emmaken.py needs to distinguish c from c++

[paleozogt]

With CMake its possible to compile .c files as C++. This is an unfortunate yet common practice in large, legacy codebases. emmaken.py uses the extension to figure out which compiler it needs to use, but this fails with .c files that are really c++.

For example, using helloworld.c:

#include <stdio.h>

// C++ headers
#include <cmath>
#include <limits>

int helloworld(void) {
   printf("helloworld \n");
   return 0;
}

and CMakeLists.txt:

cmake_minimum_required(VERSION 2.8.3)

# these must be set *before* project()
if (EMSCRIPTEN)
    set(EMSCRIPTEN_TOOLS ${EMSCRIPTEN_HOME}/tools)
    SET(CMAKE_C_COMPILER          "${EMSCRIPTEN_TOOLS}/emmaken.py")
    SET(CMAKE_CXX_COMPILER        "${EMSCRIPTEN_TOOLS}/emmaken.py")
    SET(CMAKE_LINKER              "${EMSCRIPTEN_TOOLS}/emmaken.py")
    SET(CMAKE_CXX_LINKER          "${EMSCRIPTEN_TOOLS}/emmaken.py")
    SET(CMAKE_C_LINK_EXECUTABLE   "${EMSCRIPTEN_TOOLS}/emmaken.py")
    SET(CMAKE_CXX_LINK_EXECUTABLE "${EMSCRIPTEN_TOOLS}/emmaken.py")
endif(EMSCRIPTEN)

project(helloworld)

# these must be set *after* project()
if (EMSCRIPTEN)
    SET(CMAKE_AR                  "${EMSCRIPTEN_TOOLS}/emmaken.py")
    SET(CMAKE_RANLIB              "${EMSCRIPTEN_TOOLS}/emmaken.py")
endif(EMSCRIPTEN)

# list of sources
set(SRCS helloworld.c)

# compile all files as C++, no matter their extension
set_source_files_properties( ${SRCS} PROPERTIES LANGUAGE CXX )

# make a lib
add_library(helloworld ${SRCS})

has this output:

$ cmake .. -DEMSCRIPTEN=1 -DEMSCRIPTEN_HOME=/home/vail/Development/emscripten; make VERBOSE=1
-- The C compiler identification is unknown
-- The CXX compiler identification is unknown
-- Check for working C compiler: /home/vail/Development/emscripten/tools/emmaken.py
-- Check for working C compiler: /home/vail/Development/emscripten/tools/emmaken.py -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /home/vail/Development/emscripten/tools/emmaken.py
-- Check for working CXX compiler: /home/vail/Development/emscripten/tools/emmaken.py -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/vail/Development/helloworld/.build-js
/usr/bin/cmake -H/home/vail/Development/helloworld -B/home/vail/Development/helloworld/.build-js --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/vail/Development/helloworld/.build-js/CMakeFiles /home/vail/Development/helloworld/.build-js/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/vail/Development/helloworld/.build-js'
make -f CMakeFiles/helloworld.dir/build.make CMakeFiles/helloworld.dir/depend
make[2]: Entering directory `/home/vail/Development/helloworld/.build-js'
cd /home/vail/Development/helloworld/.build-js && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/vail/Development/helloworld /home/vail/Development/helloworld /home/vail/Development/helloworld/.build-js /home/vail/Development/helloworld/.build-js /home/vail/Development/helloworld/.build-js/CMakeFiles/helloworld.dir/DependInfo.cmake --color=
Dependee "/home/vail/Development/helloworld/.build-js/CMakeFiles/helloworld.dir/DependInfo.cmake" is newer than depender "/home/vail/Development/helloworld/.build-js/CMakeFiles/helloworld.dir/depend.internal".
Dependee "/home/vail/Development/helloworld/.build-js/CMakeFiles/CMakeDirectoryInformation.cmake" is newer than depender "/home/vail/Development/helloworld/.build-js/CMakeFiles/helloworld.dir/depend.internal".
Scanning dependencies of target helloworld
make[2]: Leaving directory `/home/vail/Development/helloworld/.build-js'
make -f CMakeFiles/helloworld.dir/build.make CMakeFiles/helloworld.dir/build
make[2]: Entering directory `/home/vail/Development/helloworld/.build-js'
/usr/bin/cmake -E cmake_progress_report /home/vail/Development/helloworld/.build-js/CMakeFiles 1
[100%] Building CXX object CMakeFiles/helloworld.dir/helloworld.c.o
/home/vail/Development/emscripten/tools/emmaken.py     -o CMakeFiles/helloworld.dir/helloworld.c.o -c /home/vail/Development/helloworld/helloworld.c
emmaken.py:  /home/vail/Development/emscripten/tools/emmaken.py -o CMakeFiles/helloworld.dir/helloworld.c.o -c /home/vail/Development/helloworld/helloworld.c
emmaken.py:  /home/vail/Development/emscripten/tools/emmaken.py -o CMakeFiles/helloworld.dir/helloworld.c.o -c /home/vail/Development/helloworld/helloworld.c
Running: /home/vail/Development/llvm-gcc-4.2-2.9.source/cbuild/install/bin/llvm-gcc -o CMakeFiles/helloworld.dir/helloworld.c.o -c /home/vail/Development/helloworld/helloworld.c -m32 -U__i386__ -U__x86_64__ -U__SSE__ -UX87_DOUBLE_ROUNDING -UHAVE_GCC_ASM_FOR_X87 -emit-llvm -c
/home/vail/Development/helloworld/helloworld.c:1:17: error: cmath: No such file or directory
/home/vail/Development/helloworld/helloworld.c:2:18: error: limits: No such file or directory
make[2]: *** [CMakeFiles/helloworld.dir/helloworld.c.o] Error 1
make[2]: Leaving directory `/home/vail/Development/helloworld/.build-js'
make[1]: *** [CMakeFiles/helloworld.dir/all] Error 2
make[1]: Leaving directory `/home/vail/Development/helloworld/.build-js'
make: *** [all] Error 2

[paleozogt]

I think the solution here is to have some kind of c++/c shim file. emmaken_cxx.py and emmaken_c.py that call through to the underlying emmaken.py script.

[kripken]

The attachments work fine over here.

From your log, I suspect the problem is

error: cmath: No such file or directory

etc. That is, missing header files or improper include directories set up?

[kripken]

IRC discussion cleared up my misunderstanding.

Fixed in 85cba40