Do not read /proc/self/exe before forking if Chrome is ran under Valgrind....

Do not read /proc/self/exe before forking if Chrome is ran under Valgrind.
This should prevent ui_tests from crashing under Valgrind on Linux.
This fix was suggested by kcc (see the discussion of issue 28439)

BUG=28439
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=71590

[Alexander Potapenko, 2011-01-14 13:42:44]

Hi Evan,

could you please take a look?

[evanm, 2011-01-14 17:19:20]

http://codereview.chromium.org/6331002/diff/1/chrome/common/child_process_hos...
File chrome/common/child_process_host.cc (right):

http://codereview.chromium.org/6331002/diff/1/chrome/common/child_process_hos...
chrome/common/child_process_host.cc:69: PathService::Get(base::FILE_EXE,
&child_path);
Do we know if this returns /proc/self/exe too?  My vague memory is that it reads
the /proc/self/exe symlink and returns that path...

[kcc1, 2011-01-14 17:20:55]

On Fri, Jan 14, 2011 at 8:19 PM, <evanm@google.com> wrote:

>
>
>
http://codereview.chromium.org/6331002/diff/1/chrome/common/child_process_hos...
> File chrome/common/child_process_host.cc (right):
>
>
>
http://codereview.chromium.org/6331002/diff/1/chrome/common/child_process_hos...
> chrome/common/child_process_host.cc:69: PathService::Get(base::FILE_EXE,
> &child_path);
> Do we know if this returns /proc/self/exe too?  My vague memory is that
> it reads the /proc/self/exe symlink and returns that path...

...which actually returns /blah/blah/chrome, which works fine for valgrind
(confirmed)

>
>
> http://codereview.chromium.org/6331002/
>

[evanm, 2011-01-14 17:22:28]

On 2011/01/14 17:20:55, kcc1 wrote:
> > Do we know if this returns /proc/self/exe too?  My vague memory is that
> > it reads the /proc/self/exe symlink and returns that path...
> 
> ...which actually returns /blah/blah/chrome, which works fine for valgrind
> (confirmed)

Weird!  So exec'ing /proc/self/exe execs valgrind, but reading the
/proc/self/exe symlink gives you the real path?

LGTM then

[Alexander Potapenko, 2011-01-14 18:10:34]

> Weird!  So exec'ing /proc/self/exe execs valgrind, but reading the
> /proc/self/exe symlink gives you the real path?
Yes, according to
http://old.nabble.com/valgrind:-failed-in-UME-with-error-22-(Invalid-argument...
> 
> LGTM then