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|
#
# - This module provides the function
# target_link_libraries_with_dynamic_lookup which can be used to
# "weakly" link a loadable module.
#
# Link a library to a target such that the symbols are resolved at
# run-time not link-time. This should be used when compiling a
# loadable module when the symbols should be resolve from the run-time
# environment where the module is loaded, and not a specific system
# library.
#
# Specifically, for OSX it uses undefined dynamic_lookup. This is
# similar to using "-shared" on Linux where undefined symbols are
# ignored.
#
# Additionally, the linker is checked to see if it supports undefined
# symbols when linking a shared library. If it does then the library
# is not linked when specified with this function.
#
# http://blog.tim-smith.us/2015/09/python-extension-modules-os-x/
#
#
# The following functions are defined:
#
# _get_target_type(<ResultVar> <Target>)
#
# **INTERNAL** Shorthand for querying an abbreviated version of the target type
# of the given ``<Target>``. ``<ResultVar>`` is set to "STATIC" for a
# STATIC_LIBRARY, "SHARED" for a SHARED_LIBRARY, "MODULE" for a MODULE_LIBRARY,
# and "EXE" for an EXECUTABLE.
#
# Defined variables:
#
# ``<ResultVar>``
# The abbreviated version of the ``<Target>``'s type.
#
#
# _test_weak_link_project(<TargetType>
# <LibType>
# <ResultVar>
# <LinkFlagsVar>)
#
# **INTERNAL** Attempt to compile and run a test project where a target of type
# ``<TargetType>`` is weakly-linked against a dependency of type ``<LibType>``.
# ``<TargetType>`` can be one of "STATIC", "SHARED", "MODULE", or "EXE".
# ``<LibType>`` can be one of "STATIC", "SHARED", or "MODULE".
#
# Defined variables:
#
# ``<ResultVar>``
# Whether the current C toolchain can produce a working target binary of type
# ``<TargetType>`` that is weakly-linked against a dependency target of type
# ``<LibType>``.
#
# ``<LinkFlagsVar>``
# List of flags to add to the linker command to produce a working target
# binary of type ``<TargetType>`` that is weakly-linked against a dependency
# target of type ``<LibType>``.
#
#
# check_dynamic_lookup(<TargetType>
# <LibType>
# <ResultVar>
# <LinkFlagsVar>)
#
# Check if the linker requires a command line flag to allow leaving symbols
# unresolved when producing a target of type ``<TargetType>`` that is
# weakly-linked against a dependency of type ``<LibType>``. ``<TargetType>``
# can be one of "STATIC", "SHARED", "MODULE", or "EXE". ``<LibType>`` can be
# one of "STATIC", "SHARED", or "MODULE". The result is cached between
# invocations and recomputed only when the value of CMake's linker flag list
# changes; ``CMAKE_STATIC_LINKER_FLAGS`` if ``<TargetType>`` is "STATIC", and
# ``CMAKE_SHARED_LINKER_FLAGS`` otherwise.
#
#
# Defined variables:
#
# ``<ResultVar>``
# Whether the current C toolchain supports weak-linking for target binaries of
# type ``<TargetType>`` that are weakly-linked against a dependency target of
# type ``<LibType>``.
#
# ``<LinkFlagsVar>``
# List of flags to add to the linker command to produce a working target
# binary of type ``<TargetType>`` that is weakly-linked against a dependency
# target of type ``<LibType>``.
#
# ``HAS_DYNAMIC_LOOKUP_<TargetType>_<LibType>``
# Cached, global alias for ``<ResultVar>``
#
# ``DYNAMIC_LOOKUP_FLAGS_<TargetType>_<LibType>``
# Cached, global alias for ``<LinkFlagsVar>``
#
#
# target_link_libraries_with_dynamic_lookup(<Target> [<Libraries>])
#
# Like proper linking, except that the given ``<Libraries>`` are not necessarily
# linked. Instead, the ``<Target>`` is produced in a manner that allows for
# symbols unresolved within it to be resolved at runtime, presumably by the
# given ``<Libraries>``. If such a target can be produced, the provided
# ``<Libraries>`` are not actually linked. On platforms that do not support
# weak-linking, this function works just like ``target_link_libraries``.
function(_get_target_type result_var target)
set(target_type "SHARED_LIBRARY")
if(TARGET ${target})
get_property(target_type TARGET ${target} PROPERTY TYPE)
endif()
set(result "STATIC")
if(target_type STREQUAL "STATIC_LIBRARY")
