Introduce a V8_NORETURN macro and use it to make GCC 4.9.2 happy again.

Introduce a V8_NORETURN macro and use it to make GCC 4.9.2 happy again.

Without that, it has a few false positives about out-of-bounds array accesses.
Also makes the clang static-analyzer happy.

Original code review from Sven Panne:
https://codereview.chromium.org/790723002/

Committed: https://crrev.com/0b48b2a8ebfc791a36f4ec1f299f46db76265a3a
Cr-Commit-Position: refs/heads/master@{#30977}

[skomski, 2015-09-24 17:51:40]

karl@skomski.com changed reviewers:
+ bmeurer@chromium.org

[skomski, 2015-09-24 17:52:46]

PTAL

[Benedikt Meurer, 2015-09-24 17:57:39]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-09-24 17:57:39]

lgtm

[commit-bot: I haz the power, 2015-09-24 17:57:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361763004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361763004/1

[commit-bot: I haz the power, 2015-09-24 18:07:04]

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

[commit-bot: I haz the power, 2015-09-24 18:07:05]

Try jobs failed on following builders:
  v8_linux_gcc_compile_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_gcc_compile_rel/bu...)

[skomski, 2015-09-25 09:30:24]

Since voiding UNIMPLEMENTED (https://codereview.chromium.org/1371593003/) was
rejected.

This will still fail in gcc:
https://chromium.googlesource.com/v8/v8.git/+/master/src/elements.cc#254.
gcc fails on this line because the introduced `noreturn` leads to a optimization
that leads to a false positive warning about overflow.
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_gcc_compile_rel/bu...

I changed it to UNREACHABLE() // TODO(danno): implement? This would follow the
recommendation by Jakob to remove FATAL out of loops.
This would also help clang as mentioned.

[Jakob Kummerow, 2015-09-25 12:27:42]

jkummerow@chromium.org changed reviewers:
+ jkummerow@chromium.org

[Jakob Kummerow, 2015-09-25 12:27:42]

No, simply removing the check was not at all what I meant. Replacing
UNIMPLEMENTED with UNREACHABLE obviously has the same effect as voiding
UNIMPLEMENTED, and therefore is just as undesirable.

The way to fix such cases is to *move* the check out of the loop. In the
specific case at hand, it can be dropped entirely, see
https://codereview.chromium.org/1372533002.

https://codereview.chromium.org/1361763004/diff/20001/src/elements.cc
File src/elements.cc (right):

https://codereview.chromium.org/1361763004/diff/20001/src/elements.cc#newcode257
src/elements.cc:257: UNREACHABLE();  // TODO(danno): implement
Nope.

[skomski, 2015-09-25 12:35:10]

Patchset #2 (id:20001) has been deleted

[skomski, 2015-09-25 12:41:28]

On 2015/09/25 12:27:42, Jakob wrote:
> No, simply removing the check was not at all what I meant. Replacing
> UNIMPLEMENTED with UNREACHABLE obviously has the same effect as voiding
> UNIMPLEMENTED, and therefore is just as undesirable.
> 
> The way to fix such cases is to *move* the check out of the loop. In the
> specific case at hand, it can be dropped entirely, see
> https://codereview.chromium.org/1372533002.
> 
> https://codereview.chromium.org/1361763004/diff/20001/src/elements.cc
> File src/elements.cc (right):
> 
>
https://codereview.chromium.org/1361763004/diff/20001/src/elements.cc#newcode257
> src/elements.cc:257: UNREACHABLE();  // TODO(danno): implement
> Nope.

Yeah sorry removed the patchset.

[skomski, 2015-09-25 12:41:34]

The CQ bit was checked by karl@skomski.com

[commit-bot: I haz the power, 2015-09-25 12:41:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361763004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361763004/1

[commit-bot: I haz the power, 2015-09-25 12:55:56]

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

[commit-bot: I haz the power, 2015-09-25 12:55:57]

Try jobs failed on following builders:
  v8_linux_gcc_compile_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_gcc_compile_rel/bu...)

[skomski, 2015-09-25 21:24:01]

On 2015/09/25 12:55:57, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   v8_linux_gcc_compile_rel on tryserver.v8 (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_gcc_compile_rel/bu...)

PTAL
Updated to fix:

.././src/heap/spaces-inl.h: In function ‘void
v8::internal::TestRegress169928()’:
.././src/heap/spaces-inl.h:449:3: error: assuming signed overflow does not occur
when assuming that (X - c) > X is always false [-Werror=strict-overflow]
   if (allocation_info_.limit() - top < size_in_bytes) {

[skomski, 2015-09-26 11:21:36]

Patchset #2 (id:40001) has been deleted

[skomski, 2015-09-26 11:21:40]

The CQ bit was checked by karl@skomski.com

[commit-bot: I haz the power, 2015-09-26 11:21:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361763004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361763004/1

[commit-bot: I haz the power, 2015-09-26 11:37:54]

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

[commit-bot: I haz the power, 2015-09-26 11:37:55]

Try jobs failed on following builders:
  v8_linux_gcc_compile_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_gcc_compile_rel/bu...)

[skomski, 2015-09-26 18:24:33]

The CQ bit was checked by karl@skomski.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-26 18:24:39]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361763004/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361763004/60001

[commit-bot: I haz the power, 2015-09-26 18:32:58]

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

[commit-bot: I haz the power, 2015-09-26 18:32:59]

Dry run: Try jobs failed on following builders:
  v8_win_compile_dbg on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win_compile_dbg/builds/7991)

[skomski, 2015-09-26 19:11:43]

The CQ bit was checked by karl@skomski.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-26 19:11:50]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361763004/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361763004/80001

[commit-bot: I haz the power, 2015-09-26 19:35:10]

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

[commit-bot: I haz the power, 2015-09-26 19:35:11]

Dry run: This issue passed the CQ dry run.

[skomski, 2015-09-26 21:01:31]

karl@skomski.com changed reviewers:
+ jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-09-28 11:31:17]

lgtm

[skomski, 2015-09-28 13:38:03]

The CQ bit was checked by karl@skomski.com

[skomski, 2015-09-28 13:38:04]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/1361763004/#ps80001
(title: "gcc 4.8 doesn't understand #pragma ignored")

[commit-bot: I haz the power, 2015-09-28 13:38:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361763004/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361763004/80001

[commit-bot: I haz the power, 2015-09-28 14:02:58]

Committed patchset #3 (id:80001)

[commit-bot: I haz the power, 2015-09-28 14:03:18]

Patchset 3 (id:??) landed as
https://crrev.com/0b48b2a8ebfc791a36f4ec1f299f46db76265a3a
Cr-Commit-Position: refs/heads/master@{#30977}

[Igor Sheludko, 2015-09-28 16:40:27]

A revert of this CL (patchset #3 id:80001) has been created in
https://codereview.chromium.org/1370203002/ by ishell@chromium.org.

The reason for reverting is: This CL breaks cross-compiling to arm..