(0031561)
Brad King (manager)
2012-11-15 10:56

For the IDE generator CMake never generates any project file settings to change the .obj extension, for an OBJECT library or otherwise. This would be a new general-purpose feature, no? Since the VS IDE does not present any interface treating object files as first-class entities (it calls them "intermediate" files), what difference does the extension make?

Note that OBJECT libraries have no packaged library file. The ".lib" built by the IDE is hidden away and not used and only exists because we can't stop the IDE from running its librarian. When the OBJECT library is referenced in another target then CMake directly adds the .obj files to the link line for that target. They will be included among the .obj files compiled from sources in that other (real) target when linking. Those will also always have ".obj" as their extension.

The CMAKE_C_OUTPUT_EXTENSION variables are only used for non-IDE generators IIRC.

(0031562)
Mike Smith (reporter)
2012-11-15 11:14

The problem I am facing has come about because I am building using Visual Studio but with a non-Win32 cl.exe which creates .o object files, not .obj files. In the project files created by cmake it is .obj files listed but these can never be found during the build as the compiler produces .o files. The only work-around I have found so far is to manually hack the .vcxproj files after cmake has created them which isn't ideal.

> This would be a new general-purpose feature, no?
Yes, I guess so.

(0031563)
Brad King (manager)
2012-11-15 11:27

I see. Each generator has a "ComputeTargetObjects" method to predict the location of the object files. For VS it is here:

http://cmake.org/gitweb?p=cmake.git;a=blob;f=Source/cmGlobalVisualStudioGenerator.cxx;hb=v2.8.10.1#l113 [^]

Currently it hard-codes ".obj". Try teaching it to lookup the value through gt->Makefile->GetDefinition(...).

(0031608)
Mike Smith (reporter)
2012-11-19 10:03

I tried your suggestion with CMAKE_C_OUTPUT_EXTENSION but it still always comes out as ".obj" (or NULL). Where would this value get set? I can take a look to see what is happening there.

(0031609)
Brad King (manager)
2012-11-19 10:09

The value of CMAKE_C_OUTPUT_EXTENSION is initialized here:

http://cmake.org/gitweb?p=cmake.git;a=blob;f=Modules/CMakeCInformation.cmake;hb=v2.8.10.1#l21 [^]

but may be overridden by platform/compiler-specific modules loaded later in that file.

(0039297)
Bastien Schatt (reporter)
2015-08-18 10:26

I attached a patch based on your suggestion (i.e. using the value of CMAKE_C_OUTPUT_EXTENSION).

(0039298)
Brad King (manager)
2015-08-18 10:42

Thanks. The proper extension can be obtained from cmGlobalGenerator::GetLanguageOutputExtension, just like cmLocalGenerator::GetObjectFileNameWithoutTarget does. Please revise to use that instead. Otherwise this will only work when C is enabled.

(0039299)
Bastien Schatt (reporter)
2015-08-18 11:20

Thank you for the review. I didn't know about GetLanguageOutputExtension.

I attached a new patch (0001-Fixed-issue-0013685-using-GetLanguageOutputExtension.patch).

(0039304)
Brad King (manager)
2015-08-20 09:41

Re 0013685:0039299: Thanks, applied:

cmLocalVisualStudioGenerator: Use computed .obj extension
http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=3e94f94b [^]

(0040117)
Robert Maynard (manager)
2016-01-04 11:52

Closing resolved issues that have not been updated in more than 4 months.

Notes
(0031561) Brad King (manager) 2012-11-15 10:56	For the IDE generator CMake never generates any project file settings to change the .obj extension, for an OBJECT library or otherwise. This would be a new general-purpose feature, no? Since the VS IDE does not present any interface treating object files as first-class entities (it calls them "intermediate" files), what difference does the extension make? Note that OBJECT libraries have no packaged library file. The ".lib" built by the IDE is hidden away and not used and only exists because we can't stop the IDE from running its librarian. When the OBJECT library is referenced in another target then CMake directly adds the .obj files to the link line for that target. They will be included among the .obj files compiled from sources in that other (real) target when linking. Those will also always have ".obj" as their extension. The CMAKE_C_OUTPUT_EXTENSION variables are only used for non-IDE generators IIRC.