set(result "STATIC")
endif()
if(target_type STREQUAL "SHARED_LIBRARY")
set(result "SHARED")
endif()
if(target_type STREQUAL "MODULE_LIBRARY")
set(result "MODULE")
endif()
if(target_type STREQUAL "EXECUTABLE")
set(result "EXE")
endif()
set(${result_var} ${result} PARENT_SCOPE)
endfunction()
function(_test_weak_link_project
target_type
lib_type
can_weak_link_var
project_name)
set(gnu_ld_ignore "-Wl,--unresolved-symbols=ignore-all")
set(osx_dynamic_lookup "-undefined dynamic_lookup")
set(no_flag "")
foreach(link_flag_spec gnu_ld_ignore osx_dynamic_lookup no_flag)
set(link_flag "${${link_flag_spec}}")
set(test_project_dir "${PROJECT_BINARY_DIR}/CMakeTmp")
set(test_project_dir "${test_project_dir}/${project_name}")
set(test_project_dir "${test_project_dir}/${link_flag_spec}")
set(test_project_dir "${test_project_dir}/${target_type}")
set(test_project_dir "${test_project_dir}/${lib_type}")
set(test_project_src_dir "${test_project_dir}/src")
set(test_project_bin_dir "${test_project_dir}/build")
file(MAKE_DIRECTORY ${test_project_src_dir})
file(MAKE_DIRECTORY ${test_project_bin_dir})
set(mod_type "STATIC")
set(link_mod_lib TRUE)
set(link_exe_lib TRUE)
set(link_exe_mod FALSE)
if("${target_type}" STREQUAL "EXE")
set(link_exe_lib FALSE)
set(link_exe_mod TRUE)
else()
set(mod_type "${target_type}")
endif()
if("${mod_type}" STREQUAL "MODULE")
set(link_mod_lib FALSE)
endif()
file(WRITE "${test_project_src_dir}/CMakeLists.txt" "
cmake_minimum_required(VERSION ${CMAKE_VERSION})
project(${project_name} C)
include_directories(${test_project_src_dir})
add_library(number ${lib_type} number.c)
add_library(counter ${mod_type} counter.c)
")
if("${mod_type}" STREQUAL "MODULE")
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
set_target_properties(counter PROPERTIES PREFIX \"\")
")
endif()
if(link_mod_lib)
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
target_link_libraries(counter number)
")
elseif(NOT link_flag STREQUAL "")
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
set_target_properties(counter PROPERTIES LINK_FLAGS \"${link_flag}\")
")
endif()
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
add_executable(main main.c)
")
if(link_exe_lib)
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
target_link_libraries(main number)
")
elseif(NOT link_flag STREQUAL "")
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
target_link_libraries(main \"${link_flag}\")
")
endif()
if(link_exe_mod)
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
target_link_libraries(main counter)
")
else()
file(APPEND "${test_project_src_dir}/CMakeLists.txt" "
target_link_libraries(main \"${CMAKE_DL_LIBS}\")
")
endif()
file(WRITE "${test_project_src_dir}/number.c" "
#include <number.h>
static int _number;
void set_number(int number) { _number = number; }
int get_number() { return _number; }
")
file(WRITE "${test_project_src_dir}/number.h" "
#ifndef _NUMBER_H
#define _NUMBER_H
extern void set_number(int);
extern int get_number(void);
#endif
")
file(WRITE "${test_project_src_dir}/counter.c" "
#include <number.h>
int count() {
int result = get_number();
set_number(result + 1);
return result;
}
")
file(WRITE "${test_project_src_dir}/counter.h" "
#ifndef _COUNTER_H
#define _COUNTER_H
extern int count(void);
#endif
")
file(WRITE "${test_project_src_dir}/main.c" "
#include <stdlib.h>
#include <stdio.h>
#include <number.h>
")
if(NOT link_exe_mod)
file(APPEND "${test_project_src_dir}/main.c" "
#include <dlfcn.h>
")
endif()
file(APPEND "${test_project_src_dir}/main.c" "
int my_count() {
int result = get_number();
set_number(result + 1);
return result;
}
int main(int argc, char **argv) {
int result;
")
if(NOT link_exe_mod)
file(APPEND "${test_project_src_dir}/main.c" "
void *counter_module;
int (*count)(void);
counter_module = dlopen(\"./counter.so\", RTLD_LAZY | RTLD_GLOBAL);
if(!counter_module) goto error;
count = dlsym(counter_module, \"count\");
if(!count) goto error;
")
endif()
file(APPEND "${test_project_src_dir}/main.c" "
result = count() != 0 ? EXIT_FAILURE :
my_count() != 1 ? EXIT_FAILURE :
my_count() != 2 ? EXIT_FAILURE :
count() != 3 ? EXIT_FAILURE :
count() != 4 ? EXIT_FAILURE :
