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# FIX: C1001 Error Compiling Naked Function with /Og and /G5

Article ID: 122302

Article Last Modified on 7/5/2005

APPLIES TO

- Microsoft Visual C++ 2.0 Professional Edition

This article was previously published under Q122302

## SYMPTOMS

Compiling a function with the __declspec(naked) modifier, but without an __asm block for the epilog code, and using the /Og and /G5 switches, results in the following error:
fatal error C1001: INTERNAL COMPILER ERROR
(compiler file 'l:\b_bld\c2\P2\main.c', line 374)
Please choose the Technical Support command on the Visual C++ Help menu, or open the Technical Support help file for more information

## RESOLUTION

Implement a epilog code block in your function.

## STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was fixed in Microsoft Visual C++, 32-bit Edition, version 4.0.

## MORE INFORMATION

If a function is declared with the __declspec(naked) modifier, the compiler will not generate any prolog or epilog code. Users should implement their own prolog and epilog code, using blocks of inline assembler code.
NOTE: without proper prolog and epilog code, the code will not execute correctly.

### Sample Code

    /* Compile options needed: /Og /G5
       Note that /O1, /O2, and /Ox all imply /Og
    */

    void __declspec(naked) NakedFunction()
    {
        __asm
        {
        // prolog code
        }

        printf( "Inside naked function\n" );

        // note: epilog __asm block missing
    }

Additional query words: 2.00 9.00 buglist2.00

Keywords: kbbug kbfix KB122302