debug info problems about sanitizers HOT 12 CLOSED

-Stability+1: crashes in the libc stack unwinder on Android. Only happen when main()
is instrumented. I can only explain this by the incorrect debug info. May be related
to http://llvm.org/bugs/show_bug.cgi?id=11468 (incorrect debug info with aligned stack
variables).

Notes on the progress:
Exceptions (PR11468): Call frame information is incorrect in case the stack is aligned.
I see no short quick fix for this bug at the moment. eugenis@, does this happen on
ARM? The code that emits function prologue is target-specific, so probably it's incorrect
both on X86 and ARM.

Debug Info Quality: fixed little bug with debug info in presence of aligned stack,
but it didn't help ASan - have to dig deeper.

Debug Info Size: Clang option -gline-tables-only submitted to trunk and is being tested.
This option increases the size of the binary by about 2x (instead of 4-5x with regular
-g) and produces stack traces with files and line numbers.

Thanks for working on this. The "Debug info quality" problem (11818) seems to be the
most severe for us at the moment because it makes it pretty much impossible to debug
any ASan failures with GDB in Firefox or Spidermonkey.

-gline-tables-only looks good so far, with the only problem that it does not save the

full function names.
I.e. instead of AAA::BBB::CCC(int, int) it will just have CCC.
This is not a big deal if we can extract the function name from the symbol in the binary,
but it hurts if we have some inlined frames.
-gline-tables-only can be fixed to actually store the full function names, but it will
cost some debug info size. 
Alexey, please measure the difference and update this bug. 

PR11468 is fixed in r160248.

Is there any update on the second point? I'm still seeing lots of "<optimized out>"
in debug-only builds. I was just trying again to debug an ASan failure under GDB but
it's pretty much impossible.

No, full debug info (the ability to trace variable/argument values) is still broken
with ASan. We hope to fix this soon, but I can't give the exact date when it is done...

r169984 makes ASan + "-g" + gdb much more usable (I can now observe values of local
variables and function arguments). I would be happy to hear from decoder.oh if it works
for Firefox/Spidermonkey. Closing this issue for now. Feel free to file debug info
problems or bugs as separate (hopefully, not major) issues.

Can we get Chromium's clang revision rolled past this change. Please. Pretty please.

Right now Chromium is at clang r169803, according to tools/clang/scripts/update.sh

Stephen, you need this for debugging, right?
You can refer to http://dev.chromium.org/developers/testing/addresssanitizer for the
instructions on how to build Chromium with a custom Clang (and code.google.com/p/address-sanitizer/wiki/HowToBuild
for Clang build instructions).

Moreover, you can fix tools/clang/scripts/update.sh to point to this revision (you'll
also need to work around the Android flag in that script). Then running update.sh will
download and build the corresponding Clang version for you.

Adding Project:AddressSanitizer as part of GitHub migration.