sem_open() produces internal error: mmapAlloc called but `emscripten_builtin_memalign` native symbol not exported

[inobelar]

sem_open() call produces:

internal error: mmapAlloc called but emscripten_builtin_memalign native symbol not exported

main.cpp:

#include <fcntl.h>           /* For O_* constants */
#include <sys/stat.h>        /* For mode constants */
#include <semaphore.h>       /* For sem_open(), sem_close(), sem_unlink() */

#include <stdio.h>           /* For fputs() */

int main(int argc, char** argv)
{
    fputs("sem_open()\n", stdout);

    sem_t* s = sem_open("/my_semaphore", O_CREAT, 0644, 0);
    if (s == SEM_FAILED) {
        fputs("Failed to create semaphore!\n", stdout);
        return 1;
    }

    fputs("sem_close()\n", stdout);
    sem_close(s);

    fputs("sem_unlink()\n", stdout);
    sem_unlink("/my_semaphore");

    fputs("exit\n", stdout);
    return 0;
}

Compile command:

$ emcc -v --std=c++11 -sWASM=1 -sALLOW_MEMORY_GROWTH=1 -pthread ./main.cpp -o main.html 

---

Version of emscripten/emsdk:

$ emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.34 (57b21b8fdcbe3ebb523178b79465254668eab408)
clang version 17.0.0 (https://github.com/llvm/llvm-project a031f72187ce495b9faa4ccf99b1e901a3872f4b)
Target: wasm32-unknown-emscripten
Thread model: posix

Full link command and output with -v appended:

