For tests such as https://searchfox.org/mozilla-central/rev/49cc27555d5b7ed2eb06baf156693dd578daa06f/toolkit/crashreporter/test/win64UnwindInfoTests.asm#262 the caller must ensure enough stack space in committed. This is done in: https://searchfox.org/mozilla-central/rev/49cc27555d5b7ed2eb06baf156693dd578daa06f/toolkit/crashreporter/test/nsTestCrasher.cpp#113 Here, the code is being optimized away by clang; mozilla::Unused is not enough. Working on a patch now to ensure we commit this stack space.

Great find!

Comment on attachment 8962715 [details] Bug 1449131: Ensure stack memory is being committed for use in win64 unwind CFI tests; https://reviewboard.mozilla.org/r/231584/#review237116 ::: toolkit/crashreporter/test/nsTestCrasher.cpp:116 (Diff revision 1) > } > > -void ReserveStack() { > - // This ensures our tests have enough reserved stack space. > - uint8_t* p = (uint8_t*)alloca(1024000); > - // This ensures we don't optimized away this meaningless code at build time. > +// This ensures tests have enough committed stack space. > +// Must not be inlined, or the stack space would not be freed for the caller > +// to use. > +void MOZ_HAVE_NEVER_INLINE ReserveStack() { This should be MOZ_NEVER_INLINE. The _HAVE_ stuff is just for use by the header's internal ifdef logic. Let's chat if that didn't work for some reason.

Pushed by ryanvm@gmail.com: https://hg.mozilla.org/integration/autoland/rev/e0e2463d86c6 Ensure stack memory is being committed for use in win64 unwind CFI tests; r=dmajor