add Perl_magic_freeutf8() magic vtable method

S_mg_free_struct() has a workaround to free mg->mg_ptr in
PERL_MAGIC_utf8 even if mg_len is zero.

Move this logic into a new magic vtable free method instead, so that
S_mg_free_struct() (which gets called for every type of magic) doesn't
have the overhead of checking every time for mg->mg_type ==
PERL_MAGIC_utf8.

1 files changed, 17 insertions, 1 deletions

diff --git a/mg.c b/mg.c
index c7088f8446..4f199af423 100644
--- a/mg.c
+++ b/mg.c
@@ -555,7 +555,7 @@ S_mg_free_struct(pTHX_ SV *sv, MAGIC *mg)
 	vtbl->svt_free(aTHX_ sv, mg);
 
     if (mg->mg_ptr && mg->mg_type != PERL_MAGIC_regex_global) {
-	if (mg->mg_len > 0 || mg->mg_type == PERL_MAGIC_utf8)
+	if (mg->mg_len > 0)
 	    Safefree(mg->mg_ptr);
 	else if (mg->mg_len == HEf_SVKEY)
 	    SvREFCNT_dec(MUTABLE_SV(mg->mg_ptr));
@@ -2675,6 +2675,22 @@ Perl_magic_setutf8(pTHX_ SV *sv, MAGIC *mg)
 }
 
 int
+Perl_magic_freeutf8(pTHX_ SV *sv, MAGIC *mg)
+{
+    PERL_ARGS_ASSERT_MAGIC_FREEUTF8;
+    PERL_UNUSED_ARG(sv);
+
+    /* utf8 magic uses mg_len as a string length rather than a buffer
+     * length, so we need to free even with mg_len == 0: hence we can't
+     * rely on standard magic free handling */
+    assert(mg->mg_type == PERL_MAGIC_utf8 && mg->mg_len >= -1);
+    Safefree(mg->mg_ptr);
+    mg->mg_ptr = NULL;
+    return 0;
+}
+
+
+int
 Perl_magic_setlvref(pTHX_ SV *sv, MAGIC *mg)
 {
     const char *bad = NULL;