Unset package_LIBRARIES cache variable in gz_pkg_check_modules_quiet

[iche033]

Signed-off-by: Ian Chen [email protected]

🦟 Bug fix

Summary

The value of package_LIBRARIES var may persist after callinggz_pkg_check_modules_quiet, and this causes an issue with subsequent calls to look for the same package.

The issue happens for me on macOS (cmake version 3.25.2) when building gz-physics from source, see comment gazebosim/gz-sim#1362 (comment). TINYXML2 is searched twice, once when cmake tries to find sdformat and again when finding DART. This results in incorrect library paths being set and linked to by DART:

ld: library not found for -lTINYXML2_LIBRARY_/opt/homebrew/Cellar/tinyxml2/9.0.0/lib/libtinyxml2.dylib-NOTFOUND
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
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[scpeters]

sounds reasonable. are there any other variables we should unset while we're at it?

[iche033]

sounds reasonable. are there any other variables we should unset while we're at it?

There're also a few variables set by pkg_check_modules. The ones that are used internally later in our code are:

• package_FOUND
• package_LIBRARIES
• package_LIBRARY_DIRS
• package_INCLUDE_DIRS

When I tried to printout these values between two pkg_check_modules calls, I see that the package_LIBRARIES is the only one whose value came out different after the second call if its previous value is not empty. I think unsetting other values maybe be fine but I left them untouched to minimize the chance of breaking things since I'm not very familiar with the implementation details of this function.

[scpeters]

sounds reasonable. are there any other variables we should unset while we're at it?

There're also a few variables set by pkg_check_modules. The ones that are used internally later in our code are:

• package_FOUND
• package_LIBRARIES
• package_LIBRARY_DIRS
• package_INCLUDE_DIRS

When I tried to printout these values between two pkg_check_modules calls, I see that the package_LIBRARIES is the only one whose value came out different after the second call if its previous value is not empty. I think unsetting other values maybe be fine but I left them untouched to minimize the chance of breaking things since I'm not very familiar with the implementation details of this function.

sounds good! I approve