Crash when compiling basic code with emcc -O2

[Nicolas Bourdis]

I am trying to compile some basic test code with emcc -O2, and for a reason that I do not understand, the compilation fails at some point:

    D:\Projects\jsport>call emcc "../src/lib.cpp" -o emscripten_test-min.js -O2 -s EXPORTED_FUNCTIONS="['_testFct']" -s RESERVED_FUNCTION_POINTERS=1
    WARNING:root:generating system asset: optimizer.exe...
    Traceback (most recent call last):
      File "D:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1602, in <module>
        flush_js_optimizer_queue()
      File "D:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1505, in flush_js_optimizer_queue
        run_passes(chunks[0], title, just_split=False, just_concat=False)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1478, in run_passes
        final = shared.Building.js_optimizer(final, passes, debug_level >= 4, js_optimizer_extra_info, just_split=just_split, just_concat=just_concat)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\shared.py", line 1634, in js_optimizer
        ret = js_optimizer.run(filename, passes, NODE_JS, debug, extra_info, just_split, just_concat)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 538, in run
        return temp_files.run_and_clean(lambda: run_on_js(filename, passes, js_engine, source_map, extra_info, just_split, just_concat))
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\tempfiles.py", line 64, in run_and_clean
        return func()
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 538, in <lambda>
        return temp_files.run_and_clean(lambda: run_on_js(filename, passes, js_engine, source_map, extra_info, just_split, just_concat))
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 428, in run_on_js
        if not use_native(passes, source_map) or not get_native_optimizer():
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 182, in get_native_optimizer
        return get_optimizer('optimizer.exe', [], ignore_build_errors)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 166, in get_optimizer
        return shared.Cache.get(name, create_optimizer_cmake, extension='exe')
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\cache.py", line 41, in get
        temp = creator()
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 117, in create_optimizer_cmake
        proc = subprocess.Popen(['cmake', '-G', cmake_generator, '-DCMAKE_BUILD_TYPE='+cmake_build_type, shared.path_from_root('tools', 'optimizer')], cwd=build_path, stdin=log_output, stdout=log_output, stderr=log_output)
      File "D:\Program Files\Emscripten\python\2.7.5.3_64bit\lib\subprocess.py", line 711, in __init__
        errread, errwrite)
      File "D:\Program Files\Emscripten\python\2.7.5.3_64bit\lib\subprocess.py", line 948, in _execute_child
        startupinfo)

If I remove the O2 option, the exact same code compiles fine and can be called from Javascript.

Any idea how to fix this ?

I am on Windows 7 and using Emscripten 1.35.0 installed from emsdk-1.35.0-full-64bit.exe.

----------------------------------------------------------------------------------

The code I am trying to compile:

Lib.h:

    #ifndef LIB_H
    #define LIB_H
   
    extern "C" {
   
    typedef void (*invoke_oncomplete_callback_t)(int, const char*, const char*);
   
    void testFct(const void *arr_data_rgba, int arr_width, int arr_height, int job_id, invoke_oncomplete_callback_t callback);
   
    }
   
    #endif //LIB_H

Lib.cpp:

    #include <sstream>
    #include "lib.h"
   
    // Internal C++ library functions
    namespace impl {
   
    void testFct(const void *arr_data, int arr_width, int arr_height, int job_id, invoke_oncomplete_callback_t callback)
    {
        // Call the callback with the result
        std::stringstream ss;
        ss << "Inversion done in " << 0 << "s";
        callback(job_id, "", ss.str().c_str());
    }
   
    }    // namespace impl
   
    // Exposed C library function
    void testFct(const void *arr_data, int arr_width, int arr_height, int job_id, invoke_oncomplete_callback_t callback)
    {
        impl::testFct(arr_data, arr_width, arr_height, job_id, callback);
    }

----------------------------------------------------------------------------------

The output with EMCC_DEBUG=1:

