C - Write access violation

Question

I have an error at the last line, in nullString, a function setting all the string to '\0' with a simple for()

void function ( unsigned char inputArray[], size_t inputSize )
{
    size_t cellSize;
    if (inputSize <= 256)
        cellSize = 1;
    else
        cellSize = ceil(inputSize / 2 / 256) + 1;


    // Sub Box
    unsigned char subBox[255];
    for (size_t line = 0; line < 255; line++)
        subBox[line] = 0;

    generate_SubBox(subBox, key);
    // Sub Box


    // Sub Box reverse
    unsigned char subBox_Inverse[255];
    for (size_t line = 0; line < 255; line++)
        subBox_Inverse[line] = 0;

    generate_SubBox_Inverse(subBox_Inverse, subBox, key);
    // Sub Box reverse        

    unsigned char* inputArray2 = NULL;
    inputArray2 = malloc(sizeof(unsigned char)* inputSize / 2);
    verifyMalloc(inputArray2);
    nullString(inputArray2, inputSize / 2);

    unsigned char string_temp[3] = { 0 };
    size_t w = 0;
    for (size_t i = 0; i < inputSize / 2; i++)
    {
        string_temp[0] = inputArray[w];
        string_temp[1] = inputArray[w + 1];

        inputArray2[i] = strtoll(string_temp, NULL, 16);

        w += 2;
    }
}

I tried neutralizing line per line all instructions coming before nullString() by commenting them but it doesn't change anything.

If I neutralize nullString, the error comes after, at

inputArray2[i] = strtoll(...)

Hope you've got the answer :)

Thanks in advance !

EDIT: Here is nullString:

void nullString(unsigned char input[], size_t length)
{
    for (size_t x = 0; x < length; x++)
        input[x] = '\0';
}

I commented all the instructions before nullString, the error is still there.

I also verified variables and they all look like good

EDIT 2: verifyMalloc:

void verifyMalloc(int* pointer)
{
    if (pointer == NULL)
    {
        perror("Erreur");

        Sleep(15000);
        exit(0);
    }
}

Probably your problem is in `nullString()` or somewhere else. Would you mind showing this function? — harper, Jun 12 '17 at 16:38
Ideas to isolate the failure: 1) inactivate all code that is not related to `inputArray2` by commenting out. If the Failure is gone look for the last change. 2) Use a debugger and verify the variables just before the location where the exception occurs. — harper, Jun 12 '17 at 16:41
This is looking like `verifyMalloc()` is failing at doing it's job (or that it's supposed to return a value and you're failing at checking that value) — SiggiSv, Jun 12 '17 at 17:28
I posted verifyMalloc, I don't really know if the function is good, especially with the pointer but it wasn't a problem before. I tried to check the allocation with a simple ( ... == NULL ) and there was no error — Tom Clabault, Jun 12 '17 at 17:38
Can you explain what you want your code to do? `inputArray2[i] = strtoll(/* ... */);` looks, without further context, a bit fishy to me. — Daniel Jour, Jun 12 '17 at 18:02
That's because inputArray contain an hexadecimal string I want to convert in decimal in inputArray2 — Tom Clabault, Jun 12 '17 at 18:45
Valgrind is not available for Windows rgiht ? I can't find it for Windows, only on Linux — Tom Clabault, Jun 12 '17 at 21:08
So is there a substitute for Valgrind available for Windows ? — Tom Clabault, Jun 12 '17 at 21:34
I used Dr. Memory to find out the issue and here is the full error given by Dr. Memory: "Error #1: UNADDRESSABLE ACCESS: writing 0x0000000042d80040-0x0000000042d80041 1 byte(s)". It's indeed at the 45th lines, where memset is — Tom Clabault, Jun 12 '17 at 21:56
Problem solved :). I didn't include it because it was already include in main.c but it seems that it had to be reinclude in Function.c. No more problem, thank you ! — Tom Clabault, Jun 12 '17 at 22:19
So this was the problem: https://stackoverflow.com/q/1230386/4766261 ? — SiggiSv, Jun 12 '17 at 22:30

score 3 · Accepted Answer · answered Jun 12 '17 at 22:46

Everything we're seeing is seriously hinting at you forgetting to #include <stdlib.h> (and ignoring the warnings resulting from that).

This is what might happens when you use malloc() without including stdlib.h in the same file:

the compiler consider the malloc() function to be declared implicitly, which means it is assuming that it's return types is int (instead of *void).
This might work when sizeof (int) is the same as sizeof (*void). But when int is 32-bits while pointers are 64-bits then the address returned by malloc() might lose half of it's bits and point to an invalid address.

Sokre · Answer 2 · 2017-06-12T20:15:42.100

Try using

void bzero(void *s, size_t n); or
void *memset(void *s, int c, size_t n);

instead of your nullString() and for()something[x]=0 loops.

Then, this does not make all of the array zeroed:

unsigned char string_temp[3] = { 0 };

This makes

string[0] = 0;
string[1] = god_knows;
string[2] = god_knows_not;

so either - unsigned char string_temp[3] = {0,0,0}; 
or bzero(string_temp,3);

Consequently, when you do this:

string_temp[0] = inputArray[w];
string_temp[1] = inputArray[w + 1];

inputArray2[i] = strtoll(string_temp, NULL, 16);

strtoll() will be guessing when to stop. No guarantee this would be at string_temp[2].

Then, this should be enough:

unsigned char* inputArray2 = malloc(sizeof(unsigned char) * inputSize / 2);

inputArray2 will be NULL if malloc failed, or a valid pointer if it succeeded.

You may want to check your inputSize / this_and_that arithmetics. Does it really deliver what you expect? You might be surprised by division result of integer operands.

This also looks suspicious:

inputArray2[i] = strtoll(string_temp, NULL, 16);

strtoll returns longlong integer but your inputArray2 is of unsigned char type. So you are trying to store 8 bytes (sizeof longlong = 8) and you reserved place only for one (sizeof char = 1)

Redeclare your inputArray2 as long long

long long *inputArray2 = malloc(sizeof(long long) * inputSize /2 );

And try this with memset():

size_t size = sizeof(long long) * inputSize/2; 
//Do you really need long long? You are storing max three digits. uint_8 will be enough

long long* inputArray2 = malloc(size);
memset(inputArray2, 0, size);

inputSize / 2 gives me the exact value i'm excepting, no problem at that level so I left inputArray2 = malloc(...) as it was Thanks for string_temp[3] = { 0 }, it's now string_temp[3] = { 0, 0, 0 } Memset ( beacause i'm under Windows 10 and Visual Studio ) does not help, same error but when executing memset. I also checked the malloc with if(... == NULL), no problem, the malloc is good... — Tom Clabault, Jun 12 '17 at 19:53
Where do you get the error now? In memset(), which you are now using instead of nullString(); Or later, when you try inputArray2[i] = strtoll(); — Sokre, Jun 12 '17 at 20:01
The error is in memset(), i don't use nullString anymore. If I comment memset(), then the error comes at "inputArray2[i] = strtoll(string_temp, NULL, 16);" — Tom Clabault, Jun 12 '17 at 20:05
"Then, this does not make all of the array zeroed: `unsigned char string_temp[3] = { 0 };`" Yes, it does. See: https://stackoverflow.com/a/2589751/4766261 — SiggiSv, Jun 12 '17 at 21:27

C - Write access violation

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