[Bug 1711337] Re: Firefox crashes at start on armv7L after 55.0.1 update

[James Donald]

Ugh, yeah doing some simple helloworld tests confirms these are armhf
gcc *defaults*.

> it's what *defines* armhf as armhf.

Defines: This appears true for -march=armv7-a -mfloat-abi=hard. As for
-mfpu, adding -mfpu=neon results in some assembly differences, namely
using register d16 and above.

> Unless something is explicitly setting those things differently

The Firefox build log has some instances of -mfpu=neon, particularly in
Skia. However, Chromium does as well so indeed this is a longshot.

Looks like we're back to the drawing board. Still some hope with changes
like building Skia using clang, adding -mthumb, or -fstack-protector-
strong, but none of these other differences stand out as something
present in both the Chromium and Arch Linux builds.

I think I misunderstood earlier about the intent of looking at Firefox
57's about:buildconfig. As that's technically still a Skia-broken build,
we can continue to examine that configuration for other differences vs
the Arch Linux one.

> [herrtimson] If there's a chance to get the output of
about:buildconfig regardless the segfault at startup, I'm all eager to
learn about this.

With broken browsers like Firefox 58 and 59 armhf, find the build config
like so:

strings /usr/lib/firefox/omni.ja | grep -A 31 "Built from"

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Title:
  Firefox crashes at start on armv7L after 55.0.1 update

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