4
votes
Accepted
Invalid pointer error when using free()
The problem lies in fread(&storage, sizeof(char), 1, old_file); This line is storing the data read directly in the pointer, overwriting the address of the malloc'd memory. It isn't storing the ...
- 68.4k
2
votes
Accepted
PSET5 compiles but gives: "free(): double free detected in tcache 2" error on testing
This is a great lesson that a problem in one place is caused by a bug somewhere else. While the code in unload is mostly correct (there is a small flaw), the data that it's processing is flawed.
If ...
- 68.4k
1
vote
Accepted
Pset 5: Speller - Double free or corruption (fasttop) error
Let's look carefully at this one. First, one has to figure out where the error occurs. Valgrind shows it to be line 148 in unload.
node *tmp = table[i]->next;
Since this isn't a free() ...
- 68.4k
1
vote
Accepted
Week 4 lecture: calling free() after malloc() removes destination contents
It seems that maybe you haven't grasped the exact purpose of the free() function. Yes, it needs to be called at some point after a malloc call. BUT, not before the code is done using the memory.
When ...
- 68.4k
1
vote
Accepted
Is vmware free or chargeable?
As an alternative, you might try the open source VirtualBox, available at https://www.virtualbox.org/wiki/Downloads. It handles the CS50 appliance well.
- 84
1
vote
Accepted
pset5 - speller "double free detected" when I run check 50 but program does nothing during self tests
This is a bug well hidden in plain sight. ;-) If you traced the program in debug, it runs all the way through to the unload() function, inside the while loop. It's failing when it hits the end of the ...
- 68.4k
1
vote
Accepted
Lab5 free_family function
The various branches are mutually exclusive. Only one of them will execute the way you've written it. But you want to free both the parents and the person.
And why check for NULL here?
else if(p->...
1
vote
Accepted
Struggling with PSET5 Speller valgrind problems (& possibly more)
I see a few problems in the code that are causing problems.
First, table[] is not initialized. That means that all the pointers in the array contain garbage data instead of NULL when the program ...
- 68.4k
1
vote
Accepted
Speller program runs accurately with memory leaks. When I add free() to correct memory leak, program stops executing
You cannot free the memory in load because it needs to be used throughout the entire program. It needs to wait until the program is done and then can be freed in unload.
It also appears that you have ...
- 68.4k
1
vote
Speller program runs accurately with memory leaks. When I add free() to correct memory leak, program stops executing
You shouldn't free memory in load(). That's where unload() comes in. All of the memory allocated in the code should be freed in unload() only, except very specific cases (this was answered by a mentor ...
1
vote
Accepted
Speller - not sure what's wrong
I believe the problem might be here:
for (int i = 0; i < N; i++)
{
//temp points to what table points to
temp = table[i];
//cursor points to what table points to
cursor = table[i];
...
1
vote
Accepted
pset4 speller trie segmentation fault
In unload_node, change
point = point->children[i];
unload_node(point);
to just
unload_node(point->children[i]);
You should not change point ...
- 20.9k
1
vote
Accepted
Unload works on small dictionary, but not on large? (speller.c / hash table method)
Hehe, put the word "zebra" in your small dictionary and see if it still works! ;-)
I'm assuming that hashtable[25] represents words that start with 'z'. I'll wager that your small dictionary ...
- 68.4k
1
vote
Accepted
pset5 (trie) valgrind memory leak
Without even looking at anything but this:
(if (start->child[i] != NULL))
I would ask if start actually exists at this point in the execution. I'll look at the code and edit my answer if/when I ...
- 68.4k
1
vote
Accepted
PSET4: free(): invalid next size (fast)
I think I found the answer. The main problem was that I was setting the ppixelIndex variable out of the for loop and I was incrementing it way too much. So when the first iteration for the first row ...
- 13
1
vote
Accepted
Pset5 Unload Giving Double Free or Corruption error
You have a tree structure (yes, a trie, but that's more a variation), and I don't see how you intend to free all nodes.
One misconception you seem to have is that freeing something makes the pointer ...
- 20.9k
1
vote
Accepted
How/when to free this memory? (pset6/server)
Does valgrind return the leak if it finds index.html or index.php? I would predict this indexes would leak memory only if neither of those files is "found". Generally speaking, one would not change ...
- 28k
1
vote
Accepted
check50 fails on caesar.c when using free()
It appears that check50 is using a slightly older version of the CS50 Library than the CS50 IDE is currently using. In that version, all strings created using GetString are freed for you before the ...
- 18.6k
1
vote
Pset6 - CS50. Segmentation fault for free(index)
Looks like a small memory leak in loookup. Maybe you're declaring a variable to store extension, but it's not allocated to include a null-terminator?
The indexes function looks fine. I think index is ...
- 28k
1
vote
Accepted
per valgrind: multiple invalid read and invalid write; invalid free(); "still reachable: 568 bytes in 1 blocks"
You can use your recursive function, but to do so, you need to pass the FILE* target variable by reference, rather than by value as you have done.
Recall Prof Malan's noswap.c example in Week 3. Or ...
- 18.6k
1
vote
Pset6 Indexes free() invalid next size error
sizeof (char), the sizeof operator returns the size in bytes of char, most likely to be 1, so that path_php has the same longuitud that path.
Sure you know which is the mistake that you make.
- 5,169
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