[Home] memcpy SIGBUS (duh)

I just had a #FFD700 moment.

A quick Google of memcpy SIGBUS lead me on a wild goose chase about alignment errors.

However, the problem for me was an extremely simple one - the kind that you might expect -Wall -Werror should catch.

int main(int argc, char* argv[])
{
  char* str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; // 36 + 1
  memcpy(str, "abcdef", 3);

  printf("%s\n", str);
  // abcdef6789...

  return 0;
}

What's the issue here? Well, str is actually a const char* because it's loaded into read-only memory!

int main(int argc, char* argv[])
{
  const char* str_const = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; // 36 + 1
  char* str = malloc(strlen(str_const) + 1);
  memcpy(str, str_const, strlen(str_const) + 1);
  memcpy(str, "abcdef", 3);

  printf("%s\n", str);
  // abcdef6789...

  return 0;
}
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