Heap memory allocation crash with std::wstring

Question

I have a big problem with std::wstring memory allocation. The program crash when I try to use this code:

size_t size;
mbstowcs_s(&size, NULL, 0, buffer, _TRUNCATE);
wchar_t *buffer2 = (wchar_t*)malloc(size + 1);
mbstowcs_s(&size, buffer, buffer_size, buffer, _TRUNCATE);
buffer2[size] = '\0';

std::wstring data(buffer);

the crash is on the last line and doesn't happen if I use the following line:

std::wstring data(L"hello");

the error is memory heap allocation failure and the result is the crash of the program. Why? What's wrong?

Answer 1

wchar_t *buffer2 = (wchar_t*)malloc((size + 1) * sizeof(wchar_t));
                                               ^^^^^^^^^^^^^^^^^

malloc allocates a number of bytes - you wan't a number of wchar_t 's

If you're using c++, the correct way is:

wchar_t *buffer2 = new wchar_t[size+1];

Answer 2

如果您使用std :: wstring我假设您使用的是C ++，请不要使用malloc，请使用new＆delete（只是一个注释）

Answer 3

std::vector seems to be a good way to make a buffer here. Its constructor receives elements number (not bytes) and you don't have to remember to delete the memory.