Debugging unexpected crashes during string manipulation in legacy C code
I'm following best practices but I'm converting an old project and Currently developing a maintenance patch for an older application that heavily relies on string processing. It uses custom functions for string manipulation that I suspect may be causing sporadic crashes in production. Here's a snippet of a function that copies one string to another: ```c void safe_str_copy(char *dest, const char *src, size_t dest_size) { if (strlen(src) >= dest_size) { // Buffer overflow risk return; } strcpy(dest, src); } ``` This function has been working fine for a while, but after reviewing crash logs, it looks like we occasionally receive a pointer to a null or uninitialized memory segment. I've added additional checks for null pointers before calling `safe_str_copy`, but the crashes still occur intermittently. I've also tried using `strncpy` to prevent buffer overflows, but Iām concerned it might not null-terminate the destination string properly in all scenarios: ```c void safe_str_copy_v2(char *dest, const char *src, size_t dest_size) { strncpy(dest, src, dest_size - 1); dest[dest_size - 1] = '\0'; // Ensure null termination } ``` Yet, even with this adjustment, we're still facing issues during the deployment. I suspect that the root cause may lie in the way strings are handled across different parts of the application. Occasionally, the function is called with an improperly allocated destination string, which leads to undefined behavior and crashes. Does anyone have insights into best practices for safely copying strings in C, especially in a legacy context? Could there be additional safeguards or alternative functions I should consider? Any pointers would be greatly appreciated! Is there a simpler solution I'm overlooking?