Perl_mode_from_discipline must update len. (else SEGV)

Diagnosis and patch from clkao

p4raw-id: //depot/perl@23076

1 files changed, 1 insertions, 0 deletions

diff --git a/doio.c b/doio.c
index 98e7204768..a551d05819 100644
--- a/doio.c
+++ b/doio.c
@@ -1172,6 +1172,7 @@ fail_discipline:
 #ifndef PERLIO_LAYERS
 		Perl_croak(aTHX_ "IO layers (like '%.*s') unavailable", end-s, s);
 #else
+		len -= end-s;
 		s = end;
 #endif
 	    }