-lGL may pick up libGL.a instead of library_webgl.js

[juj]

In PR #10116, upstream mac bot gives

emcc:WARNING: invocation: /Users/distiller/project/emcc.py -o a.html /Users/distiller/project/tests/minimal_webgl/main.cpp /Users/distiller/project/tests/minimal_webgl/webgl.c --js-library /Users/distiller/project/tests/minimal_webgl/library_js.js -s RUNTIME_FUNCS_TO_IMPORT=[] -s USES_DYNAMIC_ALLOC=2 -lGL -s MODULARIZE=1 -s MINIMAL_RUNTIME=2 -s AGGRESSIVE_VARIABLE_ELIMINATION=1 -s ENVIRONMENT=web -s TEXTDECODER=2 -s ABORTING_MALLOC=0 -s ALLOW_MEMORY_GROWTH=0 -s SUPPORT_ERRNO=0 -s DECLARE_ASM_MODULE_EXPORTS=1 -s MALLOC=emmalloc -s GL_EMULATE_GLES_VERSION_STRING_FORMAT=0 -s GL_EXTENSIONS_IN_PREFIXED_FORMAT=0 -s GL_SUPPORT_AUTOMATIC_ENABLE_EXTENSIONS=0 -s GL_TRACK_ERRORS=0 -s GL_SUPPORT_EXPLICIT_SWAP_CONTROL=0 -s GL_POOL_TEMP_BUFFERS=0 -s FAST_UNROLLED_MEMCPY_AND_MEMSET=0 -s MIN_CHROME_VERSION=58 --output_eol linux -O3 --closure 1 -DNDEBUG -ffast-math  (in /private/var/folders/ms/xg67k5sn16xc7sdr_w3q45840000gn/T/emscripten_test_other_11g8vels)
shared:DEBUG: successfully executed /Users/distiller/emsdk-master/upstream/bin/clang++ --version
root:DEBUG: Checking JS engine ['/Users/distiller/emsdk-master/node/12.9.1_64bit/bin/node']
shared:DEBUG: successfully executed /Users/distiller/emsdk-master/node/12.9.1_64bit/bin/node --version
shared:DEBUG: successfully executed /Users/distiller/emsdk-master/upstream/bin/llc --version
shared:INFO: (Emscripten: Running sanity checks)
shared:DEBUG: successfully executed java -version
shared:DEBUG: successfully executed java -version
emcc:DEBUG: asm.js opts not forced by user or an option that depends them, and we do not intend to run the asm.js, so disabling and leaving opts to the binaryen optimizer
emcc:DEBUG: compiling to bitcode
emcc:DEBUG: emcc step "parse arguments and setup" took 0.32 seconds
cache:DEBUG: PID 1008 acquiring multiprocess file lock to Emscripten cache at /Users/distiller/.emscripten_cache/wasm-obj
cache:DEBUG: done
emcc:DEBUG: compiling source file: /Users/distiller/project/tests/minimal_webgl/main.cpp
shared:DEBUG: successfully executed /Users/distiller/emsdk-master/upstream/bin/clang -target wasm32-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=39 -D__EMSCRIPTEN_tiny__=5 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/Users/distiller/project/system/include/libcxx -Xclang -isystem/Users/distiller/project/system/lib/libcxxabi/include -Xclang -isystem/Users/distiller/project/system/include/compat -Xclang -isystem/Users/distiller/project/system/include -Xclang -isystem/Users/distiller/project/system/include/libc -Xclang -isystem/Users/distiller/project/system/lib/libc/musl/arch/emscripten -Xclang -isystem/Users/distiller/project/system/local/include -Xclang -isystem/Users/distiller/.emscripten_cache/wasm-obj/include -O3 -DNDEBUG -ffast-math -DEMSCRIPTEN /Users/distiller/project/tests/minimal_webgl/main.cpp -Xclang -isystem/Users/distiller/project/system/include/SDL -c -o /var/folders/ms/xg67k5sn16xc7sdr_w3q45840000gn/T/emscripten_temp/main_0.o -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr
emcc:DEBUG: compiling source file: /Users/distiller/project/tests/minimal_webgl/webgl.c
shared:DEBUG: successfully executed /Users/distiller/emsdk-master/upstream/bin/clang -target wasm32-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=39 -D__EMSCRIPTEN_tiny__=5 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/Users/distiller/project/system/include/libcxx -Xclang -isystem/Users/distiller/project/system/lib/libcxxabi/include -Xclang -isystem/Users/distiller/project/system/include/compat -Xclang -isystem/Users/distiller/project/system/include -Xclang -isystem/Users/distiller/project/system/include/libc -Xclang -isystem/Users/distiller/project/system/lib/libc/musl/arch/emscripten -Xclang -isystem/Users/distiller/project/system/local/include -Xclang -isystem/Users/distiller/.emscripten_cache/wasm-obj/include -O3 -DNDEBUG -ffast-math -DEMSCRIPTEN /Users/distiller/project/tests/minimal_webgl/webgl.c -Xclang -isystem/Users/distiller/project/system/include/SDL -c -o /var/folders/ms/xg67k5sn16xc7sdr_w3q45840000gn/T/emscripten_temp/webgl_1.o -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr
emcc:DEBUG: emcc step "compile inputs" took 0.34 seconds
emcc:DEBUG: emcc step "process inputs" took 0.00 seconds
emcc:DEBUG: looking for library "GL"
emcc:DEBUG: found library "GL" at /Users/distiller/.emscripten_cache/wasm-obj/libGL.a

i.e. -lGL picks up libGL.a from Emscripten cache. Not quite sure why the cache directory is in -L directories or how it gets there, or why it happens only on the macOS bot, but that was the cause of the bug in #10116.

[juj]

One can work around that by passing -lwebgl.js instead of -lGL.

[sbc100]

I'll take a look and see if I can find a sensible solution. Is the behavior you are expecting is that -lGL would give you both libGL native and webgl.js library?

I've been trying to make the cache directory more like a normal sysroot and less magical, which is why its in the -I and -L paths these days.

[juj]

Yeah, when linking with WebGL, both library_webgl.js and the native lib libGL.a should get picked up. (it's never one or the other, but both always come together)

[stale]

This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 30 days. Feel free to re-open at any time if this issue is still relevant.

[sbc100]

bump