INFO: Visual C++ 5.0 Readme, Compiler, Linker and Utilities

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

SUMMARY

Compiler, Linker, Debugger, and MIDL Compiler Issues

• Windbg Cannot Use Visual C++ 5.0 Debugging Information.
• _declspec(novtable)
• _ATL_MIN_CRT and Link Error "unresolved external symbol _main"
• DCOM95 Available for Distributed Applications
• /WS:AGGRESSIVE (Aggressively Trim Process Memory)
• /FD (Generate File Dependencies)
• _MSC_EXTENSIONS Compiler Macro
• Option Precedence and the CL Environment Variable
• /Zm (Specify Memory Allocation Limit)
• Compiler Now Documents Type Library Dependencies
• Keywords _emul and _emulu Not Documented
• New Linker Error: Linker Tools Error LNK1189
• Benefit of Using the Linker's /OPT:ICF Option
• Debugging Windows API Functions with NT Symbols Loaded
• If Screen Flashes During Build or the Wrong Code Page Is Used When
• Debugging a Console Application
• Incorrect Documentation for the Clean Menu Command
• MIDL2020: error generating type library: save all changes failed
• Error RC2104 : undefined keyword or key name: MFT_STRING
• Error Command Line Warning MIDL1009:unknown argument ignored
• Additional Information on the C2065 Compiler Error
• Documentation for Error C2712 Incomplete
• Compiler Warning (level 4) C2498
• Compiler Warning (level 4) C4238
• Compiler Warning (level 3) C4800
• Compiler Warning (level 1) C4804
• Compiler Warning (level 1) C4805
• Compiler Warning (level 1) C4806
• Compiler Warning (level 1) C4807
• Compiler Warnings (level 1) C4808
• Compiler Warning (level 1) C4809

MORE INFORMATION

Windbg Cannot Use Visual C++ 5.0 Debugging Information

Because of changes to the format of debugging information in Visual C++ 5.0, you will not be able to use the Windbg debugger (distributed in the NT 4.0 Win32 SDK) to do source level debugging of programs created with Visual C++ 5.0.

_declspec(novtable)

This form of _declspec can be applied to any class declaration, but should only be applied to pure interface classes, i.e. classes that will never be instantiated on their own. The _declspec stops the compiler from generating code to initialize the vfptr in the constructor(s) and destructor of the class. In many cases, this removes the only references to the vtable that are associated with the class and, thus, the linker will remove it. Using this form of _declspec can result in a significant reduction in code size.

_ATL_MIN_CRT and Link Error "unresolved external symbol _main"

When you build a Release version of an ATL project, you can get the following link error:

   LIBCMT.LIB(crt0.obj) : error LNK2001: unresolved external symbol _main

To avoid this error, do one of the following:

• Remove _ATL_MIN_CRT from the list of preprocessor defines to allow CRT startup code to be included. On the Project menu, click Settings. In the Settings For: drop down list, choose Multiple Configurations. In the Select project configuration(s) to modify dialog box that appears, click the check boxes for all Release versions, and then click OK. On the C/C++ tab, choose the General category. Remove _ATL_MIN_CRT from the Preprocessor definitions edit box.
• If possible, remove calls to CRT functions that require CRT startup code. Instead, use their Win32 equivalents. For example, use lstrcmp instead of strcmp. Known functions that require CRT startup code are some of the string and floating point functions.

DCOM95 Available for Distributed Applications

The Microsoft Distributed COM (DCOM) files for Windows 95 are useful for creating distributed applications. Some Visual C++ 5.0 samples require DCOM. You can find DCOM95 in the \dcom95 directory on the disc that includes "Microsoft Visual C++" on the label. (Disc 1 if you purchased Visual C++; Disc 3 if you purchased Visual Studio.) Check out the Visual C++ 5.0 Compiler COM support and Active Template Library ( ATL) with DCOM95.

/WS:AGGRESSIVE (Aggressively Trim Process Memory)

Use this linker option to add the WS_AGGRESSIVE attribute to your application's image. The Windows NT 4.0 loader will recognize this attribute and aggressively trim the working set of the process when it is not active. Using this option is similar to adding the following call throughout your application:

   SetProcessWorkingSetSize(hThisProcess, -1, -1)

If the speed of your application is important, do not use /WS:AGGRESSIVE without testing the resulting performance implications. Ideal candidates are processes that tend to operate in the background, such as services and screen savers.

/FD (Generate File Dependencies)

The development environment's build system uses the /FD option to ensure that the most reliable dependency information is used when it builds your project.

_MSC_EXTENSIONS Compiler Macro

This macro is defined unless you compile with /Za for ANSI compatibility. Its value, when defined, is 1.

Option Precedence and the CL Environment Variable

Compiler options are processed "left to right", and when a conflict is detected, the last (right-most) option wins. The CL environment variable is processed before the command line, so in any conflicts between CL and the command line, the command line takes precedence.

