For --closure 2, the main issue is closure advanced requires special handing of externs, see https://developers.google.com/closure/compiler/docs/api-tutorial3
See the NO_FILESYSTEM and NO_BROWSER options for reducing code size further. We could add an option to only include code that is explicitly in EXPORTED_FUNCTIONS, even runtime support. That would take some work though. But it would be great if it were contributed. On Wed, Jun 24, 2015 at 11:27 AM, Alan deLespinasse <[email protected] > wrote: > I'm trying to compile a fairly straightforward C library into JavaScript > so I can use it in Web applications. I've got it working, but I think it's > larger than it should be. > > The library is basically math functions. I just want to call them and get > their results. They don't do I/O or anything. > > As an example, I'll use the int_sqrt function example from the > documentation > <http://kripken.github.io/emscripten-site/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html#calling-compiled-c-functions-from-javascript-using-ccall-cwrap> > : > > > int int_sqrt(int x) { > return sqrt(x); > } > > > Compiling this with -O3 results in an a.out.js file of 143k bytes. I had > thought that -O3 would automatically run the Closure Compiler to do some > minification (vaguely implied by the statement that --closure 0 is the > "default > in -O2 and below > <http://kripken.github.io/emscripten-site/docs/tools_reference/emcc.html#emcc-closure>"), > but this doesn't seem to be the case. > > After a bit more research, I settled on this command line: > > emcc -O3 hello_function.cpp --closure 1 -s > EXPORTED_FUNCTIONS="['_int_sqrt']" -s MODULARIZE=1 > > This gets it down to 80k, a huge improvement, but still rather large for > such a tiny input. I tried --closure 2, but (a) that only gets it down to > 77k, and (b) then the code no longer works. I get "Uncaught TypeError: Kc > is not a function" in the console when I try to call it from JavaScript. > > I've seen vague suggestions in various docs that --closure 2 would > "require modifications to the source". I think there may have been > something about requiring Closure type annotations. But that doesn't make > sense to me, since the source code I'm dealing with is C. > > So what's actually needed for --closure 2? > > Also, looking at the generated code, there seems to be a lot of > unnecessary stuff, even with --closure 2. For example, I see standard > library stuff like malloc, free, memset, memcpy, etc. It's true that I > might want to call those functions from my JavaScript code (in fact, for > the actual library I'm trying to use, I do need at least malloc and free), > but I thought I would need to declare such things in the EXPORTED_FUNCTIONS > variable. > > Basically what I'm asking is, is it possible to get the compiled code much > smaller? > > If the answer is "that would require more optimization in Emscripten, > which we haven't had time to implement yet", then I'm curious what it would > take. I might consider contributing. (I'm pretty experienced with > JavaScript, though new to Emscripten.) > > -- > You received this message because you are subscribed to the Google Groups > "emscripten-discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