    D:\Projects\jsport>set EMCC_DEBUG=1
    D:\Projects\jsport>call emcc "../src/lib.cpp" -o emscripten_test-min.js -O2 -s EXPORTED_FUNCTIONS="['_testFct']" -s RESERVED_FUNCTION_POINTERS=1
    DEBUG:root:PYTHON not defined in C:\Users\MyUserName/.emscripten, using "D:\Program Files\Emscripten\python\2.7.5.3_64bit\python.exe"
    WARNING:root:invocation: D:\Program Files\Emscripten\emscripten\1.35.0\\emcc ../src/lib.cpp -o emscripten_test-min.js -O2 -s EXPORTED_FUNCTIONS=['_testFct'] -s RESERVED_FUNCTION_POINTERS=1  (in D:\Projects\jsport)
    INFO:root:(Emscripten: Running sanity checks)
    DEBUG:root:compiling to bitcode
    DEBUG:root:emcc step "parse arguments and setup" took 0.00 seconds
    DEBUG:root:compiling source file: ../src/lib.cpp
    DEBUG:root:running: D:\Program Files\Emscripten\clang\e1.35.0_64bit\clang++ -target asmjs-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=35 -D__EMSCRIPTEN_tiny__=0 -Werror=implicit-function-declaration -nostdinc -Xclang -nobuiltininc -Xclang -nostdsysteminc -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\local\include -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\include\compat -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\include -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\include\emscripten -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\include\libc -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\lib\libc\musl\arch\emscripten -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\include\libcxx -O2 -mllvm -disable-llvm-optzns -std=c++03 ../src/lib.cpp -Xclang -isystemD:\Program Files\Emscripten\emscripten\1.35.0\system\include\SDL -emit-llvm -c -o C:\Users\MyUserName\AppData\Local\Temp\tmppmxhg5\lib_0.o
    DEBUG:root:emcc step "bitcodeize inputs" took 0.61 seconds
    DEBUG:root:optimizing ../src/lib.cpp
    DEBUG:root:emcc: LLVM opts: -O3 -disable-loop-vectorization -disable-slp-vectorization -vectorize-loops=false -vectorize-slp=false -vectorize-slp-aggressive=false  [num inputs: 1]
    DEBUG:root:emcc step "process inputs" took 0.12 seconds
    DEBUG:root:will generate JavaScript
    DEBUG:root:including libcxx_noexcept.a
    DEBUG:root:including libcxxabi.bc
    DEBUG:root:including libc.bc
    DEBUG:root:including dlmalloc.bc
    DEBUG:root:emcc step "calculate system libraries" took 0.05 seconds
    DEBUG:root:linking: ['C:\\Users\\MyUserName\\AppData\\Local\\Temp\\tmppmxhg5\\lib_0_1.o', 'C:\\Users\\MyUserName\\.emscripten_cache\\libcxxabi.bc', 'C:\\Users\\MyUserName\\.emscripten_cache\\libc.bc', 'C:\\Users\\MyUserName\\.emscripten_cache\\dlmalloc.bc', 'C:\\Users\\MyUserName\\.emscripten_cache\\libcxx_noexcept.a']
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\tmppmxhg5\lib_0_1.o to link
    DEBUG:root:adding object C:\Users\MyUserName\.emscripten_cache\libcxxabi.bc to link
    DEBUG:root:adding object C:\Users\MyUserName\.emscripten_cache\libc.bc to link
    DEBUG:root:adding object C:\Users\MyUserName\.emscripten_cache\dlmalloc.bc to link
    DEBUG:root:considering archive C:\Users\MyUserName\.emscripten_cache\libcxx_noexcept.a
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\string_fb1646b4.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\ios_1da97a69.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\locale_528bea5a.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\memory_8c4a4594.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\system_error_7d190770.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\mutex_50c49967.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\condition_variable_1b9bbc16.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\stdexcept_e242ef16.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\thread_b13652bb.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\future_fce87bc4.cpp.o to link
    DEBUG:root:adding object C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmprfwi8k\exception_f3e64688.cpp.o to link
    DEBUG:root:done running loop of archive C:\Users\MyUserName\.emscripten_cache\libcxx_noexcept.a
    DEBUG:root:emcc step "link" took 0.81 seconds
    DEBUG:root:saving intermediate processing steps to C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp
    DEBUG:root:(not saving intermediate C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\emcc-0-basebc.bc because deferring linking)
    DEBUG:root:emcc: LLVM opts: -strip-debug -disable-verify -internalize -internalize-public-api-list=testFct,malloc,free,__errno_location,fflush,__cxa_can_catch,__cxa_is_pointer_type -globaldce -pnacl-abi-simplify-preopt -pnacl-abi-simplify-postopt -disable-loop-vectorization -disable-slp-vectorization -vectorize-loops=false -vectorize-slp=false -vectorize-slp-aggressive=false  [num inputs: 15]
    DEBUG:root:emcc step "post-link" took 0.37 seconds