/Zm (Specify Memory Allocation Limit)

The compiler uses a number of discrete heaps, each of which has a finite limit. The total of the size limits for all heaps is about 105 MB, but when any one heap is exhausted, the compiler cannot continue. Memory is allocated only as needed; the 105 MB limit is just to keep from using too much memory. Exceeding any one of the discrete-heap size limits occurs only in rare circumstances involving very large or very complex programs. Should your program exceed one of these limits, use /Zm to scale the total size of all the limits. For example, when /Zm200 is specified, the total of all heap size limits is 210MB.

Compiler Now Documents Type Library Dependencies

The compiler provides the full path to any typelib dependency required by the typelib it is currently processing. The path is written, in the form of comments, into the typelib header (.TLH) that the compiler generates for each processed typelib.

If a typelib includes references to types defined in other typelibs, then the .TLH file will include comments of the following sort:

   //

   // Cross-referenced type libraries:

   //

   //  #import "c:\path\typelib0.tlb"

   //

You must determine which of the dependency comments are not otherwise provided for by system headers and then provide an #import directive at some point before the #import directive of the dependent typelib in order to resolve the errors.

Keywords _emul and _emulu Not Documented

Syntax:

   _int64 _emul(long, long);

   unsigned _int64 _emulu(unsigned long, unsigned long);

New Linker Error: Linker Tools Error LNK1189

   LIBTOOMANYMEMBERS:: library limit of number objects exceeded

Benefit of Using the Linker's /OPT:ICF Option

The /OPT:ICF[,iterations] option removes identical COMDAT records in order to reduce the size of the executable produced by the linker. The iterations value specifies the number of times to repeat the search for identical COMDAT records. If /OPT:REF is specified, /OPT:ICF is on by default unless you specify /OPT:NOICF as well.

Debugging Windows API functions with NT Symbols Loaded

If you have the NT symbols loaded and you want to debug Windows API functions, you need to enter the decorated name of the function while setting a breakpoint on the function. For example, if you want to set breakpoint on the MessageBeep function, use the decorated name _MessageBeep@4. The decorated name can be obtained in the map file created through linker options.

If Screen Flashes During Build or the Wrong Code Page is used When Debugging a Console Application

If you are using Windows 95, delete any of the following files from your computer:

• _DEFAULT.PIF
• DEFAULT.PIF
• CONAGENT.PIF

Incorrect Documentation for the Clean Menu Command

The Clean command is incorrectly documented in the "Remove Intermediate Files" topic as follows:

   You can remove all files from the intermediate directories in any
   project configuration in your project workspace.

MIDL2020: error generating type library: save all changes failed

This error can result if the path to the .IDL file is longer than 126 characters, which is because oleaut32.dll does not currently support path names that are greater than 126 characters. The workaround is to reduce the path to the .IDL file so that it is less than 126 characters.

Error RC2104 : undefined keyword or key name: MFT_STRING

If you encounter this error, open MCL\MFC\Include\AfxRes.h and add the following include directive:

   #include <winresrc.h>

Error Command Line Warning MIDL1009 : unknown argument ignored

MIDL.exe version 3.01.75 generates this error if its arguments are passed in a response file and one of the arguments is an MBCS-character file name that contains a space.

Workarounds:

• Use a batch file to invoke MIDL with its arguments.
• Delete the space from the MBCS file name.

Additional Information on the C2065 Compiler Error

The following information belongs in the tips section of the C2065 compiler error:

Make sure you're using proper namespace scope. For example, in order to properly resolve ANSI C++ Standard Library functions and operators, you must state that you're using the std namespace with the using directive.

For example, unless the using directive is uncommented, the following sample will fail to compile because the cout stream is defined in the std namespace:

   #include <iostream>

   // using namespace std;

   void main()

   {
     cout << "Hello" << endl;
   }

Documentation for Error C2712 Incomplete

The documentation for this error should also contain the following information:

The error can be avoided when using the /GX option by not having local variables or parameters with types that have destructors in a function that uses structured exception handling (SEH). Furthermore, SEH cannot be used in constructors or destructors if using /GX. Code that requires SEH can also be moved to another function in order to avoid the error.

Compiler Warning C2498

   C2498 : "%$S' 'novtable' can only be applied to class declarations"

   void __declspec(novtable) f() {
   }

Compiler Warning (level 4) C4238

   nonstandard extension used : class rvalue used as lvalue

   struct C
   {
     C();
   };

   C * pC = &C(); // yields C4238

Compiler Warning (level 3) C4800

   'type' : forcing value to bool 'true' or 'false' (performance warning)

Compiler Warning (level 1) C4804

   '%$L' : unsafe use of type 'bool' in operation

Compiler Warning (level 1) C4805

   '%$L' : unsafe mix of type 'type' and type 'type' in operation

Compiler Warning (level 1) C4806

   '%$L' : unsafe operation: no value of type 'type' promoted to type
   'type' can equal the given constant

Compiler Warning (level 1) C4807

   '%$L' : unsafe mix of type 'type' and signed bitfield of type 'type'

Compiler Warnings (level 1) C4808

   case '%d' is not a valid value for switch condition of type 'bool'

Compiler Warning (level 1) C4809

   switch statement has redundant 'default' label; all possible 'case'
   labels are given