showcode "Compiling FB with Emscripten" - FreeBASIC Wiki Manual | FBWiki

{{fbdoc item="title" value="Compiling FB with Emscripten"}}----

{{fbdoc item="section" value="Build FB and a program on Windows for Emscripten"}}

{{fbdoc item="subsect" value="Prerequisites"}}
- git installed
- development environment for fbc, rtlib, & gfxlib2
- understand PATH environment variable
- comfortable using a command prompt
- build of latest fbc (that includes latest changes)

{{fbdoc item="subsect" value="Install Emscripten (on Windows)"}}
d:/emsdk.git is assumed for installation directory
%%
d:
cd \
git clone https://github.com/emscripten-core/emsdk.git emsdk.git
cd emsdk.git
emsdk install latest
emsdk activate latest
emsdk_env.bat
%%

{{fbdoc item="subsect" value="Build FBC libraries (on Windows)"}}
d:/fb.git is assumed for latest fbc checked out from repository
%%
d:
cd \fb.git

REM whatever you use to set-up your fbc build environment (sets PATH)
call c:\batch\setpath.bat fbgit32

REM add-in the emscripten build environment (also sets PATH)
call d:\emsdk.git\emsdk_env.bat

REM build the rtlib and gfxlib for emscripten
make rtlib gfxlib2 TARGET=asmjs-unknown-emscripten ENABLE_STANDALONE=1
%%

{{fbdoc item="subsect" value="Hook for 'emcc.bat' (on Windows)"}}
Here's the issue: fbc expects the supporting tools to be executable and emscripten font-end on windows uses 'emcc.bat' (plus python in the background) and fbc can't directly call a .BAT file. Here's a cheap hack to make it work:
Compile the following source and copy 'emcc.exe' to 'd:/fb.git/bin/js-asmjs/emcc.exe'
%%
'' emcc.exe to call emcc.bat and pass all arguments
''
'' tested, but not well tested...
''
function EscapeArg( byref arg as const string ) as string
dim ret as string = """"

for i as integer = 1 to len(arg)
select case mid( arg, i, 1 )
case """"
ret &= """"""
case else
ret &= mid( arg, i, 1 )
end select
next

ret &= """"

function = ret

end function

dim cmd as string = "emcc.bat"

dim i as integer = 1
while( command(i) > "" )
cmd += " " & EscapeArg( command(i) )
i += 1
wend

'' assumes 'emcc.bat' is on PATH

var result = shell( cmd )

end result
%%

%%
fbc emcc.bas
copy emcc.exe d:\fb.git\bin\js-asmjs\emcc.exe
%%

{{fbdoc item="subsect" value="Build an FBC program from fbc source"}}
The first time this runs, emcc takes a long time because emscripten needs to build it's own runtime library and store the result. After the first time, compile times should be much quicker.

%%
REM whatever you use to set-up your fbc build environment (sets PATH)
call c:\batch\setpath.bat fbgit32

REM add-in the emscripten build environment (also sets PATH)
call d:\emsdk.git\emsdk_env.bat

REM build program.bas
fbc -target js-asmjs program.bas
%%

{{fbdoc item="subsect" value="Run 'program.html'"}}
In the directory where 'program.html', 'program.js' & 'program.wasm' was created

Start a server:
##> python -m http.server##

Then, browse to the directory:
##http://localhost:8000/##

Or the program:
##http://localhost:8000/program.html##



{{fbdoc item="back" value="DevToc|FreeBASIC Developer Information"}}
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