You’re close. In C (at least since the 1989 version of the standard), the cast before malloc and realloc is unnecessary, since C can convert values of type void * to int * without a cast. This is not true for C++, so based on the error you’re getting, it sounds like you’re compiling this … Read more
No, it does not. That aspect has often annoyed me since you can’t just use: if ((buff = realloc (buff, newsize)) == NULL) return; in your code if you want to free the original on failure. Instead you have to do something like: if ((newbuff = realloc (buff, newsize)) == NULL) { free (buff); return; … 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
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
Yes, guaranteed by the C Standard if the new object can be allocated. (C99, 7.20.3.4p2) “The realloc function deallocates the old object pointed to by ptr and returns a pointer to a new object that has the size specified by size.”
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
A realloc that increases the size of the block will retain the contents of the original memory block. Even if the memory block cannot be resized in placed, then the old data will be copied to the new block. For a realloc that reduces the size of the block, the old data will be truncated. … 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
In C: #include <string.h> // memcpy #include <stdlib.h> //realloc In C++, remove the .h and prefix with a c. In C++, they will be placed in the std namespace, but are also global.
Is there any danger in allocating memory with realloc using the initially NULL-valued ptr None 7.22.3.5 If ptr is a null pointer, the realloc function behaves like the malloc function for the specified size. For the second part: int* ptr; // no value given to ptr would it be a problem to call realloc using … Read more