Fix perl bug #17920 : a case of parser coredump.

The fix is to disable Perl_block_start and Perl_block_end
when the yacc parser has encountered errors. This prevents
corruption of the internal stack, at the expense of correctness,
but this doesn't matter as the code is unparseable anyway.

p4raw-id: //depot/perl@18166

1 files changed, 4 insertions, 0 deletions

diff --git a/op.c b/op.c
index 9f9722722f..c3aee1e68b 100644
--- a/op.c
+++ b/op.c
@@ -1734,6 +1734,8 @@ int
 Perl_block_start(pTHX_ int full)
 {
     int retval = PL_savestack_ix;
+    /* If there were syntax errors, don't try to start a block */
+    if (PL_yynerrs) return retval;
 
     pad_block_start(full);
     SAVEHINTS();
@@ -1757,6 +1759,8 @@ Perl_block_end(pTHX_ I32 floor, OP *seq)
     int needblockscope = PL_hints & HINT_BLOCK_SCOPE;
     line_t copline = PL_copline;
     OP* retval = scalarseq(seq);
+    /* If there were syntax errors, don't try to close a block */
+    if (PL_yynerrs) return retval;
     if (!seq) {
 	/* scalarseq() gave us an OP_STUB */
 	retval->op_flags |= OPf_PARENS;