add a way to get code coverage

add a way to get code coverage

BUG=

[mtklein, 2013-09-12 17:11:44]

Hopefully this should be obvious how to generalize this to run on a bot and to
get the full merged coverage of bench, bench_pictures, tests, and gm?

I've only tested this on Linux with g++ 4.6.  It should work fine with any
version of GCC on Linux and Mac, as long as the g++ and gcov versions match
(otherwise you'll be spammed by a warning like "found version 406, expected
version 408").  Clang ostensibly should also work with the same --coverage
flags, though it also may need -lprofile_rt on the linker (and libprofile_rt to
be present on the system, which it seems is not currently the default case on
Goobuntu).

[borenet, 2013-09-12 17:22:58]

https://codereview.chromium.org/23523055/diff/1/gyp/common_conditions.gypi
File gyp/common_conditions.gypi (right):

https://codereview.chromium.org/23523055/diff/1/gyp/common_conditions.gypi#ne...
gyp/common_conditions.gypi:209: 'cflags': ['-g --coverage'],
We already provide '-g' in both Debug and Release... why do we need it again
here?

https://codereview.chromium.org/23523055/diff/1/tools/gcov_shim
File tools/gcov_shim (right):

https://codereview.chromium.org/23523055/diff/1/tools/gcov_shim#newcode9
tools/gcov_shim:9: if [[ $1 != "-a" && $1 != "-all-blocks" && $1 !=
"--all-blocks" ]]; then
I'd prefer $1 be in quotes even though it isn't strictly needed.

[mtklein, 2013-09-12 17:34:00]

https://codereview.chromium.org/23523055/diff/1/gyp/common_conditions.gypi
File gyp/common_conditions.gypi (right):

https://codereview.chromium.org/23523055/diff/1/gyp/common_conditions.gypi#ne...
gyp/common_conditions.gypi:209: 'cflags': ['-g --coverage'],
On 2013/09/12 17:22:58, borenet wrote:
> We already provide '-g' in both Debug and Release... why do we need it again
> here?

Yeah, I suppose debug symbols aren't necessary, but they don't really hurt
anything.  Is there some reason to leave them out?  I just added them for
symmetry with the other build targets.

https://codereview.chromium.org/23523055/diff/1/tools/gcov_shim
File tools/gcov_shim (right):

https://codereview.chromium.org/23523055/diff/1/tools/gcov_shim#newcode9
tools/gcov_shim:9: if [[ $1 != "-a" && $1 != "-all-blocks" && $1 !=
"--all-blocks" ]]; then
On 2013/09/12 17:22:58, borenet wrote:
> I'd prefer $1 be in quotes even though it isn't strictly needed.

Done.

[borenet, 2013-09-12 17:40:02]

LGTM

https://codereview.chromium.org/23523055/diff/1/gyp/common_conditions.gypi
File gyp/common_conditions.gypi (right):

https://codereview.chromium.org/23523055/diff/1/gyp/common_conditions.gypi#ne...
gyp/common_conditions.gypi:209: 'cflags': ['-g --coverage'],
On 2013/09/12 17:34:00, mtklein wrote:
> On 2013/09/12 17:22:58, borenet wrote:
> > We already provide '-g' in both Debug and Release... why do we need it again
> > here?
> 
> Yeah, I suppose debug symbols aren't necessary, but they don't really hurt
> anything.  Is there some reason to leave them out?  I just added them for
> symmetry with the other build targets.

Whoa - sorry, I totally missed that this was a different configuration.  This is
fine.

[tfarina, 2013-09-12 18:58:46]

nice! happy to see this being added.