A C program that references external data via an 'extern' fails to link, when
the data is defined as thread-local in a separately compiled file, on an
x86_64 (Opteron, Fedora Core 5) platform.
For example,
==> file1.c <==
extern int x;
int main() {
x = 5;
}
==> file2.c <==
int __thread x = 10;
------
% gcc file2.c file1.c
/usr/bin/ld: x: TLS definition in /tmp/ccOzkuFX.o section .tdata mismatches
non-TLS reference in /tmp/cc1AhtnT.o
/tmp/cc1AhtnT.o: could not read symbols: Bad value
collect2: ld returned 1 exit status
------
The example will compile and link properly with the addition of __thread to
the extern declaration above.
IMO, the user should not have to specify __thread on the extern declaration
because the location of the data (section and relocation type) should be
defined only at the point the data item is declared.
Note that this example (without the additions of __thread) will compile and
link as is, on an IA64 platform.
(GNU ld version 2.16.91.0.6 20060212)
--
Summary: X86_64: thread-local access via extern requires __thread
Product: binutils
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: ld
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: gary at intrepid dot com
CC: bug-binutils at gnu dot org
GCC host triplet: x86_64-unknown-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=2870
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