CODEWITHSUNDEEP
c++opencvcmakewebassemblyemscripten
TheSlyOne
TheSlyOne

Reputation: 71

emmake make command makes error when used for openCV

I am trying to make a simple application in cpp that uses openCV and compile it to wasm. I followed the documentation and tried to produce static library files *.a and the cpp file that references the opencv library as a .o file. This is where I had the error. I ran the command

after this I navigated to where my cpp file is, then ran

based on this I get the executable. It all works well here. But when I ran the following commands instead based on the documentation, I got the error.

error happens.

make: make Scanning dependencies of target gen-pkgconfig [ 0%] Generate opencv.pc [ 0%] Built target gen-pkgconfig Scanning dependencies of target ittnotify [ 0%] Building C object 3rdparty/ittnotify/CMakeFiles/ittnotify.dir/src/ittnotify/ittnotify_static.c.o In file included from /Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/3rdparty/ittnotify/src/ittnotify/ittnotify_static.c:59: /Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/3rdparty/ittnotify/src/ittnotify/ittnotify_config.h:376:12: error: implicit declaration of function 'TBB_machine_fetchadd4' is invalid in C99 [-Werror,-Wimplicit-function-declaration] return TBB_machine_fetchadd4(ptr, 1) + 1L; ^ 1 error generated. emcc: error: '/Users/atul109/MyDocuments/work/new/emscripten_playground/emsdk/upstream/bin/clang -target wasm32-unknown-emscripten -D__EMSCRIPTEN_PTHREADS=1 -DEMSCRIPTEN -fignore-exceptions -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -D__EMSCRIPTEN_major=2 -D__EMSCRIPTEN_minor__=0 -D__EMSCRIPTEN_tiny__=17 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -iwithsysroot/include/SDL --sysroot=/Users/atul109/MyDocuments/work/new/emscripten_playground/emsdk/upstream/emscripten/cache/sysroot -Xclang -iwithsysroot/include/compat -I/Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/3rdparty/ittnotify/include -I/Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/WasmBuild/3rdparty/ippicv/ippicv_lnx/icv/include -I/Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/WasmBuild/3rdparty/ippicv/ippicv_lnx/iw/include -I/Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/WasmBuild -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winconsistent-missing-override -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -Wno-deprecated-enum-enum-conversion -Wno-deprecated-anon-enum-enum-conversion -fdiagnostics-show-option -pthread -Qunused-arguments -ffunction-sections -fdata-sections -fvisibility=hidden -fvisibility-inlines-hidden -Wno-implicit-fallthrough -Wno-undef -Wno-sign-compare -O3 -DNDEBUG -DNDEBUG -fPIC -c -pthread /Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/3rdparty/ittnotify/src/ittnotify/ittnotify_static.c -o CMakeFiles/ittnotify.dir/src/ittnotify/ittnotify_static.c.o' failed (1) make[2]: *** [3rdparty/ittnotify/CMakeFiles/ittnotify.dir/src/ittnotify/ittnotify_static.c.o] Error 1 make[1]: *** [3rdparty/ittnotify/CMakeFiles/ittnotify.dir/all] Error 2 make: *** [all] Error 2 emmake: error: 'make' failed (2)

From what I understand the ittnotify is causing error. But somehow it was fine when I did the normal cmake and make. It only does this for emcmake cmake and emmake make.

/Users/atul109/MyDocuments/work/new/emscripten_playground/opencv-3.4.14/3rdparty/ittnotify/src/ittnotify/ittnotify_config.h:376:12: error: implicit declaration of function '__TBB_machine_fetchadd4' is invalid in C99 [-Werror,-Wimplicit-function-declaration] return __TBB_machine_fetchadd4(ptr, 1) + 1L; ^ 1 error generated.

Please help.

Upvotes: 0

Views: 871

Answers (1)

sbc100
sbc100

Reputation: 3032

Emscripten is little more strict that other compiler WRT to implicit function declarations.

See https://github.com/emscripten-core/emscripten/blob/4e35687f2dca1171eca0735820d4f7f5ac65f363/emcc.py#L837-L842

You can pass -Wno-error=implicit-function-declaration to the compiler to override this, as long as you are aware that it can lead to potential signature mismatches later down the line.

Ideally you would instead fix the upstream code to avoid the implicit declarations.. but that isn't always an option.

Upvotes: 0

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