Encounter error on "error: undefined symbol: $GL" with Strict=1

[shinji-TH]

Hi, I have a small app compile in with the following flags

/home/yapt/emsdk/upstream/emscripten/emcc.py /home/yapt/EmscriptenTestProjSkeleton/main.cpp -g -I test_file.h -o /home/yapt/EmscriptenTestProjSkeleton/build/index.html -O0 --js-library jslibrary.js --pre-js preload.js --post-js postload.js --profiling --profiling-funcs -s ASSERTIONS=1 -s SAFE_HEAP=0 -s DEMANGLE_SUPPORT=1 -lnodefs.js -std=c++20 -D_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR -s INCLUDE_FULL_LIBRARY=1 -fstrict-aliasing -fPIC -s WASM_BIGINT=1 -pthread -s PTHREAD_POOL_SIZE=2 -s PROXY_TO_PTHREAD -s FETCH=1 -s FETCH_SUPPORT_INDEXEDDB=0 -Wno-deprecated-builtins -s WASM=1 -s ALLOW_MEMORY_GROWTH=1 -s EVAL_CTORS=0 -s MAIN_MODULE=2 -s AUTOLOAD_DYLIBS=0 -s NO_EXIT_RUNTIME=0 -s INLINING_LIMIT=1 -s FORCE_FILESYSTEM=1 --emit-symbol-map -s LEGACY_GL_EMULATION=0 -s INITIAL_MEMORY=1000MB -s ENVIRONMENT=web,worker -s USE_SDL=0 -s STRICT=1 -s ALLOW_UNIMPLEMENTED_SYSCALLS=1 -s SPLIT_MODULE=1 -s USE_ICU=1 -s EXPORTED_RUNTIME_METHODS=[allocate,writeArrayToMemory]

With the flag -s ERROR_ON_UNDEFINED_SYMBOLS=1
i would result in the following errors

wasm-ld: error: symbol exported via --export not found: glGetString

Without the flag would result in the following warnings

warning: undefined symbol: $GL (referenced by $GLFW__deps: ['emscripten_get_now','$GL','$Browser','$GLFW_Window','$allocateUTF8','$FS','$GLFW','$getWasmTableEntry'], referenced by $GLFW_Window__deps: ['$GLFW'], referenced by top-level compiled C/C++ code)
warning: undefined symbol: glGetString (referenced by glfwExtensionSupported__deps: ['glGetString','$GLFW'], referenced by top-level compiled C/C++ code)

I did some tracing and understand the errors came from the following changes: #19057

From the PR, it seem GLFW should be included unless the flag MINIMAL_RUNTIME is set as zero.
However its dependency $GL, which was define in library_webgl.js, was only included when AUTO_JS_LIBRARIES is set as 1 or MAX_WEBGL_VERSION is greater than 2. With STRICT=1, the libraries are automatically excluded and resulting in the missing symbols.

Hence wish to check with @sbc100 about it.

[sbc100]

The is working as intended. In STRICT mode (i.e. with AUTO_JS_LIBRARIES=0) you need to explicitly link any libraries that you use.

In this case I think you can just add -lGL (or -lGLESv2) to your command line).

[shinji-TH]

Noted, just finding it odd to add in -lGL when my app has no usage on any WebGL functionalities.
Thanks!!

[sbc100]

Oh I see... it looks like the GL dependency is due to GLFW. Do you know where the GLFW dependency comes from?

[sbc100]

Oh, I guess the -sINCLUDE_FULL_LIBRARY setting might be the issue. Is there some reason you are using that option?

[sbc100]

Ah yes I can repro with just that setting:

$ emcc -sSTRICT -sINCLUDE_FULL_LIBRARY test/hello_world.c
error: undefined symbol: $GL (referenced by $GLFW, referenced by $GLFW_Window, referenced by root reference (e.g. compiled C/C++ code))
warning: To disable errors for undefined symbols use `-sERROR_ON_UNDEFINED_SYMBOLS=0`
warning: GL may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
error: undefined symbol: glGetString (referenced by glfwExtensionSupported, referenced by root reference (e.g. compiled C/C++ code))
warning: _glGetString may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
Error: Aborting compilation due to previous errors
emcc: error: '/usr/local/google/home/sbc/bin/node-v20.0.0-v8-canary202302081604228b65-linux-x64/bin/node --experimental-wasm-memory64 /usr/local/google/home/sbc/dev/wasm/emscripten/src/compiler.js /tmp/tmp2i5y0reu.json' failed (returned 1)

[shinji-TH]

I believe the flag -sINCLUDE_FULL_LIBRARY was included due to the app is required to load side modules via dlopen....

[sbc100]

Fixed in #19935

[shinji-TH]

Thanks!!