SDL_Process created with pipe_stdio set to true hangs on large output.

[failedev17]

int main(){
    const char* args[] {"clang++", "--help", nullptr};
    SDL_Process* p = SDL_CreateProcess(args, true);
    SDL_WaitProcess(p, true, nullptr);
    SDL_DestroyProcess(p);
}

Side note, Using SDL_ReadIO and SDL_LoadFile_IO on p.stream before and after flushing/closing doesn't give the output that was written to the file. I don't know if this is intended or not.

	Process p;
	p.stream = SDL_IOFromFile("temp.txt", "w+b");
	SDL_PropertiesID props = SDL_CreateProperties();
	SDL_SetPointerProperty(props, SDL_PROP_PROCESS_CREATE_ARGS_POINTER, (void *)args.data());
	SDL_SetNumberProperty(props, SDL_PROP_PROCESS_CREATE_STDOUT_NUMBER, SDL_PROCESS_STDIO_REDIRECT);
	SDL_SetPointerProperty(props, SDL_PROP_PROCESS_CREATE_STDOUT_POINTER, p.stream);
	p.process = SDL_CreateProcessWithProperties(props);
	if(!p.process){
		printf("%s\n", SDL_GetError());
	}
	SDL_DestroyProperties(props);

OS : Windows 10.

[madebr]

Your code also blocks on Linux.
clang's help is very long and will fill the pipe buffer (64kiB on Linux).
What's happening is that the kernel suspends the process (because write(2) is a blocking write) until the pipe buffer is drained.

Use SDL_ReadProcess to read all stdout in one go:

#include <SDL3/SDL.h>
int main(){
    const char* args[]= {"clang++", "--help", NULL};
    SDL_Process *p = SDL_CreateProcess(args, true);
    int ec;
    size_t s;
    void *d = SDL_ReadProcess(p, &s, &ec);
    SDL_Log("Got %p s=%u", d, (unsigned int)s);
    SDL_Log("%s", (const char *)d);
    SDL_free(d);
    SDL_WaitProcess(p, true, NULL);
    SDL_DestroyProcess(p);
    return 0;
}

Alternatively, you read chunks of data when it becomes available as long as the process is alive:

#include <SDL3/SDL.h>
int main(){
    const char* args[]= {"clang++", "--help", NULL};
    SDL_Process *p = SDL_CreateProcess(args, true);
    SDL_IOStream *clang_output = SDL_GetProcessOutput(p);
    
    while (!SDL_WaitProcess(p, false, NULL)) {
      char buffer[4096];
      size_t nb = SDL_ReadIO(clang_output, buffer, sizeof(buffer)-1);
      buffer[nb] = '\0';
      if (nb) {
        SDL_Log("nb=%u", (unsigned)nb);
        SDL_Log("Got %s", buffer);
      }
    }
    int rc;
    SDL_WaitProcess(p, true, &rc);
    SDL_Log("rc=%d", rc);
    SDL_DestroyProcess(p);
    return 0;
}

[failedev17]

Thanks for the info. I guess it should be mentioned in the SDL_WaitProcess docs somewhere. I thought what I had to do was, SDL_WaitProcess() then do a SDL_ReadProcess() and not the other way around.

[madebr]

The process subsystem is relatively very prone to a deadlock. My code above would lock when clang would read from stdin (close stdin of the subprocess after startup to avoid this. I have to check myself now what would happen if a subprocess opens /dev/tty after having closed stdin)
You need to code very careful to avoid this.

You're right about the docs.