On Sun, Oct 19, 2025 at 10:04 PM Yan-Jie Wang <[email protected]> wrote:
> + str=new(::std::nothrow) char[mbSize];
It seems that ConvertBSTRToString calls `operator new[](size_t)` to
allocate memory rather than calling the nothrow version.
#include <comutil.h>
#include <comdef.h>
#include <string.h>
#include <wchar.h>
#include <stdio.h>
#include <new>
void *operator new[](std::size_t size) {
printf("operator new[](size_t) called, %zx\n", size);
void *ptr = malloc(size);
if (!ptr) throw std::bad_alloc();
return ptr;
}
void* operator new[](std::size_t count, const std::nothrow_t& tag )
{
printf("operator new[](size_t,std::nothrow&) called, %zx\n", count);
void *ptr = malloc(count);
if (!ptr) return nullptr;
return ptr;
}
void operator delete[](void *ptr) {
free(ptr);
}
int main(void) {
try {
constexpr unsigned int len = 0x30000000;
::BSTR b1 = (BSTR) malloc((len + 1) * sizeof(wchar_t));
if (!b1) throw std::bad_alloc();
::wmemset(b1, L'a', len);
b1[len] = 0;
::printf(" b1 = %p\n", b1);
char* s1 = ::_com_util::ConvertBSTRToString(b1);
::printf(" s1 = %p\n", s1);
::printf("strlen(s1) = %zd (expecting %d)\n", ::strlen(s1), len);
delete[] b1;
delete[] s1;
} catch (::_com_error& e) {
::printf("com error = %s, code = 0x%lx\n",
e.ErrorMessage(), e.Error());
} catch(::std::exception& e) {
::printf("exception = %s\n", e.what());
}
}
This is the result:
C:\msys64\home\yanjie>cl /nologo Test3.cpp /EHs /link comsuppw.lib
Test3.cpp
C:\msys64\home\yanjie>Test3.exe
b1 = 0104E020
operator new[](size_t) called, 30000001
com error = Not enough memory resources are available to complete
this operation., code = 0x8007000e
C:\msys64\home\yanjie>
We may need to handle the exception in `ConvertBSTRToString` if we
would like to match the behavior of comsuppw.lib.
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