Memory leaks

Memory leaks occur if your program allocates memory and then does not free it and looses the references to that memory.

Consequences

Memory leaks can generate the following runtime errors:

memory resource exhaustion
program termination

Detecting the error

The Memory Analysis tool detects this error if Perform leak check when process exits is checked and/or Perform leak check every (ms) is set to a nonzero value under Memory Errors in the configuration. In this case, memory leaks are trapped when the program exits normally (as opposed to aborting) and/or during a routine check at the preset regular time intervals.

Information returned by the Memory Problems view

The notification for this type of memory error includes the following details:

Severity: LEAK
Description: memory leak of size nbytes
Pointer: address of the lost pointer
Trap Function: always malloc
Alloc Kind: how memory was allocated for this block (malloc, calloc, or realloc)
Location: source file and line of code where the block was allocated (e.g., main.c:59)
Count: number of blocks leaked

How to fix memory leaks

Ensure that memory is deallocated on all paths, including error paths. If you enable Record memory allocation/deallocation events under Memory Errors, you can watch the results in the Memory Events view to find unmatched allocations where a corresponding free is needed to deallocate the memory.

Example

The following code shows an example of a memory leak:

int main(int argc, char ** argv) {
  char * str = malloc(10);
  if (argc > 1) {
     str = malloc(20);
     ...
  }
  printf("Str: %s\n",str);
  free(str);
  return 0;
}