I'm developing a library on and for a multitude of platforms and would
like to provide both 32 and 64-bit versions for all platforms this is
relevant for.
I'm currently on Ubuntu 64bit with CMake 3.5.2 and use the "-m32"
compiler switch to do the 32-bit compile.
I'm trying to understand why GNUInstallDirs are not setting
CMAKE_INSTALL_LIBDIR to what I think it should. While doing that I
discovered that CMAKE_SIZEOF_VOID_P is not set as I thought it would
either.
According to the documentation CMAKE_SIZEOF_VOID_P it is determined by
running the compiler. However it seems that it is not using pertinent
flags from the configuration, in particular CMAKE_C_FLAGS and
CMAKE_CXX_FLAGS.
Having a CMakeLists.txt containing:
cmake_minimum_required(VERSION 2.8.5)
project(X C)
try_run(run_result_var compile_result_var /tmp /tmp/size.c)
message(STATUS "Sizeof=" ${run_result_var})
message(STATUS "CMAKE_SIZEOF_VOID_P=" ${CMAKE_SIZEOF_VOID_P})
and size.c with:
int main(int argc, char **argv) {
return sizeof(void *);
}
With no flags I get:
-- Sizeof=8
-- CMAKE_SIZEOF_VOID_P=8
And with CMAKE_C_FLAGS set to "-m32" I get:
-- Sizeof=4
-- CMAKE_SIZEOF_VOID_P=8
If this is by design, then I think the documentation is unclear, if not
plain wrong:
This is set to the size of a pointer on the target machine, and is
determined by a try compile.
If a 64-bit size is found, then the library search path is modified
to look for 64-bit libraries first.
Or am I missing something?
/Thomas
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