Reproducing GDB hanging on reading a shared library from memory-mapped file

build.sh

#!/bin/bash

gcc -fPIC -shared -g lib.c -o lib.so
gcc -DLOAD_FROM_FILE main.c -g -o from_file
gcc main.c -g -o from_memory

lib.c

int foo(int x)
{
  int var = 0;

  return 0;
}

main.c

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>

#define _GNU_SOURCE
#include <unistd.h>
#include <dlfcn.h>
#include <sys/mman.h>
#include <sys/types.h>

int main(int argc, char ** argv)
{
  const char* path = "lib.so";
  // Receive code information
  FILE* file = fopen(path, "rb");
  assert(file);
  fseek (file, 0 , SEEK_END);
  size_t size = ftell(file);
  rewind(file);

  int fd = memfd_create("libfunction", 0);
  assert(fd > 0);
  int ret = ftruncate(fd, size) ;
  assert(ret == 0);

  void* memory_handle = mmap(NULL, size, PROT_WRITE, MAP_SHARED, fd, 0);
  assert(memory_handle);
  size_t bytes_read = fread(memory_handle, 1, size, file);
  assert(bytes_read == size);
  fclose(file);

  msync(memory_handle, size, MS_SYNC);

  char buf[32];
  snprintf(buf, 32, "%s%d", "/proc/self/fd/", fd);
#if !defined(LOAD_FROM_FILE)
  printf("Reading from %s\n", buf);
  fflush(stdout);
  void* library_handle = dlopen(buf, RTLD_NOW);
#else
  void* library_handle = dlopen("./lib.so", RTLD_NOW);
#endif
  assert(library_handle);

  typedef int (*func_t)(int);
  func_t func = dlsym(library_handle, "foo");
  assert(func);

  func(42);

  dlclose(library_handle);
  munmap(memory_handle, size);

}