How to set gcc flags in Emscripten - gcc

Question

I compile with the following command:
gcc -Wall -march=native -O3 -ffast-math -I/usr/local/include -I/usr/local/include -o waon main.o notes.o midi.o analyse.o fft.o hc.o snd.o -L/usr/local/lib -L/usr/local/lib -lfftw3 -L/usr/local/lib -lsndfile -lm
I now would like to compile with Emscripten. How do I convert the above gcc command into an emcc command?

Answer 1

The command you have described in the question is linking rather than compiling. However in general you should just be able to replace gcc with emcc and it will do the right thing. In this case you will need to replace not only this linking command but also the commands used to compile the sources to the .o files.
It would probably be a good idea to take out the -march option.
It looks like your project is using libsndfile and FFTW. You will probably need to compile these libraries yourself using emscripten. Both of them are using autotools so with a bit of luck you can compile them with emscripten simply by adding the following parameters when you run the configure script:
./configure --prefix=$HOME/emscripten-libs CC=emcc
make && make install
Then when you link your program you can specify -L$HOME/emscripten-libs/lib instead of -L/usr/local/lib.

Answer 2

Make research about emsdk download&setup on your computer.
Download emsdk instruction
Next interest link is :
emcc or em++ instruction
https://emscripten.org/docs/tools_reference/emcc.html
When you setup emcc in command line you can see this project (i make emcc final look based on python script runner.py etc.):
c-cpp-to-javascript
Basic and useful example's :
Pretty analog with gcc :
Args:
-lGL for openGL
-s TOTAL_MEMORY=512MB --memory-init-file 1 Memory staff
--preload-file folderWithImages/--use-preload-plugins If you use assets
-I forInclude/someheader.h
-L libraryFolder/someLib.lib
-std=c11
Simple run:
./emcc -O2 a.cpp -o a.js
or
./emcc -O2 a.cpp -o a.html
Links:
./emcc -O2 a.cpp -o a.bc
./emcc -O2 b.cpp -o b.bc
./emcc -O2 a.bc b.bc -o project.js
Or :
to get JS
emcc -s WASM=1 myAdds.a myLib.a source1.c source2.cpp -o build.js
to get html
emcc -s WASM=1 myAdds.a myLib.a source1.c source2.cpp -o build.html
Link together the bitcode files:
emcc project.bc libstuff.bc -o allproject.bc
Compile the combined bitcode to HTML
emcc allproject.bc -o final.html
Important note :
You can't take an existing .a library and convert it. You must build lib with emcc also.