Invalid free() / delete / delete[] / realloc() in __libc_freeres()

问题

I'm compiling the code with -g flag and -O0. Please see valgrind output below.

I only want to know if I can I see what is invalid freed? I only see this:

==2566== Invalid free() / delete / delete[] / realloc()
==2566==    at 0x4A21244: free (vg_replace_malloc.c:468)
==2566==    by 0x500FB7A: free_mem (in /lib64/libc-2.4.so)
==2566==    by 0x500F781: __libc_freeres (in /lib64/libc-2.4.so)
==2566==    by 0x491C719: _vgnU_freeres (vg_preloaded.c:62)
==2566==    by 0x4F4E6F4: exit (in /lib64/libc-2.4.so)
==2566==    by 0x4F3930A: (below main) (in /lib64/libc-2.4.so)
==2566==  Address 0x403ef10 is not stack'd, malloc'd or (recently) free'd
==2566==
==2566==
==2566== HEAP SUMMARY:
==2566==     in use at exit: 2,416,506 bytes in 1,844 blocks
==2566==   total heap usage: 62,683 allocs, 60,840 frees, 2,957,293 bytes allocated
==2566==
==2566== Searching for pointers to 1,844 not-freed blocks
==2566== Checked 5,445,056 bytes

The code:

int HoleInstrumentenDiffListeDB(GTree *tree)
{

  OCI_Connection* cn;
  OCI_Statement* st;
  OCI_Resultset* rs;
  if (!OCI_Initialize(err_handler, NULL, OCI_ENV_DEFAULT))
        return EXIT_FAILURE;
  char query[500];
  query[0] ='\0';
  cn = OCI_ConnectionCreate( "db", "u",  "p", OCI_SESSION_DEFAULT);
  st = OCI_StatementCreate(cn);
  strcat(query, "SELECT ...");

  OCI_ExecuteStmt(st, query);
  rs = OCI_GetResultset(st);
  int i = 1;
  int j = 0;
  char *symbolp;
  while (OCI_FetchNext(rs)){


    const char * symbolp = OCI_GetString(rs,2);
    switch ( * OCI_GetString(rs,3))
    {
      case 'N':
        insertQot(tree, symbolp, OCI_GetInt(rs, 1) );
        printf("new \n");
        break;
      case 'U':
        insertQot(tree, symbolp, OCI_GetInt(rs, 1) );
        printf("upd \n");
        break;
      case 'D':
        deleteQot(tree, symbolp);
        printf("del \n");
        break;
     }
  }
  OCI_Cleanup();
  return 1;
}

int main ()
{

  GTree* t = g_tree_new_full((GCompareDataFunc)g_ascii_strcasecmp,NULL,g_free,g_free);
  HoleInstrumentenListe(t);
  HoleInstrumentenDiffListeDB(t);
  g_tree_destroy (t);
}

回答1:

I think you should be freeing line inside the while () loop, not at the end of the for () loop. I believe getline() will only allocate memory if the first parameter is *NULL, so you are in effect using the buffer allocated by the very first call over and over again.

But it's been a long while since I wrote much C!

来源：https://stackoverflow.com/questions/22099570/invalid-free-delete-delete-realloc-in-libc-freeres

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