[rust-dev] Impact of -ftrapv on Firefox

Robert O'Callahan robert at ocallahan.org
Mon Jan 13 17:19:25 PST 2014


On Tue, Jan 14, 2014 at 12:11 PM, Daniel Micay <danielmicay at gmail.com>wrote:

> There's also the issue that libgcc_s is missing the function LLVM will
> generate for 64-bit overflow checked multiplication on most
> architectures. It's there on x86_64, but on x86 you'll need a `clang`
> set up to use `compiler-rt`.
>
> It's hilarious that `gcc` is totally broken though...
>

Thanks for catching that. My experiments indicate that -ftrapv works in gcc
for x86 but not x86-64. Which explains why the Firefox try builds only work
for x86-64. Which makes sense, since Firefox contains code that would
depend on overflow wrapping around.

So we're back to not knowing anything :-).

Rob
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