diff options
author | Rafael Espindola <rafael.espindola@gmail.com> | 2014-03-26 04:48:47 +0000 |
---|---|---|
committer | Rafael Espindola <rafael.espindola@gmail.com> | 2014-03-26 04:48:47 +0000 |
commit | 33845aa8c489e52e6287c75356daa8dd04b87350 (patch) | |
tree | bf3c0f7e8d86a434bbb77f630450b541239a1131 /docs/LangRef.rst | |
parent | 577708be42f58f7f3042bbab50537ecdea20acad (diff) | |
download | llvm-33845aa8c489e52e6287c75356daa8dd04b87350.tar.gz llvm-33845aa8c489e52e6287c75356daa8dd04b87350.tar.bz2 llvm-33845aa8c489e52e6287c75356daa8dd04b87350.tar.xz |
Prevent alias from pointing to weak aliases.
Aliases are just another name for a position in a file. As such, the
regular symbol resolutions are not applied. For example, given
define void @my_func() {
ret void
}
@my_alias = alias weak void ()* @my_func
@my_alias2 = alias void ()* @my_alias
We produce without this patch:
.weak my_alias
my_alias = my_func
.globl my_alias2
my_alias2 = my_alias
That is, in the resulting ELF file my_alias, my_func and my_alias are
just 3 names pointing to offset 0 of .text. That is *not* the
semantics of IR linking. For example, linking in a
@my_alias = alias void ()* @other_func
would require the strong my_alias to override the weak one and
my_alias2 would end up pointing to other_func.
There is no way to represent that with aliases being just another
name, so the best solution seems to be to just disallow it, converting
a miscompile into an error.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204781 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/LangRef.rst')
-rw-r--r-- | docs/LangRef.rst | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/docs/LangRef.rst b/docs/LangRef.rst index c959f56ef1..b0b8bfebee 100644 --- a/docs/LangRef.rst +++ b/docs/LangRef.rst @@ -681,6 +681,10 @@ the aliasee. The aliasee must be a definition. +Aliases are not allowed to point to aliases with linkages that can be +overridden. Since they are only a second name, the possibility of the +intermediate alias being overridden cannot be represented in an object file. + .. _namedmetadatastructure: Named Metadata |