http://llvm.org/bugs/show_bug.cgi?id=16901
Bug ID: 16901
Summary: attribute alias does not honor __thread specifier
Product: clang
Version: 3.3
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
Hello guys and ladies.
Clang 3.3 does not honor __thread specifier on an alias declaration.
How to reproduce it. First create 2 files (fileA.c and fileB.c):
====== fileA.c =========
__thread int x;
========================
====== fileB.c =========
extern __thread int y __attribute__((alias("x")));
int main(int argc, char **argv)
{
return y;
}
========================
Compile it:
clang fileA.c fileB.c
The error will be something like:
ld: x: TLS definition in /tmp/test1-HNs8cE.o section .tbss mismatches non-TLS
reference in /tmp/test2-A6WKVL.o
/tmp/test2-A6WKVL.o: could not read symbols: Bad value
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Some experiments:
If you remove BOTH __thread specifiers from the x definition in fileA.c and the
alias declaration in fileB.c, then everything will work, as clang does not
produce TLS variables.
If you remove the __thread specifier from the fileB.c, then THE RESULT WILL BE
THE SAME, thus I deduce that clang just ignores the specifier from the alias
declaration.
If you just resort to normal 'extern __thread int x' declaration in fileB.c,
then everything will work.
I suspect clang just ignores the __thread specifier in alias declarations.
I'm using clang 3.3 x86_64 compiled by gcc 4.7.1 under Slackware 14.0.
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