[PATCH, DOC] Document ASAN_OPTIONS="halt_on_error" env variable.

[Yury Gribov]

On 05/11/2016 05:13 PM, Martin Liška wrote:
> Hello.
>
> It's bit confusing for a use that -fsanitize-recover=address does not recover
> an instrumented binary. As a default value of halt_on_error is set to 0 for address sanitizer,
> the binary fails on a first error.

I'm the guy behind -fsanitize-recover=address so let me explain.

Error recovery requires changes both to compiler (insert calls to 
recovering __asan_report_error_X_noabort rather than noreturning 
__asan_report_error_X) and runtime (do not abort when detecting overflow 
inside intercepted API like memcpy). -fsanitize-recover controls the 
compiler side, whereas halt_on_error=0 controls the runtime side.

Unfortunately currently there is no way to inform runtime library that 
compiled code would like it to continue execution after detecting error. 
Actually it's not clear how to do that properly because different parts 
of application could be compiled with different recovery settings (e.g. 
a.c with recovery and b.c without) making it hard to understand what 
behavior user would expect from runtime library interceptors.

> Following patch attempts to explain the ENV variable.
>
> Ready for trunk?

LGTM (but I'm not a maintainer and do not have approve right).

> Thanks,
> Martin
>