Note:
=====
1. In M-73, this crash is seen on Mac OS
2. Presently this crash is ranked as top #1 in "app_shim" process with 12 instances from 11 clients.
3. This issue is regressed recently in M73
4. List of builds
   73.0.3642.0	20.00%	4
   73.0.3641.0	5.00%	1
   73.0.3640.0	5.00%	1
   73.0.3639.1	60.00%	12
   73.0.3639.0	5.00%	1
   73.0.3638.0	5.00%	1

Suspected Range: https://chromium.googlesource.com/chromium/src/+log/72.0.3626.0..73.0.3639.0?pretty=fuller&n=10000

Unable to pin point to that exact experiment that could have caused this spike hence putting this into sheriff's queue for inputs.

[stability sheriff] I'm not familiar with the app_shim process. ccameron could you look? There are some changes in the blame list like:

https://chromium-review.googlesource.com/c/1364220
https://chromium-review.googlesource.com/c/1364210
https://chromium-review.googlesource.com/c/1359724
https://chromium-review.googlesource.com/c/1373433
https://chromium-review.googlesource.com/c/1373733

NamedPlatformChannel::ConnectToServer can fail and return an invalid endpoint. You probably just need to handle that gracefully.

+ellyjones to triage and find an owner

to sdy@ - I think from the stack trace that this is a PWA bug? Not R-V-EI though.

[stability sheriff]

sdy@: could you please confirm if you are the right owner for this bug?

I don't know what this crash is off the top of my head, but I can look at it.

Please see comment #3. At least when I last looked, the crash seemed clearly due to an invalid handle being passed to SendInvitation, which is not allowed. The invalid handle was acquired (or rather... not acquired) by making an unsuccessful call to NamedPlatformChannel::ConnectToServer in the shim code.

Thanks! I missed that comment before.

[stability sheriff]

Thanks for looking into this. Removing this bug from the stability sheriff queue.

I think I found the root cause of this, and it's a horrible bug that I'm surprised we hadn't hit before.

Note that in app_shim_loader at [0], we populate app_mode::ChromeAppModeInfo. This is in code that is compiled directly into app_shim_loader.

Then at [1] we read the app_mode::ChromeAppModeInfo and parse it.

The idea is that app_mode::ChromeAppModeInfo is stable across versions. The problem is that it *IS NOT*. It includes such things as std::string (not stable) and base::FilePath (totally not stable!).

The result is that when I try to run a shim, the app_mode::ChromeAppModeInfo is garbage and I get the error spew:

  ccameron-macbookpro:Chrome Canary Apps.localized ccameron$ ./Killer\ Marmot.app/Contents/MacOS/app_mode_loader 
  [0121/015456.736026:FATAL:double_fork_and_exec.cc(126)] execvp /Users/ccameron/Applications/Chrome Canary Apps.localized/Killer Marmot.app/Helpers/crashpad_handler: No such file or directory (2)
  [0121/015456.736702:ERROR:file_io.cc(89)] ReadExactly: expected 8, observed 0
  [0121/015456.737642:WARNING:resource_bundle.cc(357)] locale_file_path.empty() for locale en_US
  [0121/015457.013714:WARNING:resource_bundle.cc(922)] locale resources are not loaded
  [0121/015457.017747:ERROR:named_platform_channel_posix.cc(145)] connect App Shim Socket: No such file or directory (2)
  Trace/BPT trap: 5

This is not a fun bug to discover on the week of branch, but it is totally fix-able (just use types that are *actually* stable).

All shims that ever were created need to be regenerated (but hey, they're already all broken ... probably by the completely innocuous crrev.com/620036 (just a guess, could have been a toolchain update).

[0] https://cs.chromium.org/chromium/src/chrome/app_shim/app_mode_loader_mac.mm?rcl=58acb7411fa06ff319f01e21fdadd6b3ea538cca&l=200
[1] https://cs.chromium.org/chromium/src/chrome/app_shim/chrome_main_app_mode_mac.mm?rcl=58acb7411fa06ff319f01e21fdadd6b3ea538cca&l=168

I think we have run into exactly this bug before in  Issue 561205 , which was caused from moving from the system C++ stdlib (a GNU variant) to a statically linked libc++.

Hopefully the same fix from then will work now - bumping the versioned name of the method looked up in the Chromium framework by the shim, which will cause the shim to fail to find the entry point, and be recreated. :)

The fix from  issue 561205  won't help here. We now statically link not system libc++, but one that's explicitly built with _LIBCPP_ABI_UNSTABLE -- C++ abi types can change more or less at any point now.

If we had done the right fix back in  issue 561205  (mentioned in comment 11), we wouldn't have this replay now :-/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9ba5da35aa4601b8e3f13b2028a09cc516d463e3

commit 9ba5da35aa4601b8e3f13b2028a09cc516d463e3
Author: Christopher Cameron <ccameron@chromium.org>
Date: Tue Jan 22 22:00:56 2019

MacPWAs: Make ChromeAppModeInfo stable

This structure is to be shared across separately-compiled versions of
Chrome, since it is shared between the app_mode_loader and Chrome.

The structures std::string and base::FilePath are not stable, so don't
use them. Increment the app version number to reflect this change.

Add compile-time checks that will indicate if the structure size
changes.

Version mismatches were manifesting as a crash in mojo::SendInvitation
the mojo::ScopedMessagePipeHandle was invalid. Add a CHECK that the
handle is valid for controlled demolition.

Bug: 916034
Change-Id: If06a590b8a28bc9ea9d8c2470a49a2fc4111c93b
Reviewed-on: https://chromium-review.googlesource.com/c/1425038
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624947}
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/app/framework.order
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/app_shim/app_mode_loader_mac.mm
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/app_shim/app_shim_controller.mm
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/app_shim/chrome_main_app_mode_mac.mm
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/browser/apps/platform_apps/shortcut_manager.cc
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/common/mac/app_mode_common.h
[modify] https://crrev.com/9ba5da35aa4601b8e3f13b2028a09cc516d463e3/chrome/common/mac/app_mode_common.mm