What are the common causes and detection methods for memory leaks in C language?

What are the common causes and detection methods for memory leaks in C language?

Common Memory Leak Causes:

1. Unreleased Dynamically Allocated Memory

   c
   void leak_example() {
       int *ptr = malloc(sizeof(int) * 100);
       // Forgot to call free(ptr)
   }

2. Double Free from Repeated Deallocation

   c
   int *ptr = malloc(sizeof(int));
   free(ptr);
   free(ptr);  // Undefined behavior

3. Pointer Overwrite Causing Unreachable Memory

   c
   int *ptr = malloc(sizeof(int) * 10);
   ptr = malloc(sizeof(int) * 20);  // Original memory leaked

4. Memory Leaks in Circular References

   • Structures referencing each other forming loops
   • Reference count never reaches zero

5. Unreleased Memory in Exception Handling Paths

   • Early function returns forget to free
   • Error handling branches miss free calls

Detection Methods:

1. Valgrind Tool

   bash
   valgrind --leak-check=full --show-leak-kinds=all ./program

2. AddressSanitizer

   bash
   gcc -fsanitize=address -g program.c -o program

3. Code Review

   • Check all malloc/calloc/realloc have corresponding free
   • Review memory release on all function return paths

Prevention Measures:

• Use RAII pattern (C++ style)
• Establish memory allocation/deallocation pairing checks
• Use smart pointer wrappers (C++)
• Regular memory analysis tool checks