CODEWITHSUNDEEP
c++arraysvalgrinddynamic-memory-allocationdelete-operator
user2804865
user2804865

Reputation: 1064

valgrind: errors (mistmatched free() / delete/ delete[] )

So valgrind is giving me this error:

Mismatched free() / delete / delete []

Which is referring to the following line of code:

delete[] data[position+num];

but the error keeps appearing even after i change it to

delete data[position+num];

the data array was allocated in the following manner:

data = new char*[width];
    for (int i=0; i<width; ++i){
            data[i] = new char;
    }

I just want to delete that one column of (char **data).

Also, below that error i get the following:

Address 0x5a1c160 is 0 bytes inside a block of size 1 alloc'd

==21417==    at 0x4C2B800: operator new[](unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

Upvotes: 0

Views: 4809

Answers (1)

vsoftco
vsoftco

Reputation: 56547

Not sure what you mean by delete[] data[position+num];. Your code also looks a bit dubious: data is an array of pointers-to-char, i.e. array of C-like strings, but in the loop you allocate to each pointer a single char via data[i] = new char;. Are you sure that's what you want? Usually you allocate a bunch, data[i] = new char[some_length];.

In any case, you need to delete in reverse order of allocation:

for (int i=0; i<width; ++i){
       delete data[i]; // or delete[] data[i] if pointing to more than one char
}
delete[] data;

Or, better, don't use new and delete at all, and use standard containers like std::vector<std::string>. If you allocate more than one char, then use delete[] instead.

Upvotes: 3

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