Cannot call unknown function

Question

I'm trying to compile a medium-size existing code base with emscripten. Everything currently compiles, but when I try to call it from javascript I'm getting the error:

Assertion failed: Cannot call unknown function InitHOG (perhaps LLVM optimizations or closure removed it?)

I've declared this as:

extern "C" {

void EMSCRIPTEN_KEEPALIVE InitHOG()
{ ... }

}

I'm linking the function from javascript with:

InitHog = Module.cwrap('InitHOG', 'void', []);

My code base is being compiled into libraries; the function call into the library is in my guihtml library, where the final linking command is:

emcc -o ../../../../html/debug/bidirnecessary.js ../../../../objs_html/bidirnecessary.js/debug/demos/bidirnecessary/Driver.o -lenvironments -lmapalgorithms -lalgorithms -lgraphalgorithms -lgraph -lutils -lguihtml -L../../../../html/debug -Lapps/libs -Ldemos/libs -lpthread -g

Any ideas on why it can't find my function from javascript?

Nathan S. · Accepted Answer · 2018-02-10 02:38:27Z

1

While the EMSCRIPTEN_KEEPALIVE keyword works when you are compiling a single file to .js output, it doesn't work in my makefile system where I compile individual files, use emar to make a library, and then link everything together at the end.

Instead, you need to use the -s directive to specify which functions you want to export. So, something like this works.

emcc -o ../../../../html/debug/bidirnecessary.js ../../../../objs_html/bidirnecessary.js/debug/demos/bidirnecessary/Driver.o -lenvironments -lmapalgorithms -lalgorithms -lgraphalgorithms -lgraph -lutils -lguihtml -lgui -L../../../../html/debug -Lapps/libs -Ldemos/libs -lpthread -g -s EXPORTED_FUNCTIONS="['_InitHOG', '_DoFrame', '_MouseEvent']"

answered Feb 10, 2018 at 2:38

Nathan S.

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