Q119331: INFO: Compiler Errors with Win32 APIs Ending in "A" or "W"

Article: Q119331
Product(s): Microsoft C Compiler
Version(s): 1.0,2.0,2.1,2.2,4.0,4.1,5.0,6.0
Operating System(s): 
Keyword(s): kberrmsg kbCompiler kbVC100 kbVC200 kbVC210 kbVC220 kbVC400 kbVC410 kbVC500 kbVC600
Last Modified: 24-JUN-2002

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 2.2, 4.0, 4.1, 5.0, 6.0 
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SUMMARY
=======

When the names of Win32 APIs appear in compiler error messages, they may have
either an "A" or a "W" appended to the API name. For example, the API
CreateProcess() can appear as "CreateProcessA" in an error message such as the
following:

  error C2664: 'CreateProcessA' : cannot convert parameter 9

The reason for this is that many Win32 APIs have both a ANSI ("A") and a Unicode
("W") version. The Windows NT header files use macros such as the following to
select the appropriate API:

  #ifdef UNICODE
  #define CreateProcess  CreateProcessW
  #else
  #define CreateProcess  CreateProcessA
  #endif // !UNICODE

MORE INFORMATION
================

The Windows NT header files also contain more complicated macros, which use
hidden arguments:

     #define CreateWindowA(lpClassName, lpWindowName, dwStyle, x, y,\ 
     nWidth, nHeight, hWndParent, hMenu, hInstance, lpParam)\ 
     CreateWindowExA(0L, lpClassName, lpWindowName, dwStyle, x, y,\ 
     nWidth, nHeight, hWndParent, hMenu, hInstance, lpParam)
     #define CreateWindowW(lpClassName, lpWindowName, dwStyle, x, y,\ 
     nWidth, nHeight, hWndParent, hMenu, hInstance, lpParam)\ 
     CreateWindowExW(0L, lpClassName, lpWindowName, dwStyle, x, y,\ 
     nWidth, nHeight, hWndParent, hMenu, hInstance, lpParam)
     #ifdef UNICODE
     #define CreateWindow  CreateWindowW
     #else
     #define CreateWindow  CreateWindowA
     #endif // !UNICODE

In this case, an error message may refer to argument 8 on a line of your code,
but the argument is really argument 7 in your source code.

Other error messages that may have unexpected diagnostic information because of
macro expansion include the following:

- C1056: compiler limit : out of macro expansion space

- C2014: preprocessor command must start as first nonwhite space

- C2055: expected formal parameter list, not a type list

- C2095: 'function' : actual parameter has type void : parameter 'number'

- C2172: 'function' : actual parameter is not a pointer : parameter 'number'

- C2173: 'function' : actual parameter is not a pointer : parameter 'number1',
  parameter list 'number2'

- C2174: 'function' : actual parameter has type 'void' : parameter 'number1',
  parameter list 'number2'

- C2660: 'function' : function does not take 'number' parameters

- C2664: 'function' : cannot convert parameter 'number' from 'type1' to 'type2'

- C4022: 'function' : pointer mismatch for actual parameter 'number'

- C4024: 'function' : different types for formal and actual parameter 'number'

Additional query words: 8.00 9.00 9.10 10.00 10.10

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Keywords          : kberrmsg kbCompiler kbVC100 kbVC200 kbVC210 kbVC220 kbVC400 kbVC410 kbVC500 kbVC600 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbvc100 kbVC220 kbVC410 kbVC500 kbVC600 kbVC200 kbVC210 kbVC32bitSearch kbVC500Search
Version           : :1.0,2.0,2.1,2.2,4.0,4.1,5.0,6.0
Issue type        : kbinfo

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