[CMake] add_custom_command using CMAKE_CXX_FLAGS

[Tyler Roscoe]

On Sun, Aug 23, 2009 at 09:03:22PM -0400, John Smith wrote:
> I am using the following test case in an attempt to add a custom  
> command to build an assembly file. The assembly file should be  
> compiled with the C++ compiler driver (which in turn should invoke the  
> assembler after pre-processing), and I am building up a  
> CMAKE_CXX_FLAGS variable from separate pieces:

I think you can just hand your .S files to add_library(). Did you try
searching the ML archives or google for how to handle assembler files
with CMake?

> set(CMAKE_CXX_FLAGS -m32)

When you do this, you clobber the pre-existing value of CMAKE_CXX_FLAGS,
which has some defaults that are probably useful for your platform. Are
you sure this is what you want?

> set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pthread")
> 
> message (STATUS "CMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}")
> 
> file (GLOB ASM_SRCS bar.S)

As a general rule, you probably don't want to use file (GLOB ...). Here
you can just say set(ASM_SRCS bar.S).

> foreach (src ${ASM_SRCS})
>    get_filename_component (FILE_BASE ${src} NAME_WE)
>    set (SRC ${src})
>    set (OBJ ${CMAKE_CURRENT_BINARY_DIR}/${FILE_BASE}.o)
>    add_custom_command (OUTPUT ${OBJ}
>        MAIN_DEPENDENCY ${SRC}
>        COMMAND ${CMAKE_CXX_COMPILER}
>        ARGS ${CMAKE_CXX_FLAGS} -o ${OBJ} -c ${SRC}
>        MAIN_DEPENDENCY ${src})
>        set (ASM_OBJS ${ASM_OBJS} ${OBJ})
> endforeach(src)
> 
> add_library(test SHARED foo.cpp bar.S)

Yeah I think you're overthinking this. Look for some CMake examples that
use assembler and go from there.

tyler