heap corruption. C

Question

I have a heap corruption and can't find what the reason. Please, can you help? I have some pieces of code where to my mind the error is located. The heap corruption is generated here (see comments below):

 free(rowPermutation);
 fclose(wFile);

So, memory allocation is here:

static int N = 2,**orderOfRows, *columnsPermutation,*tmpRowPermutation,*resultPermutation,
    *u,*v,**sourceMatrix,**patternMatrix,**auxMatrix1,*incidence,*perm;

 static FILE *wFile,*file,*patternFile;

 void allocate2dMemory() {

    int i = 0;

    sourceMatrix = (int**) malloc(N * sizeof(int *));
    auxMatrix1= (int**) malloc(N * sizeof(int *));
    orderOfRows = (int**) malloc(N * sizeof(int*));
    patternMatrix = (int**) malloc(N * sizeof(int*));
    incidence = (int*) malloc(N * sizeof(int));
    columnsPermutation = (int*) malloc(N * sizeof(int));
    tmpRowPermutation = (int*) malloc(N * sizeof(int));
    resultPermutation = (int*) malloc(N * sizeof(int));
    perm = (int*)malloc(N * sizeof(int));

    u = (int*) malloc(N * sizeof(int));
    v = (int*) malloc(N * sizeof(int));

    if ((sourceMatrix == NULL) || (auxMatrix1 == NULL) || (incidence == NULL) || (orderOfRows == NULL) || 
            (columnsPermutation == NULL) || (tmpRowPermutation == NULL) || (u == NULL) || (v == NULL) || (resultPermutation == NULL)) {
            fprintf(stderr, "out of memory\n");
            exit(2);
    }


    for (i = 0; i < N; i++) {
            sourceMatrix[i] = (int*) malloc(N * sizeof(int));
            auxMatrix1[i] = (int*) malloc(N * sizeof(int));
            patternMatrix[i] = (int*) malloc(N * sizeof(int));
            incidence[i] = 0;
            if ((sourceMatrix[i] == NULL) || (auxMatrix1[i] == NULL) || (patternMatrix[i] == NULL) ) {
                            fprintf(stderr, "out of memory\n");
                            exit(2);
            }
    }

}

Open files:

 void openFile(char* filename) {
    if ((file = fopen(filename, "r")) == NULL) {
            perror("Open error");
            printf("\nPress any key for exit\n\n");
            getch();
            exit(1);
    }


    if ((patternFile = fopen("pattern.dat", "r")) == NULL) {
            perror("Open error");
            printf("\nPress any key for exit\n\n");
            getch();
            exit(1);
    }

    if ((wFile = fopen("out.txt", "w")) == NULL) {
            perror("Open error");
            printf("\nPress any key for exit\n\n");
            getch();
            exit(1);
    }

Then I close some of them ("wFile" is the file for writing):

  fclose(file);
  fclose(patternFile);

Change rows order:

  void changeRowOrder(int *computation,int **matr) {

    fprintf(wFile,"Make row permutation\n");

    int i,j;

    for (i = 0; i < N; ++i) {
            orderOfRows[computation[i]] = matr[i];
    }
    fputs("\n",wFile);
}

Change the order of columns:

   int **destMatrix = (int**) malloc(N * sizeof(int *));

    if ((destMatrix == NULL)) {
            fprintf(stderr, "out of memory\n");
            exit(2);
    }

    for (i = 0; i < N; i++) {
            destMatrix[i] = (int*) malloc(N * sizeof(int));

            if (destMatrix[i] == NULL) {
                    fprintf(stderr, "out of memory\n");
                    exit(2);
            }
    }

    for(i = 0; i < N; ++i) {
            // save permutation
            resultPermutation[perm[i]] = i;
            for(j = 0; j < N; ++j) {
                    destMatrix[i][j] = orderOfRows[i][perm[j]];
            }
    }

    fprintf(wFile,"Now result permutation is: \n");
    printArray(resultPermutation);

    for(i = 0; i < N; ++i) {
            free(sourceMatrix[i]);
    }
    free(sourceMatrix);

    sourceMatrix = destMatrix;

I need static pointers to see them in all my programm. Here is located another code where an error can exist:

The code below is at the beginning of the programm.

    int res,i,j;
    char c[25],f[25],g;

    int *rowPermutation = (int*)malloc(N*sizeof(int));

    openFile("inb.dat");
    fscanf(file,"%s %s %d %d",&c,&f,&N,&i);
    allocate2dMemory();
    getMaxtrix();
    // and so on ...
     free(rowPermutation);
    fclose(wFile);

I don't allocate memory in other place of my programm. I have noticed that memory is corrupted in the "columnsPermutation" array. First, i copy some elements, then the element begin to change. I have noticed it when I used STL container to fix heap corruption (just to know why the arrays differ).

