diff options
Diffstat (limited to 'jmorecfg.h')
| -rw-r--r-- | jmorecfg.h | 29 |
1 files changed, 26 insertions, 3 deletions
@@ -6,7 +6,8 @@ * Modified 1997-2009 by Guido Vollbeding. * libjpeg-turbo Modifications: * Copyright (C) 2009, 2011, 2014-2015, D. R. Commander. - * For conditions of distribution and use, see the accompanying README file. + * For conditions of distribution and use, see the accompanying README.ijg + * file. * * This file contains additional configuration options that customize the * JPEG software for special applications or support machine-dependent @@ -146,13 +147,35 @@ typedef unsigned int UINT16; typedef short INT16; #endif -/* INT32 must hold at least signed 32-bit values. */ +/* INT32 must hold at least signed 32-bit values. + * + * NOTE: The INT32 typedef dates back to libjpeg v5 (1994.) Integers were + * sometimes 16-bit back then (MS-DOS), which is why INT32 is typedef'd to + * long. It also wasn't common (or at least as common) in 1994 for INT32 to be + * defined by platform headers. Since then, however, INT32 is defined in + * several other common places: + * + * Xmd.h (X11 header) typedefs INT32 to int on 64-bit platforms and long on + * 32-bit platforms (i.e always a 32-bit signed type.) + * + * basetsd.h (Win32 header) typedefs INT32 to int (always a 32-bit signed type + * on modern platforms.) + * + * qglobal.h (Qt header) typedefs INT32 to int (always a 32-bit signed type on + * modern platforms.) + * + * This is a recipe for conflict, since "long" and "int" aren't always + * compatible types. Since the definition of INT32 has technically been part + * of the libjpeg API for more than 20 years, we can't remove it, but we do not + * use it internally any longer. We instead define a separate type (JLONG) + * for internal use, which ensures that internal behavior will always be the + * same regardless of any external headers that may be included. + */ #ifndef XMD_H /* X11/xmd.h correctly defines INT32 */ #ifndef _BASETSD_H_ /* Microsoft defines it in basetsd.h */ #ifndef _BASETSD_H /* MinGW is slightly different */ #ifndef QGLOBAL_H /* Qt defines it in qglobal.h */ -#define __INT32_IS_ACTUALLY_LONG typedef long INT32; #endif #endif |