BUG: C4306 Warning when Using Signal Handler

Q119224

7.00 | 1.00 1.50 MS-DOS | WINDOWS kbtool kbbuglist ---------------------------------------------------------------------- The information in this article applies to: - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++ for Windows, versions 1.0 and 1.5 ---------------------------------------------------------------------- SYMPTOMS ======== When using the signal function in the medium-, large-, or huge-memory models of C/C++ version 7.0, 8.0, or 8.0c, it is possible to get the following warning message when warning level 4 (/W4) is used: In C/C++ versions 8.0 and 8.0c, the warning appears as: warning C4306: 'cast' : conversion from 'const int ' to 'void (__far __cdecl *)(int )' of greater size In C/C++ version 7.0, the warning appears as: warning C4306: conversion of integral type to pointer of greater size This is a minor warning and can safely be ignored. CAUSE ===== This warning occurs because of incorrect definitions of SIG_DFL, SIG_IGN, and SIG_ERR in the SIGNAL.H header file. These definitions are function pointers that are being assigned integer values. Far function calls require four bytes rather than the two bytes that an integer uses. RESOLUTION ========== This warning message can be fixed by changing the definitions of SIG_DFL, SIG_IGN, and SIG_ERR in the SIGNAL.H file as follows: /* if small or compact model */ #if ((defined (_M_I86SM)) || (defined (_M_I86CM))) #define SIG_DFL (void (__cdecl *)(int))0 #define SIG_IGN (void (__cdecl *)(int))1 #define SIG_ERR (void (__cdecl *)(int))-1 /* other models */ #else #define SIG_DFL (void (__cdecl *)(int))0L #define SIG_IGN (void (__cdecl *)(int))1L #define SIG_ERR (void (__cdecl *)(int))-1L #endif Instead of changing the SIGNAL.H file, however, you can use a pragma to disable the warning as follows: #pragma warning (disable:4306) MORE INFORMATION ================ This problem can be reproduced using the SIGNAL.C sample that is available in the "Run-Time Library Reference" or in the online Help for C/C++ version 7.0 or Visual C/C++ versions 1.0 and 1.5. Additional reference words: 7.00 1.00 1.50 KBCategory: kbtool kbbuglist KBSubcategory: CLIss

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Technology : kbVCsearch kbAudDeveloper kbPTProdChange kbvc150 kbvc100 kbZNotKeyword3 kbCVC700DOS


Last Reviewed: May 6, 2001
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