[cmake-developers] [CMake 0015804]: FindPkgConfig pkg_check_modules command should return full path to shared libraries in _LIBRARIES variable

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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https://cmake.org/Bug/view.php?id=15804 
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Reported By:                Sam Thursfield
Assigned To:                
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Project:                    CMake
Issue ID:                   15804
Category:                   Modules
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
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Date Submitted:             2015-10-20 05:32 EDT
Last Modified:              2015-10-20 05:32 EDT
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Summary:                    FindPkgConfig pkg_check_modules command should
return full path to shared libraries in _LIBRARIES variable
Description: 
CMake seems to encourage using absolute paths to shared libraries.

>From link_directories() documentation:

       Note that this command is rarely necessary.  Library locations returned
       by find_package() and find_library() are absolute  paths.   Pass  these
       absolute  library  file  paths  directly to the target_link_libraries()
       command.  CMake will ensure the linker finds them.

However, the FindPkgConfig module doesn't follow this, and instead returns just
the names of libraries, plus a linker path. Since CMake makes it awkward to
propagate the linker path, so the end result is that if you have a package
installed in a non-standard library path, things break.

Steps to Reproduce: 
An example pkg-config file:

  cmake_minimum_required(VERSION 3.3.2)

  find_package(PkgConfig REQUIRED)

  pkg_check_modules(ZLIB zlib REQUIRED)

  message("ZLIB_LIBRARIES: ${ZLIB_LIBRARIES}")
  message("ZLIB_LIBRARY_DIRS: ${ZLIB_LIBRARY_DIRS}")

Output:

  ZLIB_LIBRARIES: z
  ZLIB_LIBRARY_DIRS: /usr/lib64

Expected output:

  ZLIB_LIBRARIES: /usr/lib64/libz.so


Additional Information: 
I'm aware that in the case of Zlib there is a FindZLib module, and /usr/lib64 is
in my library search path in any case. This is just an example. The painful case
is where I had to build a library from source myself and then install it into a
non-standard prefix.
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Issue History 
Date Modified    Username       Field                    Change               
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2015-10-20 05:32 Sam Thursfield New Issue                                    
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