new and reallocating memory [duplicate]

Question

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How do you 'realloc' in C++? (4 answers)

Closed 8 years ago.

new[] doesn't support change the size of allocated memory, does it?

For example, I allocated memory with new[] for buffer (array of char) and I want to get the additional memory.

Should I use malloc/realloc instead in this case?

Answer 1

new does not support that.

You can mimic the behavior of realloc manually using new, delete and memcpy.

By the way, you should always use the same family of methods i.e. either malloc / realloc / free or new / delete, and not mix realloc with new / delete. See for example the FMM errors reported by Purify.

Answer 2

The closest you can come in standard C++ without resorting to the C holdovers malloc and realloc is to use std::vector<char>. This can be resized at any time, and if the underlying storage gets reallocated the contents will be automatically copied.

Answer 3

Use std::vector. You'll not have to deal with these issues.

Answer 4

It is not a good idea to use malloc/realloc with new.

new will not support reallocating more memory once applied.

So a good idea would be to create a new buffer with extra memory, memcpy and delete the old buffer. Then point to this new buffer.

Answer 5

You should use std::vector instead. It can be resized.