[LLVMdev] asan coverage

[Bob Wilson]

The bit code file produced by the stage 1 compiler for one of the files in the clang driver is corrupt and causes the linker for stage 2 to crash.

On Nov 14, 2013, at 10:13 PM, Kostya Serebryany <kcc at google.com> wrote:

> What are the symptoms?
> 
> On Fri, Nov 15, 2013 at 9:37 AM, Bob Wilson <bob.wilson at apple.com> wrote:
>> I’m waiting to see if this fixes the buildbots.  Unfortunately, because they were failing all day, there are a bunch of other regressions that have come up, and I’m still working through them.  It takes quite a while to run a bootstrapped LTO clang build, so it will take a while longer.
>> 
>> I don’t have any other useful information at this point, and I share your puzzlement about how your changes could possibly break the compiler.  My only hypothesis is some sort of memory corruption.
>> 
>> I will keep you posted.
>> 
>> On Nov 14, 2013, at 9:22 PM, Kostya Serebryany <kcc at google.com> wrote:
>> 
>>> Also, when are you planing to "reapply the changes or help debug"?
>>> 
>>> On Fri, Nov 15, 2013 at 9:15 AM, Kostya Serebryany <kcc at google.com> wrote:
>>>> On Fri, Nov 15, 2013 at 7:26 AM, Bob Wilson <bob.wilson at apple.com> wrote:
>>>>> Hi Kostya,
>>>>> 
>>>>> Thanks for the heads-up on this.  I haven’t had a chance to look into the
>>>>> details yet, but it looks like these patches may be breaking our
>>>>> bootstrapped LTO build.  Our buildbots have been failing all day, and we’re
>>>>> still trying to figure out the problem.  I’m going to speculatively revert
>>>>> those changes, since they were the only patches on the buildbot blame list.
>>>>> I will either reapply the changes or help debug the problem.
>>>> 
>>>> How could this possibly affect your LTO build?
>>>> The option is off by default.
>>>> Do you have any details, logs, etc?
>>>> 
>>>>> 
>>>>> —Bob
>>>>> 
>>>>> On Nov 14, 2013, at 5:42 AM, Kostya Serebryany <kcc at google.com> wrote:
>>>>> 
>>>>> Bob, Justin,
>>>>> 
>>>>> I've just committed a poor man's coverage implementation that works with
>>>>> asan.
>>>>> http://llvm.org/viewvc/llvm-project?rev=194701&view=rev
>>>>> http://llvm.org/viewvc/llvm-project?rev=194702&view=rev
>>>>> It provides only function-level boolean coverage (i.e. no counters, just
>>>>> "visited or not"),
>>>>> but is very fast and very simple (no extra sections to the binary file, etc)
>>>>> I've tried it for Chrome's content_shell (huge and heavy binary) and the
>>>>> overhead
>>>>> is negligible at both run-time and shutdown-time.
>>>>> 
>>>>> We'll be evaluating this implementation and collecting usage stats.
>>>>> Maybe we want to implement something simple like this in the Clang coverage.
>>>>> 
>>>>> --kcc
>>>>> 
>>>>> 
>>