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glcpp: Don't use alternation in the lookahead for empty pragmas.

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We've found that there's a buffer overrun bug in flex that's triggered by
using alternation in a lookahead pattern.

Fortunately, we don't need to match the exact {NEWLINE} expression to
detect an empty pragma. It suffices to verify that there are no non-space
characters before any newline character. So we can use a simple [\r\n] to
get the desired behavior while avoiding the flex bug.

Fixes the regression of piglit's 17000-consecutive-chars-identifier test,
(which has been crashing since commit
04e40fd337 ).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82472
Signed-off-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

CC: <mesa-stable@lists.freedesktop.org>
This commit is contained in:
Carl Worth 2014-08-18 11:36:12 -07:00
parent 97d03b9366
commit 23163df24c
1 changed files with 8 additions and 2 deletions
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10
src/glsl/glcpp/glcpp-lex.l
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@ -289,8 +289,14 @@ HEXADECIMAL_INTEGER 0[xX][0-9a-fA-F]+[uU]?
}
/* Swallow empty #pragma directives, (to avoid confusing the
* downstream compiler). */
<HASH>pragma{HSPACE}*/{NEWLINE} {
* downstream compiler).
*
* Note: We use a simple regular expression for the lookahead
* here. Specifically, we cannot use the complete {NEWLINE} expression
* since it uses alternation and we've found that there's a flex bug
* where using alternation in the lookahead portion of a pattern
* triggers a buffer overrun. */
<HASH>pragma{HSPACE}*/[\r\n] {
BEGIN INITIAL;
}