(0031562) Mike Smith (reporter) 2012-11-15 11:14	The problem I am facing has come about because I am building using Visual Studio but with a non-Win32 cl.exe which creates .o object files, not .obj files. In the project files created by cmake it is .obj files listed but these can never be found during the build as the compiler produces .o files. The only work-around I have found so far is to manually hack the .vcxproj files after cmake has created them which isn't ideal. > This would be a new general-purpose feature, no? Yes, I guess so.

(0031563) Brad King (manager) 2012-11-15 11:27	I see. Each generator has a "ComputeTargetObjects" method to predict the location of the object files. For VS it is here: http://cmake.org/gitweb?p=cmake.git;a=blob;f=Source/cmGlobalVisualStudioGenerator.cxx;hb=v2.8.10.1#l113 [^] Currently it hard-codes ".obj". Try teaching it to lookup the value through gt->Makefile->GetDefinition(...).

(0031608) Mike Smith (reporter) 2012-11-19 10:03	I tried your suggestion with CMAKE_C_OUTPUT_EXTENSION but it still always comes out as ".obj" (or NULL). Where would this value get set? I can take a look to see what is happening there.

(0031609) Brad King (manager) 2012-11-19 10:09	The value of CMAKE_C_OUTPUT_EXTENSION is initialized here: http://cmake.org/gitweb?p=cmake.git;a=blob;f=Modules/CMakeCInformation.cmake;hb=v2.8.10.1#l21 [^] but may be overridden by platform/compiler-specific modules loaded later in that file.

(0039297) Bastien Schatt (reporter) 2015-08-18 10:26	I attached a patch based on your suggestion (i.e. using the value of CMAKE_C_OUTPUT_EXTENSION).

(0039298) Brad King (manager) 2015-08-18 10:42	Thanks. The proper extension can be obtained from cmGlobalGenerator::GetLanguageOutputExtension, just like cmLocalGenerator::GetObjectFileNameWithoutTarget does. Please revise to use that instead. Otherwise this will only work when C is enabled.

(0039299) Bastien Schatt (reporter) 2015-08-18 11:20	Thank you for the review. I didn't know about GetLanguageOutputExtension. I attached a new patch (0001-Fixed-issue-0013685-using-GetLanguageOutputExtension.patch).

(0039304) Brad King (manager) 2015-08-20 09:41	Re 0013685:0039299: Thanks, applied: cmLocalVisualStudioGenerator: Use computed .obj extension http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=3e94f94b [^]

(0040117) Robert Maynard (manager) 2016-01-04 11:52	Closing resolved issues that have not been updated in more than 4 months.

Issue History
Date Modified	Username	Field	Change
2012-11-15 10:36	Mike Smith	New Issue
2012-11-15 10:36	Mike Smith	File Added: cmake-test.zip
2012-11-15 10:56	Brad King	Note Added: 0031561
2012-11-15 11:14	Mike Smith	Note Added: 0031562
2012-11-15 11:27	Brad King	Note Added: 0031563
2012-11-15 11:27	Brad King	Severity	minor => feature
2012-11-15 11:27	Brad King	Status	new => backlog
2012-11-19 10:03	Mike Smith	Note Added: 0031608
2012-11-19 10:09	Brad King	Note Added: 0031609
2015-08-18 10:20	Bastien Schatt	File Added: 0001-Fixed-issue-0013685.patch
2015-08-18 10:26	Bastien Schatt	Note Added: 0039297
2015-08-18 10:42	Brad King	Note Added: 0039298
2015-08-18 11:05	Bastien Schatt	File Added: 0001-Fixed-coding-style.patch
2015-08-18 11:18	Bastien Schatt	File Added: 0001-Fixed-issue-0013685-using-GetLanguageOutputExtension.patch
2015-08-18 11:20	Bastien Schatt	Note Added: 0039299
2015-08-20 09:41	Brad King	Note Added: 0039304
2015-08-20 09:41	Brad King	Status	backlog => resolved
2015-08-20 09:41	Brad King	Resolution	open => fixed
2015-08-20 09:41	Brad King	Fixed in Version	=> CMake 3.4
2015-08-20 09:41	Brad King	Target Version	=> CMake 3.4
2016-01-04 11:52	Robert Maynard	Note Added: 0040117
2016-01-04 11:52	Robert Maynard	Status	resolved => closed

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