prepro is $(CPP) not $(CC) -E

[pmp-p]

see Line 75 and most Makefile eg

micropython/ports/javascript/Makefile

Line 16 in 5da60ff

CPP = clang -E

[pmp-p]

could be usefull also to have constantly preprocessor defines -D__CPP__ since preprocessor can choke on cross compiler special includes like emscripten.h on javascript port when building modules.

[dpgeorge]

I would be slightly wary of this (especially since py/mkenv.mk doesn't define CPP in terms of CROSS_COMPILE), but actually auto qstr generation already passes $(CFLAGS) directly to $(CPP) so it must work fine.

Merged in 862cc45

[pmp-p]

i was tring new build system for modules for official javascript port, javascript port Makefile does does define CROSS=0 and does not mention CROSS_COMPILE. also $(CC) should use emcc

https://emscripten.org/docs/tools_reference/emcc.html also not hacks like

micropython/ports/javascript/Makefile

Line 19 in 2f262d5

CPP += -isystem $(EMSCRIPTEN)/system/include/libc -cxx-isystem $(EMSCRIPTEN)/system/include/libcxx

emcc -E as in actually $(CC) -E is not a valid preprocessor.

some compilers defines variables that are unknown to preprocessors but user are expected to use them eg __EMSCRIPTEN__ || __ANDROID__ , prepro does not signal itself and does not get them from CFLAGS because of system include.

i'm not a C expert but even for a hobby i find that a bit messy.

[pmp-p]

@dpgeorge i get your point but I can't find a way to launch preprocessor via emcc in emscripten doc

i guess there's no other way than using raw emscripten clang and i still wonder how to handle eg "-s USE_SDL=2" or such CFLAGS parameters which forces inclusion of port specific versions that a module could require.

