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 Piglit's 16385-consecutive-chars and
17000-consecutive-chars-identifier tests.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82472
Signed-off-by: Carl Worth <cwo...@cworth.org>
Approach-suggested-by: Kenneth Graunke <kenn...@whitecape.org>
CC: Kenneth Graunke <kenn...@whitecape.org>
---
Thanks for chasing down the fix for this regression of mine, Ken.
I am embarrassed that I clearly didn't run piglit enough while testing my
original branch.
With your fix above, there is some state that's not updated as it should
be when returning a NEWLINE token, (such as incrementing yylineno, etc.).
I tried to improve things to update all that state, but it proved
problematic, (putting the state updates in a common function doesn't
work because only the outer lexing function has access to local variables
like yylineno).
The alternate approach here was your recommendation, of course.
src/glsl/glcpp/glcpp-lex.l | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/src/glsl/glcpp/glcpp-lex.l b/src/glsl/glcpp/glcpp-lex.l
index 98d500e..aaef7b8 100644
--- a/src/glsl/glcpp/glcpp-lex.l
+++ b/src/glsl/glcpp/glcpp-lex.l
@@ -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;
}
--
2.0.0
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