[perl #29070] Add vstring set-magic

Some operators, like pp_complement, assign their argument to TARG
(which copies vstring magic), modify it in place, and then call set-
magic.  That’s supposed to work, but vstring magic was remaining as it
was, such that ~v7 would still be treated as "v7" by vstring-aware
code, even though the resulting string is not "\7".

This commit adds vstring set-magic that checks to see whether the pv
still matches the vstring.  It cannot simply free the vstring magic,
as that would prevent $x=v0 from working.

1 files changed, 13 insertions, 0 deletions

diff --git a/mg.c b/mg.c
index 3432dfe5c4..31330dd903 100644
--- a/mg.c
+++ b/mg.c
@@ -2295,6 +2295,19 @@ Perl_magic_setvec(pTHX_ SV *sv, MAGIC *mg)
 }
 
 int
+Perl_magic_setvstring(pTHX_ SV *sv, MAGIC *mg)
+{
+    PERL_ARGS_ASSERT_MAGIC_SETVSTRING;
+
+    if (SvPOKp(sv)) {
+	SV * const vecsv = sv_newmortal();
+	scan_vstring(mg->mg_ptr, mg->mg_ptr + mg->mg_len, vecsv);
+	if (sv_eq_flags(vecsv, sv, 0 /*nomg*/)) return 0;
+    }
+    return sv_unmagic(sv, mg->mg_type);
+}
+
+int
 Perl_magic_getdefelem(pTHX_ SV *sv, MAGIC *mg)
 {
     dVAR;