[PATCH] D142888: [compiler-rt] Fix build on ARM

Mon Jan 30 06:25:29 PST 2023

luporl added a comment.

In D142888#4090559 <https://reviews.llvm.org/D142888#4090559>, @DavidSpickett wrote:

> I would split this into 2 commits, where one is the triple fix. You can copy the relevant bit of the description as well. There is some thinking behind that change that should be preserved in it's own commit.
>
> Then this can be "Fix building GWPASAN on ARM". Also include in the commit message the cmake command that was broken. Just because it's useful to see exactly what config was fixed, when looking back. They can get pretty specific, and it lets people compare their usage against a known good command.

Right, it makes sense, thanks for the quick review.

> Last time we fixed something like this was https://reviews.llvm.org/D131250 for scudo. I'm a bit confused to not see that change in this file too. Diana guessed at the time the cause was passing `unwindlib=none` and now we're adding it back to fix a similar issue.
>
> The option `COMPILER_RT_USE_LLVM_UNWINDER` also adds `--unwindlib=None`, does that have the same effect as this change? I'm trying to understand if whatever unwind lib you get without this change, should be providing `__aeabi_unwind_cpp_pr*` or not. And exactly which unwind lib we attempt to use in each scenario.

The cause of the issue was really passing `unwindlib=none` to the link command. In this case the unwind lib must be explicitly passed. It seems I took a different approach to fix it, that was removing `unwindlib=none` for ARM, when GwpAsan is enabled.
I don't know if both have the same effect or which one is better. I'll dig a bit further.

Repository:
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  https://reviews.llvm.org/D142888/new/

https://reviews.llvm.org/D142888