INFO: Visual C++ 5.0 Readme, Language Issues

ID: Q165684

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions, version 5.0

SUMMARY

Language Issues

Member Templates Not Supported by the Compiler Addendums to the __declspec Documentation Behavior of In-Constructor Exception Handling Not Correctly Documented Size Mismatch for Type bool in Visual C++ 4.2 Programs Built with Visual C++ 5.0

MORE INFORMATION

Member Templates Not Supported by the Compiler

Simple member templates may not generate a compiler error. Use of member templates can result in undefined behavior.

Addendums to the __declspec Documentation

The documentation for the _declspec keyword is missing the following information:

Addendum One

The __declspec keywords should be placed at the beginning of a simple declaration. __declspec keywords placed after * or & and in front of the variable identifier in a declaration will be ignored by the compiler without error message or warnings. See the __declspec topic in Language Quick Reference for more information about using the __declspec attributes.

Addendum Two

The following three declarations are equivalent:

#define WINAPI __declspec(nothrow) __stdcall

void WINAPI foo1();

void __declspec(nothrow) __stdcall foo2();

void __stdcall foo3() throw();

Using "void __declspec(nothrow) __stdcall foo2();" has the advantage that you can use an API definition, such as the illustrated by the #define statement, to easily specify nothrow on a set of functions. The third declaration, "void __stdcall foo3() throw();" is the syntax defined by the C++ standard.

Behavior of In-Constructor Exception Handling Not Correctly Documented

If you use the operator new without any extra arguments, and compile with the /GX, /EHs, or /EHa option, the compiler will generate code to call operator delete if the constructor throws an exception.

If you use the placement new form of the new operator, the form with arguments in addition to the size of the allocation, the compiler does not support a placement form of the delete operator if the constructor throws an exception.

Example


   class A {

   public:
       A(int) { throw "Fail!"; }
   };

   void foo(void)
   {
       try {
           // heap memory pointed to by pa1 will be deallocated
           // by calling ::operator delete(void*).

           A* pa1 = new A(10);

       } catch (...) {
       }

       try {
           // This will call ::operator new(size_t, char*, int).
           // When A::A(int) does a throw, we should call
           // ::operator delete(void*, char*, int) to deallocate
           // the memory pointed to by pa2, but that's something
           // we don't support yet, so we'll leak memory.

           A* pa2 = new(__FILE__, __LINE__) A(20);

       } catch (...) {
       }
   }

Size Mismatch for Type bool in Visual C++ 4.2 Programs Built with Visual C++ 5.0

In Visual C++4.2, the Standard C++ header files contained a typedef that equated bool with int. In Visual C++ 5.0, bool is implemented as a built-in type with a size of 1 byte. That means that for Visual C++ 4.2, a call of sizeof(bool) yields 4, while in Visual C++ 5.0, the same call yields 1. This can cause memory corruption problems if you have defined structure members of type bool in Visual C++ 4.2 and are mixing object files (OBJ) and/or DLLs built with the 4.2 and 5.0 compilers.

Keywords :
Version : 5.0
Platform : NT WINDOWS
Issue type :