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Re: [GSoC][match-and-simplify] put check for EOF
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Prathamesh Kulkarni <bilbotheelffriend at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Maxim Kuvyrkov <maxim dot kuvyrkov at linaro dot org>, Tom Tromey <tromey at redhat dot com>
- Date: Fri, 8 Aug 2014 14:15:32 +0200
- Subject: Re: [GSoC][match-and-simplify] put check for EOF
- Authentication-results: sourceware.org; auth=none
- References: <CAJXstsBHDKa-6xENNrTAD75M1bMU5iPzrw9fAAKg0cPmCoxcEQ at mail dot gmail dot com>
On Fri, Aug 8, 2014 at 11:50 AM, Prathamesh Kulkarni
<bilbotheelffriend@gmail.com> wrote:
> Put check for EOF in parse_for and parse_if,
> else it results in segmentation fault.
>
> eg:
> (if (0)
> <eof>
>
> Not sure why it segfaults.
Hmm, I think this is a bug in libcpp which seems to
crash when you do cpp_peek_token (r, 0); cpp_peek_token (r, 0);
with the first peek returning a CPP_EOF token. The first peek
then resets r->buffer via
#0 _cpp_pop_buffer (pfile=0x67e560)
at /space/rguenther/src/svn/match-and-simplify/libcpp/directives.c:2575
#1 0x0000000000423011 in _cpp_get_fresh_line (pfile=0x67e560)
at /space/rguenther/src/svn/match-and-simplify/libcpp/lex.c:2146
#2 0x00000000004230f1 in _cpp_lex_direct (pfile=0x67e560)
at /space/rguenther/src/svn/match-and-simplify/libcpp/lex.c:2193
#3 0x0000000000422e05 in _cpp_lex_token (pfile=0x67e560)
at /space/rguenther/src/svn/match-and-simplify/libcpp/lex.c:2067
#4 0x0000000000422ac0 in cpp_peek_token (pfile=0x67e560, index=0)
at /space/rguenther/src/svn/match-and-simplify/libcpp/lex.c:1986
It seems that cpp_peek_token (r, 10) and hitting EOF somewhere
inbetween would show the same behavior.
Tom?
Richard.
> I got following back-trace (in gdb):
>
> #0 _cpp_lex_direct (pfile=pfile@entry=0x66f560) at ../../src/libcpp/lex.c:2183
> #1 0x000000000041d50c in _cpp_lex_token (pfile=pfile@entry=0x66f560)
> at ../../src/libcpp/lex.c:2067
> #2 0x000000000041d630 in cpp_peek_token (pfile=pfile@entry=0x66f560,
> index=index@entry=0) at ../../src/libcpp/lex.c:1986
> #3 0x000000000040e315 in peek (r=<optimized out>) at
> ../../src/gcc/genmatch.c:1820
> #4 parse_if (r=r@entry=0x66f560, simplifiers=...) at
> ../../src/gcc/genmatch.c:2176
> #5 0x000000000040de30 in parse_pattern (r=0x66f560, simplifiers=...)
> at ../../src/gcc/genmatch.c:2207
> #6 0x0000000000407738 in main (argc=6747488, argv=0x68b350) at
> ../../src/gcc/genmatch.c:2275
>
> This patch fixes the seg-fault by explicitly checking for EOF in parse_if
> and parse_for, however I am not sure if this is the right approach to fix it.
> I suppose parse_pattern should give an error here,
> since it expects CPP_OPEN_PAREN but receives CPP_EOF.
>
> * genmatch.c (parse_if): Put check for EOF.
> (parse_for): Likewise.
>
> Thanks,
> Prathamesh