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chuck cranor authored
The first time you run cmake, it sets the implicit include path to the value reported by the parser (and this value gets saved in CMake${lang}Compiler.cmake). But if you re-run cmake, UnixPaths.cmake blindly appends an extra /usr/include to the value saved in CMake${lang}Compiler.cmake. That should not be harmful in most cases, but we want later runs of cmake to be consistent with the initial one. Resolve using a solution suggested by Brad King: - UnixPaths now sets the default implicit include path in a new variable named _CMAKE_${lang}_IMPLICIT_INCLUDE_DIRECTORIES_INIT This value is only used the first time cmake is run (by CMakeDetermineCompilerABI.cmake when it calls the implicit include parser). - if CMakeDetermineCompilerABI.cmake successfully calls the implicit include parser, it overwrites the value in _CMAKE_${lang}_IMPLICIT_INCLUDE_DIRECTORIES_INIT with the value returned by the parser - CMakeDetermineCompilerABI.cmake always sets CMAKE_${lang}_IMPLICIT_INCLUDE_DIRECTORIES to the above value of _CMAKE_${lang}_IMPLICIT_INCLUDE_DIRECTORIES_INIT - the final value of CMAKE_${lang}_IMPLICIT_INCLUDE_DIRECTORIES gets saved to CMake${lang}Compiler.cmake when it is regenerated after the compiler tests are done. - CMakeDetermineCompilerABI.cmake is only executed the first time cmake is run. Additional runs of cmake directly load the implicit include path from the value saved in CMake${lang}Compiler.cmake (the parser and _INIT variable are not used). The above depends on UnixPaths.cmake being loaded to set the _INIT value before CMakeDetermineCompilerABI.cmake runs the implicit include parser.
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