Bug 22456 – Bison versions under 2.2 produce crashing CSSGrammar code for ARM

• Status: RESOLVED
• Resolution: FIXED
• Component: WebKitGTK

[Kalle Vahlman]

After agonizing bug hunting week, I found out that bison versions earlier than 2.2 produce faulty code that crashes on ARM CPUs from CSSGrammar.y. There's a similar issue reported as bug 18538 but that's probably not exactly the same thing as here.

git-bisecting pointed http://trac.webkit.org/changeset/35351 as the revision that introduces the crashing.

As I have no mad bison skillz, determining if the actual cause is a bison bug or something CSSGrammar.y could fix is a bit hard. But at the very least we could add a check to configure.ac for this and error out.

[Kalle Vahlman]

Created attachment 25427 [details]
Backtrace of the crash

[Kalle Vahlman]

Created attachment 25428 [details]
Differences in generated code

This diff shows the changes between a non-working (bison v1.875d) and working (bison v2.3) generated code (in case someone wants to get to the bottom of this...).

[Kalle Vahlman]

Created attachment 25429 [details]
And finally, a patch to check for bison version >=2.2 when compiling for ARM

[Darin Adler]

Comment on attachment 25429 [details]
And finally, a patch to check for bison version >=2.2 when compiling for ARM

r=me

[Jan Alonzo]

Landed in r38782. Thanks!