I want to pass result of the getconf PAGESIZE command output as preprocessor define to my program in form of -DPAGESIZE=`getconf PAGESIZE` for [[gnu::assume_aligned(PAGESIZE)]] in custom allocator declaration.
I tried the following:
add_definitions(-DPAGESIZE=`getconf PAGESIZE`)
But it expanded exactly as -DPAGESIZE="\`getconf" ... PAGESIZE`, where ... is contents of other CMAKE_CXX_FLAGS*. I.e. there is an issue with escaping of backticks in CMakeLists.txt files.
How to properly pass such an arguments to compiler/linker in CMakeLists.txt files? Maybe is there another way to achieve desired?
Also I tried add_definitions(-DPAGESIZE="$$(getconf PAGESIZE)") ($$ expanded as $ by cmake), but -DPAGESIZE and the rest part are splitted by cmake. add_definitions("-DPAGESIZE=$$(getconf PAGESIZE)") makes cmake to escape every dollar sign though.
According to documentation for add_definitions command, preprocessor definitions, passed to this command, are appended to COMPILE_DEFINITIONS property:
Flags beginning in -D or /D that look like preprocessor definitions are automatically added to the COMPILE_DEFINITIONS directory property for the current directory.
And content of COMPILE_DEFINITIONS property, according to its documentation is always escaped by CMake, so you cannot preserve special meaning of backticks in the build command:
CMake will automatically escape the value correctly for the native build system
Your may modify CMAKE_CXX_FLAGS manually, as you show in your comment.
The better way is to use execute_process command for run needed command at configuration stage, and use its output for add_definitions command. (Or use this output for create additional header file with configure_file).