Please,can you find an error? To my mind, I allocate the memory correctly.

enter image description here

Can you give us the exact error on output? Have you tried using GDB to find anything? Also, can you post the entire functions, not just snippets? — samoz, Jan 09 '12 at 20:17
Tangential comment: [You should prefer](http://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc) `x = malloc(N * sizeof(*x))` to `x = (T *) malloc(N * sizeof(T))`. — Oliver Charlesworth, Jan 09 '12 at 20:21
There is a possible typo at the beginning of your program. Is it possible that your function name is `getMatrix` and not `getMaxtrix`? — Marlon, Jan 09 '12 at 20:23
Problem more likely to be the code that writes to these arrays than the allocation. — David Heffernan, Jan 09 '12 at 20:30
@oli-charlesworth, you're right, but `malloc` is sometimes defined as returning `char *`, which forces people to cast. But avoiding a cast is always better, if possible. — ugoren, Jan 09 '12 at 20:30
@ugoren If `malloc` is declared as returning `char*` then that's an error. Real compilers and libraries don't do that. — David Heffernan, Jan 09 '12 at 20:32
@ugoren: Indeed, but that's pre-standard C, so I wouldn't bother too much with that... — Oliver Charlesworth, Jan 09 '12 at 20:34
You don't really need static variables. You can put them in a struct and pass them around as parameters to functions. — David Heffernan, Jan 09 '12 at 20:39
@OliCharlesworth: You should have a bot automatically post that comment in every [C] question with that pattern! — tomlogic, Jan 09 '12 at 20:45
We miss some stuff from your code to be able to tell (e.g. where is matr, perm, ... etc are allocated/initialized/set). Would you mind posting your whole C file on a pastebin somewhere or here? — Quentin Casasnovas, Jan 09 '12 at 20:55
@auxv: No, the OP should debug this, and then come back with a specific question once (s)he's isolated the problem (using GDB+Valgrind or equivalent). Posting a whole bunch of code and then asking "where's the bug?" is not a suitable question for SO... — Oliver Charlesworth, Jan 09 '12 at 21:06

score 2 · Answer 1 · answered Jan 09 '12 at 20:35

2

What is the value of N when you call the malloc() for rowPermutation? Because I see you're getting the value of N from the fscanf() after allocating memory to rowPermutation using malloc() for N elements. If N is not properly initialized, it may contain a garbage value.

int *rowPermutation = (int*)malloc(N*sizeof(int));
// What is the value of N when executing the above code?

openFile("inb.dat");
fscanf(file,"%s %s %d %d",&c,&f,&N,&i);
// N is obtained after malloc'ing memory to rowPermutation

OTOH, it is good to use tools like valgrind to check for memory leak issues.

answered Jan 09 '12 at 20:35

Sangeeth Saravanaraj

16,027
21
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see the code attentively, static N = 2; – user565447 Jan 10 '12 at 05:08
@user565447 apologies.. I may have missed it. You code was split into multiple chunks.. N was initialized in the first block and the `malloc()` and `free()` for `rowPermutation` was done in the last block. OTOH, did you get a chance to use valgrind to check the memory leak?! – Sangeeth Saravanaraj Jan 10 '12 at 05:12
thanks for comment, I haven't done it. The reason is that I use OS windows.Is there any profiles like this for windows, because I haven't UNIX in the laboratory – user565447 Jan 10 '12 at 05:23
@user565447 If you are using `windows`, then please use [cygwin](http://www.cygwin.com/) (`Cygwin` is a collection of tools which provide a `Linux` look-and-feel environment for `Windows`) and then you can install `valgrind` in that! – Sangeeth Saravanaraj Jan 10 '12 at 05:50

cateof · Answer 2 · 2012-01-09T20:51:47.953

Even for the best programmers mistakes related to heap corruption are common. Instead of going line by line, I propose to download valgrind from valgrind.org and follow a quick how to that comes with that program. Valgrdind is free and comes with the most flavors of Linux.

A commercial alternative is insure++ from parasoft.com.

Production code should always be checked against memory problems, thereafter it is a good opportunity to install a tool for that reason.

Regarding your program:

if ((sourceMatrix[i] == NULL) || (auxMatrix1[i] == NULL) || (patternMatrix[i] == NULL) ) {

If some of those pointers is NULL you are exiting. Before calling exit(2) you need to free pointers that are already allocated. Every time an exception ( pointer == NULL ) happens you also need to take care (free) that pointers that are allocated before the exception.

Hm, will the operating system do it instead of me? I need this pointers in all my programm, but if there is an error, I give the OS an opportunity to free memory — user565447, Jan 10 '12 at 05:16

heap corruption. C

2 Answers2