ b/dump.c
@@ -471,6 +471,7 @@ Perl_sv_peek(pTHX_ SV *sv)
   finish:
     while (unref--)
 	sv_catpv(t, ")");
+    /* XXX when is sv ever NULL? */
     if (TAINTING_get && SvTAINTED(sv))
 	sv_catpv(t, " [tainted]");
     return SvPV_nolen(t);
diff --git a/ext/Devel-Peek/Peek.xs b/ext/Devel-Peek/Peek.xs
index 679efa5d06..b20fa94687 100644
--- a/ext/Devel-Peek/Peek.xs
+++ b/ext/Devel-Peek/Peek.xs
@@ -450,6 +450,7 @@ PPCODE:
 BOOT:
 {
     CV * const cv = get_cvn_flags("Devel::Peek::Dump", 17, 0);
+    assert(cv);
     cv_set_call_checker(cv, S_ck_dump, (SV *)cv);
 
     XopENTRY_set(&my_xop, xop_name, "Dump");
diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index fb5e3662dc..1e750c3653 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -2095,6 +2095,7 @@ newCONSTSUB(stash, name, flags, sv)
                break;
         }
         EXTEND(SP, 2);
+        assert(mycv);
         PUSHs( CvCONST(mycv) ? &PL_sv_yes : &PL_sv_no );
         PUSHs((SV*)CvGV(mycv));
 
diff --git a/mg.c b/mg.c
index 76912bd9ce..7f3339a93e 100644
--- a/mg.c
+++ b/mg.c
@@ -1675,6 +1675,7 @@ Perl_magic_clearisa(pTHX_ SV *sv, MAGIC *mg)
 	   same function. */
 	mg = mg_find(mg->mg_obj, PERL_MAGIC_isa);
 
+    assert(mg);
     if (SvTYPE(mg->mg_obj) == SVt_PVAV) { /* multiple stashes */
 	SV **svp = AvARRAY((AV *)mg->mg_obj);
 	I32 items = AvFILLp((AV *)mg->mg_obj) + 1;
@@ -3437,6 +3438,7 @@ Perl_magic_copycallchecker(pTHX_ SV *sv, MAGIC *mg, SV *nsv,
 
     sv_magic(nsv, &PL_sv_undef, mg->mg_type, NULL, 0);
     nmg = mg_find(nsv, mg->mg_type);
+    assert(nmg);
     if (nmg->mg_flags & MGf_REFCOUNTED) SvREFCNT_dec(nmg->mg_obj);
     nmg->mg_ptr = mg->mg_ptr;
     nmg->mg_obj = SvREFCNT_inc_simple(mg->mg_obj);
diff --git a/mro.c b/mro.c
index 1b37ca7cd6..ccf4bf41f6 100644
--- a/mro.c
+++ b/mro.c
@@ -638,12 +638,14 @@ Perl_mro_isa_changed_in(pTHX_ HV* stash)
                       hv_storehek(mroisarev, namehek, &PL_sv_yes);
                 }
 
-                if((SV *)isa != &PL_sv_undef)
+                if ((SV *)isa != &PL_sv_undef) {
+                    assert(namehek);
                     mro_clean_isarev(
                      isa, HEK_KEY(namehek), HEK_LEN(namehek),
                      HvMROMETA(revstash)->isa, HEK_HASH(namehek),
                      HEK_UTF8(namehek)
                     );
+                }
             }
         }
     }
diff --git a/op.c b/op.c
index 75aae398bd..266ac8c82a 100644
--- a/op.c
+++ b/op.c
@@ -2912,6 +2912,7 @@ S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
 	    S_cant_declare(aTHX_ o);
 	} else if (attrs) {
 	    GV * const gv = cGVOPx_gv(cUNOPo->op_first);
+	    assert(PL_parser);
 	    PL_parser->in_my = FALSE;
 	    PL_parser->in_my_stash = NULL;
 	    apply_attrs(GvSTASH(gv),
@@ -2934,6 +2935,7 @@ S_my_kid(pTHX_ OP *o, OP *attrs, OP **imopsp)
     else if (attrs && type != OP_PUSHMARK) {
 	HV *stash;
 
+        assert(PL_parser);
 	PL_parser->in_my = FALSE;
 	PL_parser->in_my_stash = NULL;
 
@@ -10238,6 +10240,7 @@ Perl_ck_split(pTHX_ OP *o)
 	op_append_elem(OP_SPLIT, o, newDEFSVOP());
 
     kid = kid->op_sibling;
+    assert(kid);
     scalar(kid);
 
