(perl #126203) avoid potential leaks on quadmath_snprintf() failure

In the unlikely case quadmath_snprintf() fails both sv_vcatpvfn_flags()
and my_snprintf() could leak the temp format string returned by
quadmath_format_single() if quadmath_format_single() had to rebuild
the format.

Getting quadmath_snprintf() to fail in this context seems impractical,
but future changes may make it happen, so clean up after ourselves.

1 files changed, 4 insertions, 1 deletions

diff --git a/sv.c b/sv.c
index 339fa1b7d3..61bf3e10c9 100644
--- a/sv.c
+++ b/sv.c
@@ -12881,8 +12881,11 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
                         Perl_croak_nocontext("panic: quadmath invalid format \"%s\"", ptr);
                     elen = quadmath_snprintf(PL_efloatbuf, PL_efloatsize,
                                              qfmt, nv);
-                    if ((IV)elen == -1)
+                    if ((IV)elen == -1) {
+                        if (qfmt != qptr)
+                            SAVEFREEPV(qfmt);
                         Perl_croak_nocontext("panic: quadmath_snprintf failed, format \"%s\"", qfmt);
+                    }
                     if (qfmt != ptr)
                         Safefree(qfmt);
                 }