Add SIGTRAP to the handled signals on Linux

Add SIGTRAP to the handled signals on Linux

BUG=none

[jochen]

Mark, wdyt

I'm currently adding breakpad to content shell and noticed that LOG(FATAL) in
debug mode doesn't produce a crash dump.

[Mark Mentovai]

Does this impact breakpoints in a debugger?

[jochen]

On 2013/10/25 19:45:08, Mark Mentovai wrote:
> Does this impact breakpoints in a debugger?

hum yes, int 3 also triggers sigtrap

not sure whether running in a debugger and running breakpad at the same time
works at all?

I guess alternatively, I could change
https://code.google.com/p/chromium/codesearch#chromium/src/base/logging.cc&l=666
to do something more radical to crash.

[jochen]

actually, CHECK() etc also uses DebugBreak, so it would be really nice if we had
a way to capture a dump on sigtrap.

[Mark Mentovai]

jochen wrote:
> On 2013/10/25 19:45:08, Mark Mentovai wrote:
> > Does this impact breakpoints in a debugger?
> 
> hum yes, int 3 also triggers sigtrap
> 
> not sure whether running in a debugger and running breakpad at the same time
> works at all?
> 
> I guess alternatively, I could change
>
https://code.google.com/p/chromium/codesearch#chromium/src/base/logging.cc&l=666
> to do something more radical to crash.

Instead of int3, you could make it emit ud2, which would raise SIGILL. With gcc
and clang, __builtin_trap() should give you one of those on x86 without any
inline asm.