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CMake/Modules/CMakeDetermineCompiler.cmake

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Factor common code out of CMakeDetermine(ASM|C|CXX|Fortran)Compiler The compiler candidate list selection and search code for C, C++, ASM, and Fortran languages was duplicated across four modules. To look for compilers adjacent to already-enabled languages the C and CXX modules each used _CMAKE_USER_(C|CXX)_COMPILER_PATH and the ASM module used _CMAKE_TOOLCHAIN_LOCATION. Since commit 4debb7ac (Bias Fortran compiler search with C/C++ compilers, 2009-09-09) CMake prefers Fortran compilers matching the vendor and directory of an enabled C or C++ compiler. Factor out the common functionality among the four languages into a new CMakeDetermineCompiler module. Generalize the Fortran implementation so that all languages may each use the vendor and directory of the other languages that have already been enabled. For now do not list any vendor-specific names for C, C++, or ASM so that only the directory preference is used for these languages (existing behavior).
2012-08-02 19:08:55 +04:00
#=============================================================================
# Copyright 2004-2012 Kitware, Inc.
#
# Distributed under the OSI-approved BSD License (the "License");
# see accompanying file Copyright.txt for details.
#
# This software is distributed WITHOUT ANY WARRANTY; without even the
# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the License for more information.
#=============================================================================
# (To distribute this file outside of CMake, substitute the full
# License text for the above reference.)
macro(_cmake_find_compiler lang)
# Use already-enabled languages for reference.
get_property(_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
list(REMOVE_ITEM _languages "${lang}")
if(CMAKE_${lang}_COMPILER_INIT)
# Search only for the specified compiler.
set(CMAKE_${lang}_COMPILER_LIST "${CMAKE_${lang}_COMPILER_INIT}")
else()
# Re-order the compiler list with preferred vendors first.
set(_${lang}_COMPILER_LIST "${CMAKE_${lang}_COMPILER_LIST}")
set(CMAKE_${lang}_COMPILER_LIST "")
# Prefer vendors of compilers from reference languages.
foreach(l ${_languages})
list(APPEND CMAKE_${lang}_COMPILER_LIST
${_${lang}_COMPILER_NAMES_${CMAKE_${l}_COMPILER_ID}})
endforeach()
Prefer generic system compilers by default for C, C++, and Fortran Teach CMake to prefer the system default compiler automatically when no compiler is specified. By default use "cc" for C, "CC" for C++, and "f95" for Fortran. Load a new Platform/<os>-<lang>.cmake module to allow each platform to specify for each language its system compiler name(s) and/or exclude certain names. Create Platform/(CYGWIN|Darwin|Linux|Windows)-CXX.cmake modules to specify "c++" as the system C++ compiler name for these platforms. On systems that use case-insensitive filesystems exclude C++ compiler names that are distinguished from C compiler names only by case. This will change the default compiler selection for existing build scripts that do not specify a compiler when run on machines with separate system and GNU compilers both installed in the PATH. We do not make this change in default behavior lightly. However: (1) If a given build really needs specific compilers one should specify them explicitly e.g. by setting CC, CXX, and FC in the environment. (2) The motivating case is to prefer the system Clang on newer OS X systems over the older GNU compilers typically also installed. On such systems the names "cc" and "c++" link to Clang. This is the first platform known to CMake on which "c++" is not a GNU compiler. The old behavior selected "gcc" for C and "c++" C++ and therefore chooses GNU for C and Clang for C++ by default. The new behavior selects GNU or Clang consistently for both languages on older or newer OS X systems, respectively. (3) Other than the motivating OS X case the conditions under which the behavior changes do not tend to exist in default OS installations. They typically occur only on non-GNU systems with manually-installed GNU compilers. (4) The consequences of the new behavior are not dire. At worst the project fails to compile with the system compiler when it previously worked with the non-system GNU compiler. Such failure is easy to work around (see #1). In short this change creates a more sensible default behavior everywhere and fixes poor default behavior on a widely-used platform at the cost of a modest change in behavior in less-common conditions.
2012-08-02 19:53:25 +04:00
# Prefer vendors based on the platform.
list(APPEND CMAKE_${lang}_COMPILER_LIST ${CMAKE_${lang}_COMPILER_NAMES})
Factor common code out of CMakeDetermine(ASM|C|CXX|Fortran)Compiler The compiler candidate list selection and search code for C, C++, ASM, and Fortran languages was duplicated across four modules. To look for compilers adjacent to already-enabled languages the C and CXX modules each used _CMAKE_USER_(C|CXX)_COMPILER_PATH and the ASM module used _CMAKE_TOOLCHAIN_LOCATION. Since commit 4debb7ac (Bias Fortran compiler search with C/C++ compilers, 2009-09-09) CMake prefers Fortran compilers matching the vendor and directory of an enabled C or C++ compiler. Factor out the common functionality among the four languages into a new CMakeDetermineCompiler module. Generalize the Fortran implementation so that all languages may each use the vendor and directory of the other languages that have already been enabled. For now do not list any vendor-specific names for C, C++, or ASM so that only the directory preference is used for these languages (existing behavior).