emcc -v --std=c++11 -sWASM=1 -sALLOW_MEMORY_GROWTH=1 -pthread ./main.cpp -o main.html 
 "/home/yurii/work/emscripten/emsdk/upstream/bin/clang" --version
 "/home/yurii/work/emscripten/emsdk/upstream/bin/clang++" -target wasm32-unknown-emscripten -fignore-exceptions -fvisibility=default -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -D__EMSCRIPTEN_SHARED_MEMORY__=1 -DEMSCRIPTEN --sysroot=/home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot -Xclang -iwithsysroot/include/fakesdl -Xclang -iwithsysroot/include/compat -v --std=c++11 -pthread -matomics -mbulk-memory ./main.cpp -c -o /tmp/emscripten_temp_hzg_8tcb/main_0.o
clang version 17.0.0 (https://github.com/llvm/llvm-project a031f72187ce495b9faa4ccf99b1e901a3872f4b)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /home/yurii/work/emscripten/emsdk/upstream/bin
 (in-process)
 "/home/yurii/work/emscripten/emsdk/upstream/bin/clang-17" -cc1 -triple wasm32-unknown-emscripten -emit-obj -mrelax-all -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name main.cpp -mrelocation-model static -mframe-pointer=none -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-feature +atomics -target-feature +bulk-memory -target-feature +mutable-globals -target-feature +sign-ext -target-cpu generic -target-feature +atomics -target-feature +bulk-memory -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -v -fcoverage-compilation-dir=/home/yurii/Downloads/emsc_sem_test -resource-dir /home/yurii/work/emscripten/emsdk/upstream/lib/clang/17 -D __EMSCRIPTEN_SHARED_MEMORY__=1 -D EMSCRIPTEN -isysroot /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot -internal-isystem /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten/c++/v1 -internal-isystem /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1 -internal-isystem /home/yurii/work/emscripten/emsdk/upstream/lib/clang/17/include -internal-isystem /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten -internal-isystem /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include --std=c++11 -fdeprecated-macro -fdebug-compilation-dir=/home/yurii/Downloads/emsc_sem_test -ferror-limit 19 -fvisibility=default -pthread -fgnuc-version=4.2.1 -fcxx-exceptions -fignore-exceptions -fexceptions -fcolor-diagnostics -iwithsysroot/include/fakesdl -iwithsysroot/include/compat -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -o /tmp/emscripten_temp_hzg_8tcb/main_0.o -x c++ ./main.cpp
clang -cc1 version 17.0.0 based upon LLVM 17.0.0git default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten/c++/v1"
ignoring nonexistent directory "/home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten"
#include "..." search starts here:
#include <...> search starts here:
 /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/fakesdl
 /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/compat
 /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1
 /home/yurii/work/emscripten/emsdk/upstream/lib/clang/17/include
 /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/include
End of search list.
emcc: warning: -pthread + ALLOW_MEMORY_GROWTH may run non-wasm code slowly, see https://github.com/WebAssembly/design/issues/1271 [-Wpthreads-mem-growth]
 "/home/yurii/work/emscripten/emsdk/upstream/bin/wasm-ld" -o main.wasm /tmp/emscripten_temp_hzg_8tcb/main_0.o -L/home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten /home/yurii/work/emscripten/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/crtbegin.o -lGL-mt -lal -lhtml5 -lstubs-debug -lnoexit -lc-mt-debug -ldlmalloc-mt -lcompiler_rt-mt -lc++-mt-noexcept -lc++abi-debug-mt-noexcept -lsockets-mt -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --allow-undefined-file=/tmp/tmpvg3a51ol.undefined --import-memory --shared-memory --strip-debug --export-if-defined=main --export-if-defined=_emscripten_thread_init --export-if-defined=_emscripten_thread_exit --export-if-defined=_emscripten_thread_crashed --export-if-defined=_emscripten_tls_init --export-if-defined=pthread_self --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=__main_argc_argv --export-if-defined=fflush --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=stackSave --export=stackRestore --export=stackAlloc --export=__errno_location --export=emscripten_dispatch_to_thread_ --export=_emscripten_thread_free_data --export=emscripten_main_runtime_thread_id --export=emscripten_main_thread_process_queued_calls --export=_emscripten_run_in_main_runtime_thread_js --export=emscripten_stack_set_limits --export=__get_temp_ret --export=__set_temp_ret --export=__wasm_call_ctors --export-table -z stack-size=65536 --initial-memory=16777216 --no-entry --max-memory=2147483648 --stack-first
 "/home/yurii/work/emscripten/emsdk/upstream/bin/wasm-emscripten-finalize" --dyncalls-i64 --pass-arg=legalize-js-interface-exported-helpers main.wasm -o main.wasm --detect-features
 "/home/yurii/work/emscripten/emsdk/node/14.18.2_64bit/bin/node" /home/yurii/work/emscripten/emsdk/upstream/emscripten/src/compiler.js /tmp/tmpos_n67_b.json
 "/home/yurii/work/emscripten/emsdk/upstream/bin/llvm-objcopy" main.wasm main.wasm --remove-section=.debug* --remove-section=producers
 "/home/yurii/work/emscripten/emsdk/node/14.18.2_64bit/bin/node" /home/yurii/work/emscripten/emsdk/upstream/emscripten/tools/acorn-optimizer.js /tmp/emscripten_temp_hzg_8tcb/main.js growableHeap -o /tmp/emscripten_temp_hzg_8tcb/main.jso1.js
 "/home/yurii/work/emscripten/emsdk/node/14.18.2_64bit/bin/node" /home/yurii/work/emscripten/emsdk/upstream/emscripten/tools/preprocessor.js /tmp/emscripten_temp_hzg_8tcb/settings.js worker.js --expandMacros
 "/home/yurii/work/emscripten/emsdk/node/14.18.2_64bit/bin/node" /home/yurii/work/emscripten/emsdk/upstream/emscripten/tools/preprocessor.js /tmp/emscripten_temp_hzg_8tcb/settings.js shell.html

[sbc100]

I think this was fixed in #18905. Can you try with the tip-of-tree version of emsdk (emsdk install tot)?

[inobelar]

@sbc100 I tried 'tot' version:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.37-git (1e7b78fe45cee0b96b64938f9742368923cd0713)

Now it works (mmapAlloc error is gone) 😃

But sem_open() returns SEM_FAILED result 😞 Have no idea, is it expected behavior, or new kind of error. Techically, issue is solved, thanks :)

[sbc100]

Yes, I don't the sem_open family of function works under emscripten. We should probably simple remove them. Those functions are really designed from multi-process communication which emscripten does not support in general.