     if (!kid->op_sibling)
@@ -10912,6 +10915,7 @@ Perl_cv_set_call_checker(pTHX_ CV *cv, Perl_call_checker ckfun, SV *ckobj)
 	MAGIC *callmg;
 	sv_magic((SV*)cv, &PL_sv_undef, PERL_MAGIC_checkcall, NULL, 0);
 	callmg = mg_find((SV*)cv, PERL_MAGIC_checkcall);
+	assert(callmg);
 	if (callmg->mg_flags & MGf_REFCOUNTED) {
 	    SvREFCNT_dec(callmg->mg_obj);
 	    callmg->mg_flags &= ~MGf_REFCOUNTED;
diff --git a/perlio.c b/perlio.c
index 4dc3ec36b5..2ce8ac162c 100644
--- a/perlio.c
+++ b/perlio.c
@@ -2227,6 +2227,7 @@ PerlIOBase_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 	PerlIO_funcs * const self = PerlIOBase(o)->tab;
 	SV *arg = NULL;
 	char buf[8];
+	assert(self);
 	PerlIO_debug("PerlIOBase_dup %s f=%p o=%p param=%p\n",
 		     self ? self->name : "(Null)",
 		     (void*)f, (void*)o, (void*)param);
diff --git a/pp_hot.c b/pp_hot.c
index 2cccc48bed..9c9d1e9fcc 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -3078,6 +3078,7 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	const HE* const he = hv_fetch_ent(stash, meth, 0, *hashp);
 	if (he) {
 	    gv = MUTABLE_GV(HeVAL(he));
+	    assert(stash);
 	    if (isGV(gv) && GvCV(gv) &&
 		(!GvCVGEN(gv) || GvCVGEN(gv)
                   == (PL_sub_generation + HvMROMETA(stash)->cache_gen)))
@@ -3085,9 +3086,9 @@ S_method_common(pTHX_ SV* meth, U32* hashp)
 	}
     }
 
+    assert(stash || packsv);
     gv = gv_fetchmethod_sv_flags(stash ? stash : MUTABLE_HV(packsv),
-			             meth, GV_AUTOLOAD | GV_CROAK);
-
+                                 meth, GV_AUTOLOAD | GV_CROAK);
     assert(gv);
 
     return isGV(gv) ? MUTABLE_SV(GvCV(gv)) : MUTABLE_SV(gv);
diff --git a/regcomp.c b/regcomp.c
index 94dfd55ecd..e3a01b6b37 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -2007,6 +2007,7 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
     });
 
     re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, 1);
+    assert(re_trie_maxbuff);
     if (!SvIOK(re_trie_maxbuff)) {
         sv_setiv(re_trie_maxbuff, RE_TRIE_MAXBUF_INIT);
     }
@@ -14923,6 +14924,7 @@ S_set_ANYOF_arg(pTHX_ RExC_state_t* const pRExC_state,
 	av_store(av, 0, (runtime_defns)
 			? SvREFCNT_inc(runtime_defns) : &PL_sv_undef);
 	if (swash) {
+	    assert(cp_list);
 	    av_store(av, 1, swash);
 	    SvREFCNT_dec_NN(cp_list);
 	}
@@ -16612,6 +16614,7 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
         last= plast;
 
     while (PL_regkind[op] != END && (!last || node < last)) {
+        assert(node);
 	/* While that wasn't END last time... */
 	NODE_ALIGN(node);
 	op = OP(node);
diff --git a/regexec.c b/regexec.c
index 7d6827aa81..d2994d4222 100644
--- a/regexec.c
+++ b/regexec.c
@@ -7010,6 +7010,8 @@ no_silent:
                 sv_commit = &PL_sv_yes;
             sv_yes_mark = &PL_sv_no;
         }
+        assert(sv_err);
+        assert(sv_mrk);
         sv_setsv(sv_err, sv_commit);
         sv_setsv(sv_mrk, sv_yes_mark);
     }
@@ -7620,6 +7622,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
                     *only_utf8_locale_ptr = ary[2];
                 }
                 else {
+                    assert(only_utf8_locale_ptr);
                     *only_utf8_locale_ptr = NULL;
                 }
 
@@ -7641,7 +7644,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
 	    }
 	    else if (doinit && ((si && si != &PL_sv_undef)
                                  || (invlist && invlist != &PL_sv_undef))) {
-
+		assert(si);
 		sw = _core_swash_init("utf8", /* the utf8 package */
 				      "", /* nameless */
 				      si,
diff --git a/universal.c b/universal.c
index a29696d840..65e02dfcce 100644
--- a/universal.c
+++ b/universal.c
@@ -67,7 +67,7 @@ S_isa_lookup(pTHX_ HV *stash, const char * const name, STRLEN len, U32 flags)
     if (our_stash) {
 	HEK *canon_name = HvENAME_HEK(our_stash);
 	if (!canon_name) canon_name = HvNAME_HEK(our_stash);
-
+	assert(canon_name);
 	if (hv_common(isa, NULL, HEK_KEY(canon_name), HEK_LEN(canon_name),
 		      HEK_FLAGS(canon_name),
 		      HV_FETCH_ISEXISTS, NULL, HEK_HASH(canon_name))) {
diff --git a/util.c b/util.c
index ad007b9030..42926b37f7 100644
--- a/util.c
+++ b/util.c
@@ -850,15 +850,17 @@ Perl_fbm_instr(pTHX_ unsigned char *big, unsigned char *bigend, SV *littlestr, U
 
     {
 	const MAGIC *const mg = mg_find(littlestr, PERL_MAGIC_bm);
-	const unsigned char * const table = (const unsigned char *) mg->mg_ptr;
 	const unsigned char *oldlittle;
 
+	assert(mg);
+
 	--littlelen;			/* Last char found by table lookup */
 
 	s = big + littlelen;
 	little += littlelen;		/* last char */
 	oldlittle = little;
 	if (s < bigend) {
+	    const unsigned char * const table = (const unsigned char *) mg->mg_ptr;
 	    I32 tmp;
 
 	  top2: