compilation - Emscripten compile C++ on macOS: error "No thread API"

Question

I'm trying to compile a relatively simple C++ program using emscripten for use in javascript (wasm). When I compile with the following settings

emcc ./lttb.cpp 
  --bind 
  --target=wasm32-unknown-unknown-wasm 
  --optimize=3 
  -v 
  -nostdlib 
  -Wl,--export-all 
  -Wl,--no-entry 
  -Wl,--allow-undefined 
  -s ALLOW_MEMORY_GROWTH=1 
  -o lttb.wasm 

I get the following error:

In file included from ./lttb.cpp:3:
In file included from /usr/local/Cellar/emscripten/2.0.12/libexec/system/include/emscripten/bind.h:14:
In file included from /usr/local/Cellar/emscripten/2.0.12/libexec/system/include/libcxx/stddef.h:39:
/usr/local/Cellar/emscripten/2.0.12/libexec/system/include/libcxx/__config:1134:6: error: "No thread API"
#    error "No thread API"

More details here

question from:https://stackoverflow.com/questions/65894506/emscripten-compile-c-on-macos-error-no-thread-api

Answer 1

Most likely you are creating thread within lttb.cpp

In that case you must add: -s USE_PTHREADS=1

It is also recommended to define in advance number of threads, e.g.: -s PTHREAD_POOL_SIZE=7