Fixes Poly Bridge not starting on Linux when you have e.g. Google Chrome open

polybridge_fix.c

#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <dlfcn.h>

// compile: gcc polybridge_fix.c -o polybridge_fix.so -ldl -shared -fPIC
// use: set launch command in steam to
//      LD_PRELOAD=/path/to/polybridge_fix.so %command%

static FILE* (*real_fopen64)(const char *name, const char *mode);

FILE* fopen64(const char *name, const char *mode)
{
	FILE* f = real_fopen64(name, mode);
	if(f && strncmp(name, "/proc", 5) == 0 && strstr(name, "/cmdline")) {
		char tmp[32];
		fread(tmp, sizeof(tmp), 1, f);
		if(strcmp("/proc/self/exe", tmp) == 0) { // this confuses Unity3D
			fclose(f); f = real_fopen64("/dev/null", "r");
		} else {
			fseek(f, 0, SEEK_SET);
		}
	}
	return f;
}

__attribute__((constructor))
static void init() {
	real_fopen64 = (FILE* (*)()) dlsym(RTLD_NEXT, "fopen64");
	assert(real_fopen64);
}

I had to add -fpermissive to the gcc command line to get this to build with gcc 15.
(Apart from that it worked perfectly on two different distros, and brought much joy to my nephew, and myself :) )