2012-08-02 19:08:55 +04:00
# Append the rest of the list and remove duplicates.
list(APPEND CMAKE_${lang}_COMPILER_LIST ${_${lang}_COMPILER_LIST})
unset(_${lang}_COMPILER_LIST)
list(REMOVE_DUPLICATES CMAKE_${lang}_COMPILER_LIST)
Prefer generic system compilers by default for C, C++, and Fortran Teach CMake to prefer the system default compiler automatically when no compiler is specified. By default use "cc" for C, "CC" for C++, and "f95" for Fortran. Load a new Platform/<os>-<lang>.cmake module to allow each platform to specify for each language its system compiler name(s) and/or exclude certain names. Create Platform/(CYGWIN|Darwin|Linux|Windows)-CXX.cmake modules to specify "c++" as the system C++ compiler name for these platforms. On systems that use case-insensitive filesystems exclude C++ compiler names that are distinguished from C compiler names only by case. This will change the default compiler selection for existing build scripts that do not specify a compiler when run on machines with separate system and GNU compilers both installed in the PATH. We do not make this change in default behavior lightly. However: (1) If a given build really needs specific compilers one should specify them explicitly e.g. by setting CC, CXX, and FC in the environment. (2) The motivating case is to prefer the system Clang on newer OS X systems over the older GNU compilers typically also installed. On such systems the names "cc" and "c++" link to Clang. This is the first platform known to CMake on which "c++" is not a GNU compiler. The old behavior selected "gcc" for C and "c++" C++ and therefore chooses GNU for C and Clang for C++ by default. The new behavior selects GNU or Clang consistently for both languages on older or newer OS X systems, respectively. (3) Other than the motivating OS X case the conditions under which the behavior changes do not tend to exist in default OS installations. They typically occur only on non-GNU systems with manually-installed GNU compilers. (4) The consequences of the new behavior are not dire. At worst the project fails to compile with the system compiler when it previously worked with the non-system GNU compiler. Such failure is easy to work around (see #1). In short this change creates a more sensible default behavior everywhere and fixes poor default behavior on a widely-used platform at the cost of a modest change in behavior in less-common conditions.
2012-08-02 19:53:25 +04:00
if(CMAKE_${lang}_COMPILER_EXCLUDE)
list(REMOVE_ITEM CMAKE_${lang}_COMPILER_LIST
${CMAKE_${lang}_COMPILER_EXCLUDE})
endif()
Factor common code out of CMakeDetermine(ASM|C|CXX|Fortran)Compiler The compiler candidate list selection and search code for C, C++, ASM, and Fortran languages was duplicated across four modules. To look for compilers adjacent to already-enabled languages the C and CXX modules each used _CMAKE_USER_(C|CXX)_COMPILER_PATH and the ASM module used _CMAKE_TOOLCHAIN_LOCATION. Since commit 4debb7ac (Bias Fortran compiler search with C/C++ compilers, 2009-09-09) CMake prefers Fortran compilers matching the vendor and directory of an enabled C or C++ compiler. Factor out the common functionality among the four languages into a new CMakeDetermineCompiler module. Generalize the Fortran implementation so that all languages may each use the vendor and directory of the other languages that have already been enabled. For now do not list any vendor-specific names for C, C++, or ASM so that only the directory preference is used for these languages (existing behavior).
2012-08-02 19:08:55 +04:00
endif()
# Look for directories containing compilers of reference languages.
set(_${lang}_COMPILER_HINTS)
foreach(l ${_languages})
if(CMAKE_${l}_COMPILER AND IS_ABSOLUTE "${CMAKE_${l}_COMPILER}")
get_filename_component(_hint "${CMAKE_${l}_COMPILER}" PATH)
if(IS_DIRECTORY "${_hint}")
list(APPEND _${lang}_COMPILER_HINTS "${_hint}")
endif()
unset(_hint)
endif()
endforeach()
# Find the compiler.
if(_${lang}_COMPILER_HINTS)
# Prefer directories containing compilers of reference languages.
list(REMOVE_DUPLICATES _${lang}_COMPILER_HINTS)
find_program(CMAKE_${lang}_COMPILER
NAMES ${CMAKE_${lang}_COMPILER_LIST}
PATHS ${_${lang}_COMPILER_HINTS}
NO_DEFAULT_PATH
DOC "${lang} compiler")
endif()
find_program(CMAKE_${lang}_COMPILER NAMES ${CMAKE_${lang}_COMPILER_LIST} DOC "${lang} compiler")
if(CMAKE_${lang}_COMPILER_INIT AND NOT CMAKE_${lang}_COMPILER)
set(CMAKE_${lang}_COMPILER "${CMAKE_${lang}_COMPILER_INIT}" CACHE FILEPATH "${lang} compiler" FORCE)
endif()
unset(_${lang}_COMPILER_HINTS)
unset(_languages)
endmacro()