[PATCH] D143803: [clang][alias|ifunc]: Add a diagnostic for mangled names

[Erich Keane via Phabricator via cfe-commits]

erichkeane added a comment.

In D143803#4154736 <https://reviews.llvm.org/D143803#4154736>, @0xdc03 wrote:

> Okay, I have now modified the diagnostic to look something like (as per the discussion at https://discord.com/channels/636084430946959380/636732781086638081/1079356357024694363):
>
>   ../../bug/ifunc-#59164.cpp:17:16: error: ifunc must point to a defined function
>   __attribute__((ifunc("resolver")))
>                  ^
>   ../../bug/ifunc-#59164.cpp:17:16: note: the name specified in an ifunc must refer to the mangled name
>   ../../bug/ifunc-#59164.cpp:17:16: note: function by that name is mangled as "_ZL8resolverv"
>   __attribute__((ifunc("resolver")))
>                  ^~~~~~~~~~~~~~~~~
>                  ifunc("_ZL8resolverv")
>   ../../bug/ifunc-#59164.cpp:20:16: error: alias must point to a defined variable or function
>   __attribute__((alias("resolver")))
>                  ^
>   ../../bug/ifunc-#59164.cpp:20:16: note: the name specified in an alias must refer to the mangled name
>   ../../bug/ifunc-#59164.cpp:20:16: note: function by that name is mangled as "_ZL8resolverv"
>   __attribute__((alias("resolver")))
>                  ^~~~~~~~~~~~~~~~~
>                  alias("_ZL8resolverv")
>   ../../bug/ifunc-#59164.cpp:23:24: error: ifunc must point to a defined function
>   __attribute__((unused, ifunc("resolver"), deprecated("hahahaha, isn't C great?"))) void func();
>                          ^
>   ../../bug/ifunc-#59164.cpp:23:24: note: the name specified in an ifunc must refer to the mangled name
>   ../../bug/ifunc-#59164.cpp:23:24: note: function by that name is mangled as "_ZL8resolverv"
>   __attribute__((unused, ifunc("resolver"), deprecated("hahahaha, isn't C great?"))) void func();
>                          ^~~~~~~~~~~~~~~~~
>                          ifunc("_ZL8resolverv")
>   3 errors generated.
>
> However, `clang/test/SemaCXX/externc-ifunc-resolver.cpp` still fails, and I am not entirely sure what to do with it. Should I update it to check the diagnostic? Also, it seems that the code I wrote prints "must refer to the mangled name" everywhere, even when the resolver or aliasee is not a function. Should I try to fix this? Or is it OK as it is?

I think updating that test with this additional note is the right thing to do.  As far as that note, saying 'mangled name' is perhaps not correct there, since what we really care is that it is the name-as-emitted to the linker. I don't have an idea on exactly what to call it.  If we could come up with a better phrase, it probably makes the diagnostic on the thing not being a function.

ALSO, it would be worth updating the error here to mention that it must point to a defined function, <x, y, Z> (where x,y,z are the things that it is allowed to target).


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