[Bug libgomp/42829] New: TLS detection in ./configure is wrong.

[Bug libgomp/42829] New: TLS detection in ./configure is wrong.

[jos dot de_laender at telenet dot be]

In attachment, you find the code that is used inside the configure m4 macro for
detecting the presence of TLS.

This check is unreliable.

When compiled with -O2 (as done in configure) the result might be that the
compiler reports same adress due to optimization and decides there is no TLS.

When compiled with -O0, it yields the correct result.

This is an optimization artefact. Please extend the test with the two lines I
put in comment. This way the test succeeds correctly, even after optimization.


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           Summary: TLS detection in ./configure is wrong.
           Product: gcc
           Version: 4.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgomp
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jos dot de_laender at telenet dot be
  GCC host triplet: i686-pc-mingw32
GCC target triplet: mingw64 - see description.


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829

[Bug libgomp/42829] TLS detection in ./configure is wrong.

[jos dot de_laender at telenet dot be]

------- Comment #1 from jos dot de_laender at telenet dot be  2010-01-21 15:42 -------
Created an attachment (id=19681)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19681&action=view)
The test.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829

[Bug libgomp/42829] TLS detection in ./configure is wrong.

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2010-01-21 19:48 -------
Oh this test should pass no matter what really as TLS is emulated on mingw via
functions which call pthreads.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829

[Bug libgomp/42829] TLS detection in ./configure is wrong.

[jakub at gcc dot gnu dot org]

------- Comment #3 from jakub at gcc dot gnu dot org  2010-01-21 20:37 -------
Yeah, the test is certainly fine, if it sporadically fails, there are issues
with the mingw TLS or thread implementation (or both).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829

[Bug libgomp/42829] TLS detection in ./configure is wrong.

[jos dot de_laender at telenet dot be]

------- Comment #4 from jos dot de_laender at telenet dot be  2010-01-21 22:14 -------
Your call.
I *don't* think it's fine.
Even if there *is* TLS, it can fail due to the -O2 optimizing.
(it doesn't detect the referring via &).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829

[Bug libgomp/42829] TLS detection in ./configure is wrong.

[ktietz at gcc dot gnu dot org]

------- Comment #5 from ktietz at gcc dot gnu dot org  2010-01-23 10:35 -------
Yes, I can confirm this issue, but want to investigate where the underlying
issue really comes from. The interesting issue I found is, that if a
TLS-variable isn't assigned, the values of the addresses in different threads
are equal. As soon as one thread initialize the variable in program flow (not
by initializing the global __thread variable), everthing works as expected.

Kai


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ktietz at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ktietz at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829

[Bug libgomp/42829] TLS detection in ./configure is wrong.

[iains at gcc dot gnu dot org]

------- Comment #6 from iains at gcc dot gnu dot org  2010-06-11 08:37 -------
closing as fixed by r160457 (trunk) and r160526 (4.5 release branch)


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iains at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42829