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IDProjectCategoryView StatusDate SubmittedLast Update
0010710CMakeModulespublic2010-05-13 19:112016-06-10 14:31
ReporterDaniel Richard G. 
Assigned ToBill Hoffman 
PrioritynormalSeveritymajorReproducibilityalways
StatusclosedResolutionmoved 
PlatformOSOS Version
Product VersionCMake-2-8 
Target VersionFixed in Version 
Summary0010710: FindThreads.cmake does not work properly on Tru64
Descriptionfind_package(Threads) in CMake 2.8.1 does not work correctly on OSF/Tru64. There are multiple problems with the module as it is currently written:

1. At line 141, there is a platform-specific conditional (CMAKE_SYSTEM MATCHES "OSF1-V*") that blanks out the name of the pthread library. This is not correct for my particular system; without a threading directive passed to the compiler, code fails to link due to missing pthread functions.

2. Prior to that point, the module does find -lpthread. But this is not the correct directive to use, according to the cc(1) man page: it's -pthread. (Note, of course, that this does not necessarily apply if GCC is being used.)

3a. The situation on this system is even more complicated than that, however. Both -lpthread (singular) and -lpthreads (plural) exist, and

3b. -lpthreads exports "pthread_create", while -lpthread exports "__pthread_create", and

3c. If you do a normal CHECK_LIBRARY_EXISTS() call, then -lpthreads appears to be the correct library. But if you do your own test program, which #includes pthread.h, pthread_create() becomes a preprocessor macro that expands to __pthread_create(). So -lpthread is the actual library needed.


Here's what I see as the takeaway:

1. If -pthread/-thread/-mt/etc. does the trick, use that in preference to any -l* library specifier.

2. The function-link test has to be done with a source file that #includes pthread.h, otherwise it's useless.

3. There's no need to special-case OSF/Tru64, because a robust enough FindThreads module can handle it.
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Issue History
Date ModifiedUsernameFieldChange
2010-05-13 19:11Daniel Richard G.New Issue
2010-08-03 12:24Kovarththanan RajaratnamCategoryCMake => Modules
2010-12-15 09:11David ColeAssigned To => Bill Hoffman
2010-12-15 09:11David ColeStatusnew => assigned
2014-10-06 16:20Rolf Eike BeerNote Added: 0036988
2016-06-10 14:28Kitware RobotNote Added: 0041696
2016-06-10 14:28Kitware RobotStatusassigned => resolved
2016-06-10 14:28Kitware RobotResolutionopen => moved
2016-06-10 14:31Kitware RobotStatusresolved => closed

Notes
(0036988)
Rolf Eike Beer   
2014-10-06 16:20   
Does using "-pthread" in both CMAKE_C_FLAGS and target_link_libraries() at the same time work? In this case this would be just another instance of "-pthread should be preferred over explicitely specifying a library". Does this problem still exist in 3.0.2 or newer at all?
(0041696)
Kitware Robot   
2016-06-10 14:28   
Resolving issue as `moved`.

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