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

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
04e40fd337a244ee77ef9553985e9398ff0344af ).

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>

diff --git a/src/glsl/glcpp/glcpp-lex.l b/src/glsl/glcpp/glcpp-lex.l
index 98d500ec0be18cfda86c03acc1dd215f49526b2f..fa9aa50691280df8e8324b58abb44ea12c19aaa7 100644 (file)
--- 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;
 }