Bug 39959 – exitStatus() returns 0 when child process crashes due to missing symbol in dylib

• Status: NEW
• Component: Tools / Tests

[David Kilzer (:ddkilzer)]

* SUMMARY
When an app crashes on Mac OS X 10.6 due to a missing symbol in a dylib (for example, testapi in run-javascriptcore-tests), the exitStatus() method in webkitdirs.pm returns 0 (zero) because the value passed in is 5.  This happens because WEXITSTATUS() does an 8-bit right shift of the value passed to it, which causes 5 to become 0.

Normally the 8-bit shift is the correct action since the exit status of the child process is stored in the upper 8 bits of $?.  However, when an app crashes due to a missing symbol in a dylib, $? is set to 5 and there is no child exit status.

Unfortunately, I haven't found any Perl man pages that fully describe what the lower 8 bits of $? are ("man perlvar" describes some, but not all, of the lower bits), so it's not clear how best to fix this.  Changing every place that calls exitStatus() to also check $? seems burdensome.

It would be nice if exitStatus() would always return a non-zero value if a non-zero value was passed in, even if it was less than 256.  I'm not sure if that would break other platforms, though.

[Mark Rowe (bdash)]

Some bits of $? represent the manner in which the process exited, which can be queried using WIFEXITED / WIFSIGNALED / WIFSTOPPED/.  Depending on the values of those macros you can use one of the following to learn more: WEXITSTATUS / WTERMSIG / WCOREDUMP / WSTOPSIG.

I’m not entirely sure what the combination of flags will be when an application fails to launch due to missing symbols, but I suspect it’s detectable via some combination of the above.  It may just be a matter of ensuring that WIFEXITED is true.