[PATCH] D155894: [BPF] allow external calls

Yonghong Song via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Jul 28 16:47:45 PDT 2023


yonghong-song added a comment.

> I'll abandon this, but it may be worthwhile to implement BPF-implies-fno-builtin *in clang*, if possible.

Thanks @tamird Indeed -fno-builtin or attribute no-builtin can fix the issue. But I think we should not put no-builtin as default since based on my experiment a lot of users using memset with a known constant size, expecting the compiler will transform it into a load, and we do not want to break such use cases. But we could advise users to use -fno-builtin or no-builtin attribute if their usage of memset involves a unknown size to a very large known size. This way, we can keep the fail message here since survival of builtin memset func means bpftool linking cannot resolve it.


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