source: vbox/trunk/include/iprt/assertcompile.h

/** @file
 * IPRT - Compile Time Assertions.
 */

/*
 * Copyright (C) 2006-2023 Oracle and/or its affiliates.
 *
 * This file is part of VirtualBox base platform packages, as
 * available from https://www.virtualbox.org.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, in version 3 of the
 * License.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <https://www.gnu.org/licenses>.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
 * in the VirtualBox distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 *
 * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
 */

#ifndef IPRT_INCLUDED_assertcompile_h
#define IPRT_INCLUDED_assertcompile_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif

#include <iprt/cdefs.h>

/** @defgroup  grp_rt_assert_compile    Compile time assertions
 * @ingroup grp_rt
 *
 * These assertions are used to check structure sizes, member/size alignments
 * and similar compile time expressions.
 *
 * @remarks As you might have noticed, the AssertCompile macros don't follow the
 *          coding guidelines wrt to macros supposedly being all uppercase and
 *          underscored.  For various reasons they don't, and nobody has
 *          complained yet.
 *
 * @{
 */


/**
 * RTASSERTTYPE is the type the AssertCompile() macro redefines.
 * It has no other function and shouldn't be used.
 * Visual C++ uses this.
 */
#ifndef __ASSEMBLER__
typedef int RTASSERTTYPE[1];
#endif

/**
 * RTASSERTVAR is the type the AssertCompile() macro redefines.
 * It has no other function and shouldn't be used.
 *
 * GCC and IBM VisualAge C/C++ uses this.  GCC doesn't technicaly need this
 * global scope one as it declares it for each use, however things get
 * complicated in C++ code where most GCC and clang versions gets upset by mixed
 * "C" and "C++" versions of the symbol when using inside and outside
 * RT_C_DECLS_BEGIN/END.  The GCC 3.3.x and 3.4.x versions we use, OTOH will
 * always complain about unused RTASSERTVAR for each AssertCompileNS use in a
 * function if we declare it globally, so we don't do it for those, but we do
 * for 4.x+ to prevent linkage confusion.
 */
#ifndef __ASSEMBLER__
# if !defined(__cplusplus) || !defined(__GNUC__)
extern int RTASSERTVAR[1];
# elif RT_GNUC_PREREQ(4, 0) || defined(__clang_major__) /* Not sure when they fixed the global scoping __unused__/whatever problem. */
RT_C_DECLS_BEGIN
extern int RTASSERTVAR[1];
RT_C_DECLS_END
# endif
#endif

/** @def RTASSERT_HAVE_STATIC_ASSERT
 * Indicates that the compiler implements static_assert(expr, msg).
 */
#ifndef __ASSEMBLER__
# ifdef _MSC_VER
#  if _MSC_VER >= 1600 && defined(__cplusplus) && !defined(VBOX_WITH_PARFAIT)
#  define RTASSERT_HAVE_STATIC_ASSERT
#  endif
# endif
# if defined(__GNUC__) && defined(__GXX_EXPERIMENTAL_CXX0X__)
#  define RTASSERT_HAVE_STATIC_ASSERT
# endif
# if RT_CLANG_PREREQ(6, 0)
#  if __has_feature(cxx_static_assert) || __has_feature(c_static_assert)
#   define RTASSERT_HAVE_STATIC_ASSERT
#  endif
# endif
#endif
#ifdef DOXYGEN_RUNNING
# define RTASSERT_HAVE_STATIC_ASSERT
#endif

/** @def AssertCompileNS
 * Asserts that a compile-time expression is true. If it's not break the build.
 *
 * This differs from AssertCompile in that it accepts some more expressions
 * than what C++0x allows - NS = Non-standard.
 *
 * @param   expr    Expression which should be true.
 */
#ifdef __ASSEMBLER__
# define AssertCompileNS(expr)
#elif defined(__GNUC__)
# define AssertCompileNS(expr)  AssertCompileNS2(expr,RTASSERTVAR)
# define AssertCompileNS2(expr,a_VarName)   extern int a_VarName[         1    ] __attribute__((__unused__)), \
                                                       a_VarName[(expr) ? 1 : 0] __attribute__((__unused__))
#elif defined(__IBMC__) || defined(__IBMCPP__)
# define AssertCompileNS(expr)  extern int RTASSERTVAR[(expr) ? 1 : 0]
#else
# define AssertCompileNS(expr)  typedef int RTASSERTTYPE[(expr) ? 1 : 0]
#endif

/** @def AssertCompile
 * Asserts that a C++0x compile-time expression is true. If it's not break the
 * build.
 * @param   expr    Expression which should be true.
 */
#ifdef RTASSERT_HAVE_STATIC_ASSERT
# ifdef __cplusplus
#  define AssertCompile(expr)    static_assert(!!(expr), #expr)
# else
#  define AssertCompile(expr)    _Static_assert(!!(expr), #expr)
# endif
#else
# define AssertCompile(expr)    AssertCompileNS(expr)
#endif

