It’s perfectly safe to use realloc. It is the way to reallocate memory in a C program. However you should always check the return value for an error condition. Don’t fall into this common trap: p = realloc(p, new_size); // don’t do this! If this fails, realloc returns NULL and you have lost access to … Read more
Don’t worry about the old contents. The correct way to use realloc is to use a specific pointer for the reallocation, test that pointer and, if everything worked out ok, change the old pointer int *oldpointer = malloc(100); /* … */ int *newpointer = realloc(oldpointer, 1000); if (newpointer == NULL) { /* problems!!!! */ /* … Read more
If realloc() fails it returns NULL. So if you do (and assuming realloc() would fail) result = realloc(result, …); result will be assigned NULL and what it pointed to is not free()ed and the address to be free()ed is lost. To fix this do: { void * tmp = realloc(result, …); if (NULL == tmp) … Read more
This error occurs because some other part of your code has corrupted the heap. We can’t tell you what that error is without seeing the rest of the code. The fact that FINE 7 is not printed tells you that realloc is failing. And that failure must be because buffer is invalid due to a … Read more
Let’s take a little closer look at memcpy and, while we’re at it, at “big O” or Landau notation. First, big-O. As i’ve talked about elsewhere, it’s worth remembering the definition of big O, which is that some function g(n) is said to be O(f(n)) when there exists a constant k for which g(n) ≤ … Read more
You can only realloc that which has been allocated via malloc (or family, like calloc). That’s because the underlying data structures that keep track of free and used areas of memory, can be quite different. It’s likely but by no means guaranteed that C++ new and C malloc use the same underlying allocator, in which … Read more
No, you won’t have a memory leak. realloc will simply mark the rest “available” for future malloc operations. But you still have to free myPointer later on. As an aside, if you use 0 as the size in realloc, it will have the same effect as free on some implementations. As Steve Jessop and R.. … Read more
From: http://www.sgi.com/tech/stl/alloc.html This is probably the most questionable design decision. It would have probably been a bit more useful to provide a version of reallocate that either changed the size of the existing object without copying or returned NULL. This would have made it directly useful for objects with copy constructors. It would also have … Read more
The standard technique is to introduce a new variable to hold the return from realloc. You then only overwrite your input variable if it succeeds: tmp = realloc(orig, newsize); if (tmp == NULL) { // could not realloc, but orig still valid } else { orig = tmp; }
When std::vector<T> runs out of capacity it has to allocate a new block. You have correctly covered the reasons. IMO it would make sense to augment the allocator interface. Two of us tried to for C++11 and we were unable to gain support for it: [1] [2] I became convinced that in order to make … Read more