How can a I do a synchronous fetch?

[tuket]

I have been strugling to do a synchronous download using the fetch API.

I'm not sure if it's possible because I have found some related issues that haven't been resolved:

• Synchronous Fetch API Bug with Fix #8749
• EMSCRIPTEN_FETCH_REPLACE needed for loads to memory? #8183

This is what I'm trying:

emscripten_fetch_attr_t attr;
emscripten_fetch_attr_init(&attr);
strcpy(attr.requestMethod, getCommand().c_str());
attr.attributes = EMSCRIPTEN_FETCH_LOAD_TO_MEMORY | EMSCRIPTEN_FETCH_SYNCHRONOUS; //| EMSCRIPTEN_FETCH_REPLACE;
attr.userData = this;
attr.onsuccess = callback_success;
attr.onerror = callback_error;
auto fetch = emscripten_fetch(&attr, getURL().c_str());

The returned pointer is always null.

I have seen in the documentation that there are a couple of flags that you can use. I'm currently using -sUSE_PTHREADS.

The documentation suggests using both flags:

--proxy-to-worker + -sUSE_PTHREADS: Synchronous Fetch operations are available both on the main thread and pthreads.

But if I add --proxy-to-worker, I get a compile error saying that the flags are not compatible!

em++: error: --proxy-to-worker is not supported with -s USE_PTHREADS>0! Use the option -s PROXY_TO_PTHREAD=1 if you want to run the main thread of a multithreaded application in a web worker.

I tried adding the flag -s PROXY_TO_PTHREAD=1 as well, but I get the same error.

Could you please help me?

EDIT:

After lots of trial and error, I managed to get it to compile using the following flags combination:

set(emscriptenCompilerFlags "-s USE_PTHREADS=1 -s USE_SDL=2")
set(emscriptenLinkerFlags "-s WASM=1 -s USE_PTHREADS=1 -s PROXY_TO_PTHREAD=1 -s PTHREAD_POOL_SIZE=4 -s USE_WEBGL2=1 -s MIN_WEBGL_VERSION=2 -s MAX_WEBGL_VERSION=2 -s ASSERTIONS=1 -s ALLOW_MEMORY_GROWTH=1")

However, it doesn't work when I try to run it: