Unable to free memory after using strdup

Question

gcc 4.5.1 c89

I'm trying to free my memory. However, when I check valgrind, the memory was not freed. I am wondering what I am doing wrong.

I have the following structure:

typedef struct tag_cand_results {
    char *candidate_winners[NUMBER_OF_CANDIDATES];
} cand_results;

I create an object of this structure:

cand_results *results = NULL;

I allocate some memory for the structure.

results = calloc(1, sizeof *results);

Assign him some data

results->candidate_winners[0] = strdup("Steve Martin");
results->candidate_winners[1] = strdup("Jack Jones");

Then I try to free all the allocated memory:

free(results->candidate_winners[0]);
free(results->candidate_winners[1]);
free(results);

Just to be safe assign to NULL
results = NULL;

I get the following result from valgrind.

==8119== 72 bytes in 6 blocks are definitely lost in loss record 1 of 2
==8119==    at 0x4A05E46: malloc (vg_replace_malloc.c:195)
==8119==    by 0x3FE2E82A91: strdup (strdup.c:43)
==8119==    by 0x400E5A: main (driver.c:116)
==8119== 
==8119== 72 bytes in 6 blocks are definitely lost in loss record 2 of 2
==8119==    at 0x4A05E46: malloc (vg_replace_malloc.c:195)
==8119==    by 0x3FE2E82A91: strdup (strdup.c:43)
==8119==    by 0x400E72: main (driver.c:117)

I do not know why the memory was not freed?

Thanks so much for any suggestions,

Answer 1

If this is actually a sequence of events, then valgrind is wrong. The memory is freed.

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define NUMBER_OF_CANDIDATES 10
typedef struct tag_cand_results {
    char *candidate_winners[NUMBER_OF_CANDIDATES];
} cand_results;

int main (void) {
    cand_results *results = NULL;

    results = calloc(1, sizeof *results);

    results->candidate_winners[0] = strdup("Steve Martin");
    results->candidate_winners[1] = strdup("Jack Jones");

    free(results->candidate_winners[0]);
    free(results->candidate_winners[1]);
    free(results);

    results = NULL;

    return 0;
}

valgrind:

==9649== Memcheck, a memory error detector
==9649== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==9649== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for
         copyright info
==9649== Command: ./qq
==9649== 
==9649== 
==9649== HEAP SUMMARY:
==9649==     in use at exit: 0 bytes in 0 blocks
==9649==   total heap usage: 3 allocs, 3 frees, 64 bytes allocated
==9649== 
==9649== All heap blocks were freed -- no leaks are possible
==9649== 
==9649== For counts of detected and suppressed errors, rerun with: -v
==9649== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 13 from 8)

, . - (, ). Ubuntu Lucid (10.04), gcc 4.4.3, c89.

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gcc -std=c89 -o qq qq.c
valgrind ./qq

Answer 2

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, ( printf ( "% p",...)) strdup . : bingo!

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assert ( == saved_result);

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Answer 3

gdb , - "". , , .

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Answer 4

"72 6 ", " " " ". - (!)?