Multiple Issues with Attribute Alias

[Quuxplusone]

Bugzilla Link	PR13162
Status	NEW
Importance	P enhancement
Reported by	Reid Watson (reidw@google.com)
Reported on	2012-06-20 20:33:07 -0700
Last modified on	2018-10-25 20:11:52 -0700
Version	trunk
Hardware	PC Linux
CC	baldrick@free.fr, llvm-bugs@lists.llvm.org, rafael@espindo.la, richard-llvm@metafoo.co.uk
Fixed by commit(s)
Attachments	target.tar.gz (910 bytes, application/x-gzip)
Blocks
Blocked by
See also

Created attachment 8736
.tar.gz with five test cases and a perl script to compare output

As it stands, clang will accept a number of peculiar constructs related to
attribute alias on functions.
The idea that attribute alias is equivalent to a definition is not reflected in
the code base, so a number of obvious errors are not detected.

This includes cases such as
void foo() __attribute__((alias("bar"),alias("baz")))

I've attached a number of failing cases, along with an example of how defining
a method like

void foo() __attribute__((alias("bar"))){}

isn't detected and produces unpredictable results.

I've attached five such test cases, along with a perl script to compare the
diagnostics of clang and gcc.

[Quuxplusone]

Attached target.tar.gz (910 bytes, application/x-gzip): .tar.gz with five test cases and a perl script to compare output

[Quuxplusone]

Which gcc version did you test with?  While working on dragonegg I noticed that
gcc's behavior (eg what it considers an error) has been evolving.  Also, gcc
will
happily produce assembler that doesn't assemble, while LLVM rejects such
earlier.

[Quuxplusone]

(In reply to comment #1)
> Which gcc version did you test with?  While working on dragonegg I noticed
that
> gcc's behavior (eg what it considers an error) has been evolving.  Also, gcc
> will
> happily produce assembler that doesn't assemble, while LLVM rejects such
> earlier.

GCC 4.6.1 will reject all of the included test cases as erroneous
redefinitions, except for alias_and_body.c, which defines a function like:

void __attribute__((alias("target"))) foo() {puts("foo");}

GCC will compile this and execute the body of foo when run.