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

ID: Q119331

The information in this article applies to:

The Microsoft C/C++ Compiler (CL.EXE)
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 2.2, 4.0, 4.1, 5.0, 6.0

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

Keywords : kberrmsg kbCompiler kbVC100 kbVC200 kbVC210 kbVC220 kbVC400 kbVC410 kbVC500 kbVC600
Version : WINNT:1.0,2.0,2.1,2.2,4.0,4.1,5.0;
Platform : NT WINDOWS
Issue type : kbprb