[MinGW-notify] [ mingw-Bugs-2837047 ] [gcc-4.4.0] __thread not producing thread-specific storage

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Bugs item #2837047, was opened at 2009-08-13 10:59
Message generated for change (Comment added) made by earnie
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Category: gcc
Group: Aged issue
>Status: Closed
>Resolution: Out of Date
Priority: 5
Private: No
Submitted By: Peter Hurley (peterjhurley)
Assigned to: Earnie Boyd (earnie)
Summary: [gcc-4.4.0] __thread not producing thread-specific storage

Initial Comment:
gcc-4.4.0-mingw is not producing thread-specific storage when __thread specifier is used.

In the submission source file, a number of threads are created that increment a __thread variable.  When all threads have terminated, the "master" thread (original process thread) prints "its" __thread variable to stdout.  In the test case, it is non-zero (should be zero since original process thread does not run that code).

-- Details --
Generate tls.exe (test program) with any of the following:
g++ -o tls.exe tls.cpp
g++ -mthreads -o tls.exe tls.cpp
g++ -shared-libgcc -o tls.exe tls.cpp
... etc ...

Compilation generates reference to __emutls_get_address which just returns the same memory address for each thread.

[Build environment]
WinXP Pro SP3
intel harpertown
gcc-4.4.0-mingw32
binutils-2.19.1
w32api-3.13
mingwrt-3.15.2

FYI - Unfortunately, this means that multi-threaded exception handling is broken too (which is how I stumbled onto this).


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>Comment By: Earnie Boyd (earnie)
Date: 2012-11-09 12:19

Message:
As far as I can tell the attached test is working.  The main returns 0 for
tls_value.

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Comment By: Earnie Boyd (earnie)
Date: 2012-08-03 12:24

Message:
See also
https://sourceforge.net/tracker/?func=detail&aid=3322937&group_id=2435&atid=102435

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Comment By: Earnie Boyd (earnie)
Date: 2012-06-14 06:58

Message:
This sounds familiar to another issue.  Assigning to Chris for follow up.

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Comment By: Peter Hurley (peterhurley)
Date: 2012-04-17 09:58

Message:
I have no idea if this bug still exists in mingw.  The fact that it's still
an open item and includes a test case to validate whether it still exists
would seem to indicate that the defect remains.

@dovgaluk
The value of tls_value for every thread but the main process thread should
be 1. The value of the main process thread should be 0.  Regardless, your
modification is not stable since the standard library is not required to be
thread-safe.

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Comment By: Pavel Dovgalyuk (dovgaluk)
Date: 2012-04-13 03:38

Message:
This bug does not seem to be fixed in 4.6.2.
Proveded tls.cpp works correctly, but when I alter thread_fn as follows it
print equal for several threads:

unsigned __stdcall thread_fn(void*)
{
	++tls_value;
	std::cout << &tls_value << "\n";
	return 0;
}

Number of threads (const unsigned processors) was set to 16, which is
greater than the number of physical cores.

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Comment By: Peter Hurley (peterhurley)
Date: 2010-06-28 08:12

Message:
This is probably fixed with the new gcc 4.5.0 release.  I saw some dev
traffic about this back in Jan-Feb '10 on the mailing list - you should ask
there.  I seriously doubt a fix will every be backported.

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Comment By: Mario Maya (mmaya)
Date: 2010-06-24 04:54

Message:
Any alternative other than linking libgcc statically? It show me an error
at the end of the program (destroying static variables)...

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Comment By: Jonathan Liu (net147)
Date: 2010-01-01 17:37

Message:
If the compiler doesn't have shared libraries enabled (as with the
previously mentioned compilers) or compiling with -static-libgcc option,
the test case seems to run fine.

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Comment By: Jonathan Liu (net147)
Date: 2009-12-29 02:35

Message:
Works with the following compilers using -mthreads option:
-MinGW GCC 4.4.1 TDM-2
-Equation Solution GCC 4.4.2 32-bit

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