count() != 5 ? EXIT_FAILURE :
my_count() != 6 ? EXIT_FAILURE : EXIT_SUCCESS;
")
if(NOT link_exe_mod)
file(APPEND "${test_project_src_dir}/main.c" "
goto done;
error:
fprintf(stderr, \"Error occured:\\n %s\\n\", dlerror());
result = 1;
done:
if(counter_module) dlclose(counter_module);
")
endif()
file(APPEND "${test_project_src_dir}/main.c" "
return result;
}
")
set(_rpath_arg)
if(APPLE AND ${CMAKE_VERSION} VERSION_GREATER 2.8.11)
set(_rpath_arg "-DCMAKE_MACOSX_RPATH='${CMAKE_MACOSX_RPATH}'")
endif()
try_compile(project_compiles
"${test_project_bin_dir}"
"${test_project_src_dir}"
"${project_name}"
CMAKE_FLAGS
"-DCMAKE_SHARED_LINKER_FLAGS='${CMAKE_SHARED_LINKER_FLAGS}'"
${_rpath_arg}
OUTPUT_VARIABLE compile_output)
set(project_works 1)
set(run_output)
if(project_compiles)
execute_process(COMMAND ${CMAKE_CROSSCOMPILING_EMULATOR}
"${test_project_bin_dir}/main"
WORKING_DIRECTORY "${test_project_bin_dir}"
RESULT_VARIABLE project_works
OUTPUT_VARIABLE run_output
ERROR_VARIABLE run_output)
endif()
set(test_description
"Weak Link ${target_type} -> ${lib_type} (${link_flag_spec})")
if(project_works EQUAL 0)
set(project_works TRUE)
message(STATUS "Performing Test ${test_description} - Success")
else()
set(project_works FALSE)
message(STATUS "Performing Test ${test_description} - Failed")
file(APPEND ${CMAKE_BINARY_DIR}/${CMAKE_FILES_DIRECTORY}/CMakeError.log
"Performing Test ${test_description} failed with the "
"following output:\n"
"BUILD\n-----\n${compile_output}\nRUN\n---\n${run_output}\n")
endif()
set(${can_weak_link_var} ${project_works} PARENT_SCOPE)
if(project_works)
set(${project_name} ${link_flag} PARENT_SCOPE)
break()
endif()
endforeach()
endfunction()
function(check_dynamic_lookup
target_type
lib_type
has_dynamic_lookup_var
link_flags_var)
# hash the CMAKE_FLAGS passed and check cache to know if we need to rerun
if("${target_type}" STREQUAL "STATIC")
string(MD5 cmake_flags_hash "${CMAKE_STATIC_LINKER_FLAGS}")
else()
string(MD5 cmake_flags_hash "${CMAKE_SHARED_LINKER_FLAGS}")
endif()
set(cache_var "HAS_DYNAMIC_LOOKUP_${target_type}_${lib_type}")
set(cache_hash_var "HAS_DYNAMIC_LOOKUP_${target_type}_${lib_type}_hash")
set(result_var "DYNAMIC_LOOKUP_FLAGS_${target_type}_${lib_type}")
if( NOT DEFINED ${cache_hash_var}
OR NOT "${${cache_hash_var}}" STREQUAL "${cmake_flags_hash}")
unset(${cache_var} CACHE)
endif()
if(NOT DEFINED ${cache_var})
set(skip_test FALSE)
if(NOT CMAKE_CROSSCOMPILING)
set(skip_test TRUE)
elseif(CMAKE_CROSSCOMPILING AND CMAKE_CROSSCOMPILING_EMULATOR)
set(skip_test TRUE)
endif()
if(skip_test)
set(has_dynamic_lookup FALSE)
set(link_flags)
else()
_test_weak_link_project(${target_type}
${lib_type}
has_dynamic_lookup
link_flags)
endif()
set(caveat " (when linking ${target_type} against ${lib_type})")
set(${cache_var} "${has_dynamic_lookup}"
CACHE BOOL
"linker supports dynamic lookup for undefined symbols${caveat}")
set(${result_var} "${link_flags}"
CACHE BOOL
"linker flags for dynamic lookup${caveat}")
set(${cache_hash_var} "${cmake_flags_hash}"
CACHE INTERNAL "hashed flags for ${cache_var} check")
endif()
set(${has_dynamic_lookup_var} "${${cache_var}}" PARENT_SCOPE)
set(${link_flags_var} "${${result_var}}" PARENT_SCOPE)
endfunction()
function(target_link_libraries_with_dynamic_lookup target)
_get_target_type(target_type ${target})
set(link_props)
set(link_items)
set(link_libs)
foreach(lib ${ARGN})
_get_target_type(lib_type ${lib})
check_dynamic_lookup(${target_type}
${lib_type}
has_dynamic_lookup
dynamic_lookup_flags)
if(has_dynamic_lookup)
if(dynamic_lookup_flags)
if("${target_type}" STREQUAL "EXE")
list(APPEND link_items "${dynamic_lookup_flags}")
else()
list(APPEND link_props "${dynamic_lookup_flags}")
endif()
endif()
else()
list(APPEND link_libs "${lib}")
endif()
endforeach()
if(link_props)
list(REMOVE_DUPLICATES link_props)
endif()
if(link_items)
list(REMOVE_DUPLICATES link_items)
endif()
if(link_libs)
list(REMOVE_DUPLICATES link_libs)
endif()
if(link_props)
set_target_properties(${target}
PROPERTIES LINK_FLAGS "${link_props}")
endif()
set(links "${link_items}" "${link_libs}")
if(links)
target_link_libraries(${target} "${links}")
endif()
endfunction()
|
