Article ID: 111753
Article Last Modified on 10/2/2003
APPLIES TO
- The C Run-Time (CRT)
This article was previously published under Q111753
SUMMARY
The documentation in the Microsoft C "Run-Time Library Reference" for the assert macro states that in Windows an assertion failure causes a pop-up box to be displayed. This is stated similarly in the online help. Although this is true for 16-bit Windows applications, under Win32 the macro just causes the application to abort; no pop-up window is displayed.
The Visual C++ 2.0 documentation has the correct information.
MORE INFORMATION
The C run-time assert() macro was originally designed to display its diagnostic message using console output. In the 16-bit Windows version of the C run time, the macro was modified to use the Windows Graphical User Interface (GUI) application programming interface (API). This was necessary because 16-bit Windows does not support a console API.
Unlike 16-bit Windows, however, Win32 has both a GUI and console API set, and therefore the assert() macro returns to its original form as a console output macro.
It is possible to create a user-defined version of the assert() macro that displays its diagnostic message in a pop-up window. The sample code provided below shows one way of doing this:
Sample Code
/* Compile options needed: none
*/
#include <windows.h>
#include <stdio.h>
#include <process.h>
// Prototype for the function called by the assert macro.
void ShowAssertion(void * expr, void * filename, unsigned lineno);
// The following should all be on one line. It wraps around because
// of its length.
#define assert(exp) (void)( (exp) || (ShowAssertion(#exp, __FILE__,
__LINE__), 0) )
static char AssertString[] = "Expression %s, File %s, Line %d\n";
void ShowAssertion(void * expr, void * filename, unsigned lineno)
{
char buffer[256];
sprintf( buffer, AssertString, expr, filename, lineno );
MessageBox( NULL, buffer, "ASSERTION FAILED",
MB_OK | MB_ICONHAND | MB_TASKMODAL );
abort();
}
Additional query words: 2.00 debug runtime run time
Keywords: kbcrt kbdocfix kbdocerr KB111753
