[perl #114410] Reset utf8 pos cache on get

If a scalar is gmagical, then the string buffer could change without
the utf8 pos cache being updated.

So it should respond to get-magic, not just set-magic.  Actually add-
ing get-magic to the utf8 magic vtable would cause all scalars with
this magic to be flagged gmagical.  Instead, in magic_get, we can call
magic_setutf8.

1 files changed, 4 insertions, 0 deletions

diff --git a/mg.c b/mg.c
index 3972a87be6..089f9c6e26 100644
--- a/mg.c
+++ b/mg.c
@@ -213,6 +213,10 @@ Perl_mg_get(pTHX_ SV *sv)
 	    if (mg->mg_flags & MGf_GSKIP)
 		(SSPTR(mgs_ix, MGS *))->mgs_magical = 0;
 	}
+	else if (vtbl == &PL_vtbl_utf8) {
+	    /* get-magic can reallocate the PV */
+	    magic_setutf8(sv, mg);
+	}
 
 	mg = nextmg;