memcheck/tests/varinfo4.c

   1
   2 /* A small demo of providing descriptions of structured types in error
   3    messages. */
   4
   5 /* Relevant compile flags are:
   6
   7    -Wall -g -I$prefix/include/valgrind
   8
   9    eg -Wall -g -I`pwd`/Inst/include/valgrind
  10 */
  11
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <assert.h>
  15 #include "memcheck/memcheck.h"
  16
  17 /* Cause memcheck to complain about the address "a" and so to print
  18    its best guess as to what "a" actually is.  a must be
  19    addressible. */
  20
  21 void croak ( void* aV )
  22 {
  23   char* a = (char*)aV;
  24   char* undefp = malloc(1);
  25   char saved = *a;
  26   assert(undefp);
  27   *a = *undefp;
  28   (void) VALGRIND_CHECK_MEM_IS_DEFINED(a, 1);
  29   *a = saved;
  30   free(undefp);
  31 }
  32
  33 #include <stdio.h>
  34 #include <string.h>
  35
  36 typedef struct { short c1; char* c2[3]; } XX;
  37
  38 typedef
  39    struct _str { int bing; int bong; XX xyzzy[77]; }
  40    Str;
  41
  42 __attribute__((noinline))
  43 int blah ( int x, int y )
  44 {
  45   Str a[10];
  46   memset(a, 0, sizeof(a));
  47   croak(1 + (char*)(&a[3].xyzzy[x*y].c1));
  48   croak( (char*)(&a[5].bong) );
  49   croak( 1 + (char*)(&a[3].xyzzy[x*y].c2[2]) );
  50   memset(a, 0, sizeof(a));
  51   return a[3].xyzzy[x*y].c1;
  52 }
  53
  54 int main ( void )
  55 {
  56   printf("answer is %d\n", blah(3,7) );
  57   return 0;
  58 }