[PATCH] D73307: Unique Names for Functions with Internal Linkage

[Sriraman Tallam via Phabricator via cfe-commits]

tmsriram added a comment.

We just noticed an issue with alias attribute and this option.  Here is the code that exposes the problem:

alias_global.c

static int foo;
extern int bar __attribute__((alias("foo")))

$ clang -c alias_global.c -funique-internal-linkage-names
alias_global.c:4:31: error: alias must point to a defined variable or function
extern int bar __attribute__((alias("foo")));

This happens because bar is aliased to "foo" and not "foo.<md5sum>".

I would like to know your thoughts on this?  Here is what I think.  alias attribute is a bit special in that the symbol name must be given carefully, for instance the mangled name if it is a C++ compile and the actual name for a C compile.  Even without the option, the same error will happen if a C++ compiler was used on this code.  So, in some sense, alias attribute requires the user to know what symbol name to expect.  -funique-internal-linkage-names can be treated as just an additional extension of this where the user must append the md5 hash of the module, which can be computed independently  with:

$ echo -n alias_global.c | md5sum

So, I suggest we leave it as it is and add to the documentation that this needs to be kept in mind.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D73307/new/

https://reviews.llvm.org/D73307