javascript $ emmake make V=1 CFLAGS_EXTRA="-DMODULE_EXAMPLE_ENABLED=1 -s USE_SDL=2" USER_C_MODULES=cmod
Including User C Module from cmod/example
mkdir -p build/genhdr
python3 ../../py/makeversionhdr.py build/genhdr/mpversion.h
GEN build/genhdr/mpversion.h
GEN build/genhdr/moduledefs.h
python3 ../../py/makemoduledefs.py --vpath="., ../.., cmod" example/example.c py/mpstate.c py/malloc.c py/gc.c py/pystack.c py/qstr.c py/vstr.c py/mpprint.c py/unicode.c py/mpz.c py/reader.c py/lexer.c py/parse.c py/scope.c py/compile.c py/emitcommon.c py/emitbc.c py/asmbase.c py/asmx64.c py/emitnx64.c py/asmx86.c py/emitnx86.c py/asmthumb.c py/emitnthumb.c py/emitinlinethumb.c py/asmarm.c py/emitnarm.c py/asmxtensa.c py/emitnxtensa.c py/emitinlinextensa.c py/formatfloat.c py/parsenumbase.c py/parsenum.c py/emitglue.c py/persistentcode.c py/runtime.c py/runtime_utils.c py/scheduler.c py/nativeglue.c py/stackctrl.c py/argcheck.c py/warning.c py/map.c py/obj.c py/objarray.c py/objattrtuple.c py/objbool.c py/objboundmeth.c py/objcell.c py/objclosure.c py/objcomplex.c py/objdeque.c py/objdict.c py/objenumerate.c py/objexcept.c py/objfilter.c py/objfloat.c py/objfun.c py/objgenerator.c py/objgetitemiter.c py/objint.c py/objint_longlong.c py/objint_mpz.c py/objlist.c py/objmap.c py/objmodule.c py/objobject.c py/objpolyiter.c py/objproperty.c py/objnone.c py/objnamedtuple.c py/objrange.c py/objreversed.c py/objset.c py/objsingleton.c py/objslice.c py/objstr.c py/objstrunicode.c py/objstringio.c py/objtuple.c py/objtype.c py/objzip.c py/opmethods.c py/sequence.c py/stream.c py/binary.c py/builtinimport.c py/builtinevex.c py/builtinhelp.c py/modarray.c py/modbuiltins.c py/modcollections.c py/modgc.c py/modio.c py/modmath.c py/modcmath.c py/modmicropython.c py/modstruct.c py/modsys.c py/moduerrno.c py/modthread.c py/vm.c py/bc.c py/showbc.c py/repl.c py/smallint.c py/frozenmod.c extmod/moductypes.c extmod/modujson.c extmod/modure.c extmod/moduzlib.c extmod/moduheapq.c extmod/modutimeq.c extmod/moduhashlib.c extmod/moducryptolib.c extmod/modubinascii.c extmod/virtpin.c extmod/machine_mem.c extmod/machine_pinbase.c extmod/machine_signal.c extmod/machine_pulse.c extmod/machine_i2c.c extmod/machine_spi.c extmod/modussl_axtls.c extmod/modussl_mbedtls.c extmod/modurandom.c extmod/moduselect.c extmod/moduwebsocket.c extmod/modwebrepl.c extmod/modframebuf.c extmod/vfs.c extmod/vfs_reader.c extmod/vfs_posix.c extmod/vfs_posix_file.c extmod/vfs_fat.c extmod/vfs_fat_diskio.c extmod/vfs_fat_file.c extmod/utime_mphal.c extmod/uos_dupterm.c lib/embed/abort_.c lib/utils/printf.c build/genhdr/moduledefs.h main.c mphalport.c modutime.c  > build/genhdr/moduledefs.h
GEN build/genhdr/qstr.i.last
clang -E -isystem /opt/sdk/emsdk/fastcomp/emscripten/system/include/libc -cxx-isystem /opt/sdk/emsdk/fastcomp/emscripten/system/include/libcxx -DNO_QSTR -Ibuild/tmp -m32 -Wall -Werror -I. -I../.. -Ibuild -std=c99  -O0 -DNDEBUG -fdata-sections -ffunction-sections cmod/example/example.c ../../py/mpstate.c ../../py/malloc.c ../../py/gc.c ../../py/pystack.c ../../py/qstr.c ../../py/vstr.c ../../py/mpprint.c ../../py/unicode.c ../../py/mpz.c ../../py/reader.c ../../py/lexer.c ../../py/parse.c ../../py/scope.c ../../py/compile.c ../../py/emitcommon.c ../../py/emitbc.c ../../py/asmbase.c ../../py/asmx64.c ../../py/emitnx64.c ../../py/asmx86.c ../../py/emitnx86.c ../../py/asmthumb.c ../../py/emitnthumb.c ../../py/emitinlinethumb.c ../../py/asmarm.c ../../py/emitnarm.c ../../py/asmxtensa.c ../../py/emitnxtensa.c ../../py/emitinlinextensa.c ../../py/formatfloat.c ../../py/parsenumbase.c ../../py/parsenum.c ../../py/emitglue.c ../../py/persistentcode.c ../../py/runtime.c ../../py/runtime_utils.c ../../py/scheduler.c ../../py/nativeglue.c ../../py/stackctrl.c ../../py/argcheck.c ../../py/warning.c ../../py/map.c ../../py/obj.c ../../py/objarray.c ../../py/objattrtuple.c ../../py/objbool.c ../../py/objboundmeth.c ../../py/objcell.c ../../py/objclosure.c ../../py/objcomplex.c ../../py/objdeque.c ../../py/objdict.c ../../py/objenumerate.c ../../py/objexcept.c ../../py/objfilter.c ../../py/objfloat.c ../../py/objfun.c ../../py/objgenerator.c ../../py/objgetitemiter.c ../../py/objint.c ../../py/objint_longlong.c ../../py/objint_mpz.c ../../py/objlist.c ../../py/objmap.c ../../py/objmodule.c ../../py/objobject.c ../../py/objpolyiter.c ../../py/objproperty.c ../../py/objnone.c ../../py/objnamedtuple.c ../../py/objrange.c ../../py/objreversed.c ../../py/objset.c ../../py/objsingleton.c ../../py/objslice.c ../../py/objstr.c ../../py/objstrunicode.c ../../py/objstringio.c ../../py/objtuple.c ../../py/objtype.c ../../py/objzip.c ../../py/opmethods.c ../../py/sequence.c ../../py/stream.c ../../py/binary.c ../../py/builtinimport.c ../../py/builtinevex.c ../../py/builtinhelp.c ../../py/modarray.c ../../py/modbuiltins.c ../../py/modcollections.c ../../py/modgc.c ../../py/modio.c ../../py/modmath.c ../../py/modcmath.c ../../py/modmicropython.c ../../py/modstruct.c ../../py/modsys.c ../../py/moduerrno.c ../../py/modthread.c ../../py/vm.c ../../py/bc.c ../../py/showbc.c ../../py/repl.c ../../py/smallint.c ../../py/frozenmod.c ../../extmod/moductypes.c ../../extmod/modujson.c ../../extmod/modure.c ../../extmod/moduzlib.c ../../extmod/moduheapq.c ../../extmod/modutimeq.c ../../extmod/moduhashlib.c ../../extmod/moducryptolib.c ../../extmod/modubinascii.c ../../extmod/virtpin.c ../../extmod/machine_mem.c ../../extmod/machine_pinbase.c ../../extmod/machine_signal.c ../../extmod/machine_pulse.c ../../extmod/machine_i2c.c ../../extmod/machine_spi.c ../../extmod/modussl_axtls.c ../../extmod/modussl_mbedtls.c ../../extmod/modurandom.c ../../extmod/moduselect.c ../../extmod/moduwebsocket.c ../../extmod/modwebrepl.c ../../extmod/modframebuf.c ../../extmod/vfs.c ../../extmod/vfs_reader.c ../../extmod/vfs_posix.c ../../extmod/vfs_posix_file.c ../../extmod/vfs_fat.c ../../extmod/vfs_fat_diskio.c ../../extmod/vfs_fat_file.c ../../extmod/utime_mphal.c ../../extmod/uos_dupterm.c ../../lib/embed/abort_.c ../../lib/utils/printf.c build/genhdr/moduledefs.h main.c mphalport.c modutime.c ../../py/mpconfig.h mpconfigport.h >build/genhdr/qstr.i.last
cmod/example/example.c:8:10: fatal error: 'SDL2/SDL.h' file not found
#include "SDL2/SDL.h"
1 error generated.
../../py/mkrules.mk:74: recipe for target 'build/genhdr/qstr.i.last' failed
make: *** [build/genhdr/qstr.i.last] Error 1
make: *** Deleting file 'build/genhdr/qstr.i.last'

is not that a flaw in emscripten ( not accepting -E and giving proper path to clang ) ?

[pmp-p]

it seems all libraries includes ends up in various $(EM_CACHE)/asmjs/ports-builds/*/include
looks a bit hard to inform preprocessor of those without integrating some emcc code