    DEBUG:root:LLVM => JS
    DEBUG:root:emscript: llvm backend: D:\Program Files\Emscripten\clang\e1.35.0_64bit\llc C:\Users\MyUserName\AppData\Local\Temp\tmppmxhg5\emscripten_test-min.bc -march=js -filetype=asm -o C:\Users\MyUserName\AppData\Local\Temp\emscripten_temp\tmp1zqxhc.4.js -emscripten-reserved-function-pointers=1 -O2
    DEBUG:root:  emscript: llvm backend took 0.236999988556 seconds
    DEBUG:root:emscript: js compiler glue
    DEBUG:root:  emscript: glue took 0.319000005722 seconds
    DEBUG:root:asm text sizes[[1463028, 17491], 5292, 200, 3702, 0, 5207, 23191, 1086, 268, 2736, 2080]
    DEBUG:root:  emscript: final python processing took 0.00999999046326 seconds
    DEBUG:root:emcc step "emscript (llvm=>js)" took 0.60 seconds
    DEBUG:root:wrote memory initialization to emscripten_test-min.js.mem
    DEBUG:root:emcc step "source transforms" took 0.05 seconds
    DEBUG:root:running js post-opts
    DEBUG:root:applying js optimization passes: asm eliminate simplifyExpressions simplifyIfs registerize minifyNames asmLastOpts last minifyWhitespace cleanup
    chunkification: num funcs: 707 actual num chunks: 3 chunk size range: 522935 - 450885
    WARNING:root:generating system asset: optimizer.exe...
    DEBUG:root:building native optimizer via CMake: optimizer.exe
    Traceback (most recent call last):
      File "D:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1602, in <module>
        flush_js_optimizer_queue()
      File "D:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1505, in flush_js_optimizer_queue
        run_passes(chunks[0], title, just_split=False, just_concat=False)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1478, in run_passes
        final = shared.Building.js_optimizer(final, passes, debug_level >= 4, js_optimizer_extra_info, just_split=just_split, just_concat=just_concat)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\shared.py", line 1634, in js_optimizer
        ret = js_optimizer.run(filename, passes, NODE_JS, debug, extra_info, just_split, just_concat)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 538, in run
        return temp_files.run_and_clean(lambda: run_on_js(filename, passes, js_engine, source_map, extra_info, just_split, just_concat))
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\tempfiles.py", line 64, in run_and_clean
        return func()
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 538, in <lambda>
        return temp_files.run_and_clean(lambda: run_on_js(filename, passes, js_engine, source_map, extra_info, just_split, just_concat))
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 428, in run_on_js
        if not use_native(passes, source_map) or not get_native_optimizer():
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 182, in get_native_optimizer
        return get_optimizer('optimizer.exe', [], ignore_build_errors)
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 166, in get_optimizer
        return shared.Cache.get(name, create_optimizer_cmake, extension='exe')
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\cache.py", line 41, in get
        temp = creator()
      File "D:\Program Files\Emscripten\emscripten\1.35.0\tools\js_optimizer.py", line 117, in create_optimizer_cmake
        proc = subprocess.Popen(['cmake', '-G', cmake_generator, '-DCMAKE_BUILD_TYPE='+cmake_build_type, shared.path_from_root('tools', 'optimizer')], cwd=build_path, stdin=log_output, stdout=log_output, stderr=log_output)
      File "D:\Program Files\Emscripten\python\2.7.5.3_64bit\lib\subprocess.py", line 711, in __init__
        errread, errwrite)
      File "D:\Program Files\Emscripten\python\2.7.5.3_64bit\lib\subprocess.py", line 948, in _execute_child
        startupinfo)

[Alon Zakai]

Looks like it's failing to build the native optimizer. Based on the log, it seems it can't even find a local compiler to run (but I'm not sure how that works on windows). A more common error is if the local compiler might not have sufficient c++11 support (but then I'd expect a clearer error, however, maybe on windows it's different?). You can disable the native optimizer with EMCC_NATIVE_OPTIMIZER=0 in the env, but then things will compile more slowly. To investigate more, you might want to look inside that js_optimizer.py file.

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[Nicolas Bourdis]

Indeed, setting EMCC_NATIVE_OPTIMIZER=0 seems to fix the problem. Thanks a lot for that tip :)

Though I am surprised that this could be linked to the native compiler, as I have both VS2010 and VS2015 installed. If that is the problem, many people must have encountered it before me ? Surely I am not the first one to use release compilation with emscripten on Windows ?

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