16.9 The MP_MALLOC() functions

The mpatrol library comes with a set of alternative dynamic memory allocation functions for C. These allow it to record the type and type size of every memory allocation made through these functions, which can be very useful for debugging purposes. It also means that the alignment for each memory allocation can be determined according to its type. The following test can be found in tests/pass/test9.c.

     23  /*
     24   * Allocates 16 floats and then resizes the allocation to 8 floats and
     25   * frees them.  Then allocates 16 integers and resizes the allocation
     26   * to 32 integers before freeing them.  Finally, duplicates a string
     27   * and then frees it.
     28   */
     
     
     31  #include "mpatrol.h"
     
     
     34  int main(void)
     35  {
     36      float *f;
     37      int *i;
     38      char *s;
     
     40      MP_MALLOC(f, 16, float);
     41      MP_REALLOC(f, 8, float);
     42      MP_FREE(f);
     43      MP_CALLOC(i, 16, int);
     44      MP_REALLOC(i, 32, int);
     45      MP_FREE(i);
     46      MP_STRDUP(s, "test");
     47      MP_FREE(s);
     48      return EXIT_SUCCESS;
     49  }

If this test is compiled and linked with the mpatrol library and then run with the LOGALL option, the following output will be seen in the mpatrol log file.

     ALLOC: xmalloc (84, 64 bytes, 4 bytes) [main|test9.c|40] (float x 16)
             0x0804AC36 main+38
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     returns 0x080510E8
     
     REALLOC: xrealloc (0x080510E8, 32 bytes, 4 bytes) [main|test9.c|41] (float x 8)
             0x0804AC60 main+80
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
         0x080510E8 (64 bytes) {xmalloc:84:0} [main|test9.c|40] (float x 16)
             0x0804AC36 main+38
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     returns 0x080510E8
     
     FREE: xfree (0x080510E8) [main|test9.c|42]
             0x0804AC7F main+111
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
         0x080510E8 (32 bytes) {xrealloc:84:1} [main|test9.c|41] (float x 8)
             0x0804AC60 main+80
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     ALLOC: xcalloc (85, 64 bytes, 4 bytes) [main|test9.c|43] (int x 16)
             0x0804ACB2 main+162
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     returns 0x080510E8
     
     REALLOC: xrealloc (0x080510E8, 128 bytes, 4 bytes) [main|test9.c|44] (int x 32)
             0x0804ACDF main+207
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
         0x080510E8 (64 bytes) {xcalloc:85:0} [main|test9.c|43] (int x 16)
             0x0804ACB2 main+162
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     returns 0x080510E8
     
     FREE: xfree (0x080510E8) [main|test9.c|45]
             0x0804ACFE main+238
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
         0x080510E8 (128 bytes) {xrealloc:85:1} [main|test9.c|44] (int x 32)
             0x0804ACDF main+207
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     ALLOC: xstrdup (86, 5 bytes, 1 byte) [main|test9.c|46] (char x 5)
             0x0804AD2E main+286
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
     returns 0x080510E5
     
     FREE: xfree (0x080510E5) [main|test9.c|47]
             0x0804AD4F main+319
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33
     
         0x080510E5 (5 bytes) {xstrdup:86:0} [main|test9.c|46] (char x 5)
             0x0804AD2E main+286
             0x400A09CB __libc_start_main+255
             0x0804AB81 _start+33

As you can see, the type and number of items allocated of that type are associated with each memory allocation. The function names that are logged as having made the memory allocations are from the xmalloc() family of functions since that is how the MP_MALLOC() family of functions are implemented.