/** @def RTASSERT_OFFSET_OF()
 * A offsetof() macro suitable for compile time assertions.
 * Both GCC v4 and VisualAge for C++ v3.08 has trouble using RT_OFFSETOF.
 */
#if defined(__GNUC__)
# if __GNUC__ >= 4
#  define RTASSERT_OFFSET_OF(a_Type, a_Member)  __builtin_offsetof(a_Type, a_Member)
# else
#  define RTASSERT_OFFSET_OF(a_Type, a_Member)  RT_OFFSETOF(a_Type, a_Member)
# endif
#elif (defined(__IBMC__) || defined(__IBMCPP__)) && defined(RT_OS_OS2)
# define RTASSERT_OFFSET_OF(a_Type, a_Member)   __offsetof(a_Type, a_Member)
#elif (defined(__WATCOMC__) && defined(__cplusplus))
# define RTASSERT_OFFSET_OF(a_Type, a_Member)   __offsetof(a_Type, a_Member)
#else
# define RTASSERT_OFFSET_OF(a_Type, a_Member)   RT_OFFSETOF(a_Type, a_Member)
#endif


/** @def AssertCompileSize
 * Asserts a size at compile.
 * @param   type    The type.
 * @param   size    The expected type size.
 */
#define AssertCompileSize(type, size) \
    AssertCompile(sizeof(type) == (size))

/** @def AssertCompileSizeAlignment
 * Asserts a size alignment at compile.
 * @param   type    The type.
 * @param   align   The size alignment to assert.
 */
#define AssertCompileSizeAlignment(type, align) \
    AssertCompile(!(sizeof(type) & ((align) - 1)))

/** @def AssertCompileMemberSize
 * Asserts a member offset alignment at compile.
 * @param   type    The type.
 * @param   member  The member.
 * @param   size    The member size to assert.
 */
#define AssertCompileMemberSize(type, member, size) \
    AssertCompile(RT_SIZEOFMEMB(type, member) == (size))

/** @def AssertCompileMemberSizeAlignment
 * Asserts a member size alignment at compile.
 * @param   type    The type.
 * @param   member  The member.
 * @param   align   The member size alignment to assert.
 */
#define AssertCompileMemberSizeAlignment(type, member, align) \
    AssertCompile(!(RT_SIZEOFMEMB(type, member) & ((align) - 1)))

/** @def AssertCompileMemberAlignment
 * Asserts a member offset alignment at compile.
 * @param   type    The type.
 * @param   member  The member.
 * @param   align   The member offset alignment to assert.
 */
#define AssertCompileMemberAlignment(type, member, align) \
    AssertCompile(!(RTASSERT_OFFSET_OF(type, member) & ((align) - 1)))

/** @def AssertCompileMemberOffset
 * Asserts an offset of a structure member at compile.
 * @param   type    The type.
 * @param   member  The member.
 * @param   off     The expected offset.
 */
#define AssertCompileMemberOffset(type, member, off) \
    AssertCompile(RTASSERT_OFFSET_OF(type, member) == (off))

/** @def AssertCompile2MemberOffsets
 * Asserts that two (sub-structure) members in union have the same offset.
 * @param   type    The type.
 * @param   member1 The first member.
 * @param   member2 The second member.
 */
#define AssertCompile2MemberOffsets(type, member1, member2) \
    AssertCompile(RTASSERT_OFFSET_OF(type, member1) == RTASSERT_OFFSET_OF(type, member2))

/** @def AssertCompileAdjacentMembers
 * Asserts that two structure members are adjacent.
 * @param   type    The type.
 * @param   member1 The first member.
 * @param   member2 The second member.
 */
#define AssertCompileAdjacentMembers(type, member1, member2) \
    AssertCompile(RTASSERT_OFFSET_OF(type, member1) + RT_SIZEOFMEMB(type, member1) == RTASSERT_OFFSET_OF(type, member2))

/** @def AssertCompileMembersAtSameOffset
 * Asserts that members of two different structures are at the same offset.
 * @param   type1   The first type.
 * @param   member1 The first member.
 * @param   type2   The second type.
 * @param   member2 The second member.
 */
#define AssertCompileMembersAtSameOffset(type1, member1, type2, member2) \
    AssertCompile(RTASSERT_OFFSET_OF(type1, member1) == RTASSERT_OFFSET_OF(type2, member2))

/** @def AssertCompileMembersSameSize
 * Asserts that members of two different structures have the same size.
 * @param   type1   The first type.
 * @param   member1 The first member.
 * @param   type2   The second type.
 * @param   member2 The second member.
 */
#define AssertCompileMembersSameSize(type1, member1, type2, member2) \
    AssertCompile(RT_SIZEOFMEMB(type1, member1) == RT_SIZEOFMEMB(type2, member2))

/** @def AssertCompileMembersSameSizeAndOffset
 * Asserts that members of two different structures have the same size and are
 * at the same offset.
 * @param   type1   The first type.
 * @param   member1 The first member.
 * @param   type2   The second type.
 * @param   member2 The second member.
 */
#define AssertCompileMembersSameSizeAndOffset(type1, member1, type2, member2) \
    AssertCompile(   RTASSERT_OFFSET_OF(type1, member1) == RTASSERT_OFFSET_OF(type2, member2) \
                  && RT_SIZEOFMEMB(type1, member1) == RT_SIZEOFMEMB(type2, member2))

/** @} */

#endif /* !IPRT_INCLUDED_assertcompile_h */