__ud2
The latest version of this topic can be found at __ud2.
Microsoft Specific**
Generates an undefined instruction.
Syntax
void __ud2();
Remarks
The processor raises an invalid opcode exception if you execute an undefined instruction.
The __ud2 function is equivalent to the UD2 machine instruction, and is available only in kernel mode. For more information, search for the document, "Intel Architecture Software Developer's Manual, Volume 2: Instruction Set Reference," at the Intel Corporation site.
Requirements
| Intrinsic | Architecture |
|---|---|
__ud2 |
x86, x64 |
Header file <intrin.h>
END Microsoft Specific
Example
The following example executes an undefined instruction, which raises an exception. The exception handler then changes the return code from zero to one.
// __ud2_intrinsic.cpp
#include <stdio.h>
#include <intrin.h>
#include <excpt.h>
// compile with /EHa
int main() {
// Initialize the return code to 0.
int ret = 0;
// Attempt to execute an undefined instruction.
printf("Before __ud2(). Return code = %d.\n", ret);
__try {
__ud2();
}
// Catch any exceptions and set the return code to 1.
__except(EXCEPTION_EXECUTE_HANDLER){
printf(" In the exception handler.\n");
ret = 1;
}
// Report the value of the return code.
printf("After __ud2(). Return code = %d.\n", ret);
return ret;
}
Before __ud2(). Return code = 0.
In the exception handler.
After __ud2(). Return code = 1.