Allocator shim explanatory error message.

Allocator shim explanatory error message.

Error message explicitly tells to disable allocator shim if libc
is unsupported. Currently it's hardly achievable to figure out
target libc implementation on the GN generation stage.

BUG=595406
Committed: https://crrev.com/045df297e953e60f953710e4266205729050e1cf
Cr-Commit-Position: refs/heads/master@{#423516}

[kraynov, 2016-10-06 11:55:45]

The CQ bit was checked by kraynov@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-06 11:55:51]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[kraynov, 2016-10-06 12:05:08]

kraynov@chromium.org changed reviewers:
+ primiano@chromium.org, smcgruer@google.com

[kraynov, 2016-10-06 12:05:09]

That's all reasonable we can do regarding this issue crbug.com/595406

Reasons:
1. 'embedded' GN arg wasn't moved from GYP. //base/config/BUILDCONFIG.gn
explains that any unnecessary global flags are unwelcome. So we can't disable
allocator shim by 'embedded' flag.
2. GN has ability to dynamically generate GN definitions via exec_script()
function, but it has high cost and unable to compile something before execution
natively via GN. Hacks with compiler invocation apart of GN is not an option.

So we have quite few platforms using Linux without Glibc and this error message
will provide actionable advice to adjust GN args.

[commit-bot: I haz the power, 2016-10-06 12:10:33]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-06 12:10:34]

Dry run: Try jobs failed on following builders:
  chromeos_daisy_chromium_compile_only_ng on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_daisy_...)

[kraynov, 2016-10-06 12:57:25]

The CQ bit was checked by kraynov@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-06 12:57:34]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Primiano Tucci (use gerrit), 2016-10-06 13:08:32]

Ok I see, your reasoning makes sense.
LGTM to improve the comment and make it more actionable. Will reach out to the
original folks and ask how are they dealing with GN now.

https://codereview.chromium.org/2393413003/diff/1/base/allocator/allocator_sh...
File base/allocator/allocator_shim_override_glibc_weak_symbols.h (right):

https://codereview.chromium.org/2393413003/diff/1/base/allocator/allocator_sh...
base/allocator/allocator_shim_override_glibc_weak_symbols.h:109: has no idea how
to support target's libc. Please disable this feature \
I'd keep it shorter and just say:
"The target platform does not seem to use Glibc. Disable the allocator shim by
setting 'use_experimental_allocator_shim=false' in GN args."

[commit-bot: I haz the power, 2016-10-06 13:10:01]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-06 13:10:02]

Dry run: Try jobs failed on following builders:
  chromeos_x86-generic_chromium_compile_only_ng on
master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_x86-ge...)

[kraynov, 2016-10-06 13:26:23]

The CQ bit was checked by kraynov@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-06 13:26:33]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-06 13:57:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-06 13:58:01]

Dry run: This issue passed the CQ dry run.

[kraynov, 2016-10-06 14:01:30]

The CQ bit was checked by kraynov@chromium.org

[kraynov, 2016-10-06 14:01:30]

The patchset sent to the CQ was uploaded after l-g-t-m from
primiano@chromium.org
Link to the patchset: https://codereview.chromium.org/2393413003/#ps30001
(title: "wording")

[commit-bot: I haz the power, 2016-10-06 14:02:09]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-06 14:07:10]

Committed patchset #3 (id:30001)

[commit-bot: I haz the power, 2016-10-06 14:09:08]

Description was changed from

==========
Allocator shim explanatory error message.

Error message explicitly tells to disable allocator shim if libc
is unsupported. Currently it's hardly achievable to figure out
target libc implementation on the GN generation stage.

BUG=595406
==========

to

==========
Allocator shim explanatory error message.

Error message explicitly tells to disable allocator shim if libc
is unsupported. Currently it's hardly achievable to figure out
target libc implementation on the GN generation stage.

BUG=595406

Committed: https://crrev.com/045df297e953e60f953710e4266205729050e1cf
Cr-Commit-Position: refs/heads/master@{#423516}
==========

[commit-bot: I haz the power, 2016-10-06 14:09:09]

Patchset 3 (id:??) landed as
https://crrev.com/045df297e953e60f953710e4266205729050e1cf
Cr-Commit-Position: refs/heads/master@{#423516}