Disallow coderef in $PerlIO::encoding::fallback

Encode allows one to pass a coderef instead of a set of flags to handle.
This however doesn't allow one to pass STOP_AT_PARTIAL, which means it
has always been buggy on buffer boundaries. With my new automatic
STOP_AT_PARTIAL passing this would result in an unpredictable value.
Instead we now disallow it in PerlIO::encoding.

1 files changed, 2 insertions, 0 deletions

diff --git a/ext/PerlIO-encoding/encoding.xs b/ext/PerlIO-encoding/encoding.xs
index 1db9eba81e..720808d87d 100644
--- a/ext/PerlIO-encoding/encoding.xs
+++ b/ext/PerlIO-encoding/encoding.xs
@@ -168,6 +168,8 @@ PerlIOEncode_pushed(pTHX_ PerlIO * f, const char *mode, SV * arg, PerlIO_funcs *
     }
 
     e->chk = newSVsv(get_sv("PerlIO::encoding::fallback", 0));
+    if (SvROK(e->chk))
+        Perl_croak(aTHX_ "PerlIO::encoding::fallback must be an integer");
     SvUV_set(e->chk, SvUV(e->chk) | encode_stop_at_partial);
     e->inEncodeCall = 0;