Bug#943312: cmake: FindMPI.cmake does not work during cross compilation
Package: cmake
Version: 3.13.4-1
Tags: patch upstream
User: debian-cross@lists.debian.org
Usertags: ftcbfs
Control: affects -1 + src:flann src:hyphy src:liggghts src:sopt
FindMPI.cmake uses compiler wrappers such as mpicc to discover the
relevant compiler and linker flags. During cross compilation, these
compiler wrappers do not work and they will not be supported on Debian.
Beyond breaking cross compilation, you cannot easily combine multiple
compiler wrappers (e.g. ccache/distcc/mpicc). It is best to avoid
compiler wrappers entirely and for MPI, this is well supported as all
major implementations ship pkg-config files since ages. I am asking to
stop using mpicc and switch over to pkg-config.
Unfortunately, FindMPI.cmake exposes MPI_*_COMPILER and a number of
downstreams use these wrappers that cannot be used during cross
compilation. Every downstream that wants to be cross buildable must stop
using them and I've filed a relevant patch for liggghts. Avoiding
MPI_*_COMPILER is easy enough in the majority of cases, because
FindMPI.cmake also provides the relevant flags in via other variables.
Still, we must maintain backwards compatibility and thus continue
supplying MPI_*_COMPILER when it is available (i.e. during native
compilation).
The attached patch thus tries the wrappers first before falling back to
pkg-config. I've tested it with flann, hyphy, liggghts and sopt. Of
these, flann and sopt are fixed by this patch. hyphy and liggghts need
further patches, which are submitted separately. Please consider
applying the attached patch.
Helmut
--- cmake-3.13.4.orig/Modules/FindMPI.cmake
+++ cmake-3.13.4/Modules/FindMPI.cmake
@@ -247,6 +247,7 @@
cmake_policy(SET CMP0057 NEW) # if IN_LIST
include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/FindPkgConfig.cmake)
# Generic compiler names
set(_MPI_C_GENERIC_COMPILER_NAMES mpicc mpcc mpicc_r mpcc_r)
@@ -1459,7 +1460,40 @@
if(NOT MPI_PINNED_COMPILER AND NOT MPI_${LANG}_WRAPPER_FOUND)
# If MPI_PINNED_COMPILER wasn't given, and the MPI compiler we potentially found didn't work, we withdraw it.
set(MPI_${LANG}_COMPILER "MPI_${LANG}_COMPILER-NOTFOUND" CACHE FILEPATH "MPI compiler for ${LANG}" FORCE)
- if(NOT MPI_SKIP_GUESSING)
+
+ if(LANG STREQUAL "C")
+ set(_MPI_PKG "mpi-c")
+ elseif(LANG STREQUAL "CXX")
+ set(_MPI_PKG "mpi-cxx")
+ elseif(LANG STREQUAL "Fortran")
+ set(_MPI_PKG "mpi-fort")
+ else()
+ set(_MPI_PKG "")
+ endif()
+ if(_MPI_PKG)
+ pkg_check_modules("MPI_${LANG}_PKG" "${_MPI_PKG}")
+ if("${MPI_${LANG}_PKG_FOUND}")
+ set(MPI_${LANG}_COMPILE_OPTIONS ${MPI_${LANG}_PKG_CFLAGS} CACHE STRING "MPI ${LANG} compilation options" FORCE)
+ set(MPI_${LANG}_INCLUDE_PATH ${MPI_${LANG}_PKG_INCLUDE_DIRS} CACHE STRING "MPI ${LANG} include directories" FORCE)
+ set(MPI_${LANG}_LINK_FLAGS ${MPI_${LANG}_PKG_LDFLAGS} CACHE STRING "MPI ${LANG} linker flags" FORCE)
+ set(MPI_${LANG}_LIB_NAMES ${MPI_${LANG}_PKG_LIBRARIES} CACHE STRING "MPI ${LANG} libraries to link against" FORCE)
+ foreach(_MPI_LIB IN LISTS MPI_${LANG}_LIB_NAMES)
+ if(_MPI_LIB)
+ get_filename_component(_MPI_PLAIN_LIB_NAME "${_MPI_LIB}" NAME_WE)
+ get_filename_component(_MPI_LIB_NAME "${_MPI_LIB}" NAME)
+ get_filename_component(_MPI_LIB_DIR "${_MPI_LIB}" DIRECTORY)
+ find_library(MPI_${_MPI_PLAIN_LIB_NAME}_LIBRARY
+ NAMES "${_MPI_LIB_NAME}" "lib${_MPI_LIB_NAME}"
+ HINTS ${_MPI_LIB_DIR}
+ DOC "Location of the ${_MPI_PLAIN_LIB_NAME} library for MPI"
+ )
+ mark_as_advanced(MPI_${_MPI_PLAIN_LIB_NAME}_LIBRARY)
+ endif()
+ endforeach()
+ endif()
+ endif()
+
+ if(NOT MPI_SKIP_GUESSING AND NOT "${MPI_${LANG}_PKG_FOUND}")
# For C++, we may use the settings for C. Should a given compiler wrapper for C++ not exist, but one for C does, we copy over the
# settings for C. An MPI distribution that is in this situation would be IBM Platform MPI.
if("${LANG}" STREQUAL "CXX" AND MPI_C_WRAPPER_FOUND)
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