[clang] Diagnose problematic uses of constructor/destructor attribute (PR #67360)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> With regard to arguments: I know that the [FreeBSD runtime linker](https://github.com/freebsd/freebsd-src/blob/d06328c37bbcf3d3d3c7601372d29237996a6f6a/libexec/rtld-elf/aarch64/rtld_machdep.h#L59) (and according to https://stackoverflow.com/a/46331112 also glibc) passes argc, argv, envv to the constructor functions, so maybe that specific signature should be permitted?

Thank you for pointing this out!

That is an undocumented behavior of the attribute that I think only happens to work if the stars line up correctly. As I understand things, glibc does this, but musl does not and it seems MSVC CRT does something entirely different as well. Because we don't know which CRT will be loaded at runtime, it seems pretty dangerous to allow that behavior. We could maybe presume glibc on ELF targets, but it seems like a lot of security risk to support an undocumented use case. Do you know if this is documented somewhere and I'm just not seeing it? Any ideas on how we can add safety rails instead of allowing the signature and hoping for the best?

https://github.com/llvm/llvm-project/pull/67360