c++ - Will new return NULL in any case?

Question

I know that according to C++ standard in case the new fails to allocate memory it is supposed to throw std::bad_alloc exception. But I have heard that some compilers such as VC6 (or CRT implementation?) do not adhere to it. Is this true ? I am asking this because checking for NULL after each and every new statement makes code look very ugly.

Answer 1

VC6 was non-compliant by default in this regard. VC6's new returned 0 (or NULL).

Here's Microsoft's KB Article on this issue along with their suggested workaround using a custom new handler:

• Operator new does not throw a bad_alloc exception on failure in Visual C++

If you have old code that was written for VC6 behavior, you can get that same behavior with newer MSVC compilers (something like 7.0 and later) by linking in a object file named nothrownew.obj. There's actually a fairly complicated set of rules in the 7.0 and 7.1 compilers (VS2002 and VS2003) to determine whether they defaulted to non-throwing or throwing new.

It seems that MS cleaned this up in 8.0 (VS2005)—now it always defaults to a throwing new unless you specifically link to nothrownew.obj.

Note that you can specify that you want new to return 0 instead of throwing std::bad_alloc using the std::nothrow parameter:

SomeType *p = new(std::nothrow) SomeType;

This appears to work in VC6, so it could be a way to more or less mechanically fix the code to work the same with all compilers so you don't have to rework existing error handling.