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gecko-dev/mfbt/Assertions.h

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sw=4 et tw=99 ft=cpp:
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at:
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Code.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Jeff Walden <jwalden+code@mit.edu>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/* Implementations of runtime and static assertion macros for C and C++. */
#ifndef mozilla_Assertions_h_
#define mozilla_Assertions_h_
#include "mozilla/Attributes.h"
#include "mozilla/Types.h"
/*
* MOZ_STATIC_ASSERT may be used to assert a condition *at compile time*. This
* can be useful when you make certain assumptions about what must hold for
* optimal, or even correct, behavior. For example, you might assert that the
* size of a struct is a multiple of the target architecture's word size:
*
* struct S { ... };
* MOZ_STATIC_ASSERT(sizeof(S) % sizeof(size_t) == 0,
* "S should be a multiple of word size for efficiency");
*
* This macro can be used in any location where both an extern declaration and a
* typedef could be used.
*
* Be aware of the gcc 4.2 concerns noted further down when writing patches that
* use this macro, particularly if a patch only bounces on OS X.
*/
#ifdef __cplusplus
# if defined(__clang__)
# ifndef __has_extension
# define __has_extension __has_feature /* compatibility, for older versions of clang */
# endif
# if __has_extension(cxx_static_assert)
# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason)
# endif
# elif defined(__GNUC__)
# if (defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason)
# endif
# elif defined(_MSC_VER)
# if _MSC_VER >= 1600 /* MSVC 10 */
# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason)
# endif
# elif defined(__HP_aCC)
# if __HP_aCC >= 62500 && defined(_HP_CXX0x_SOURCE)
# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason)
# endif
# endif
#endif
#ifndef MOZ_STATIC_ASSERT
# define MOZ_STATIC_ASSERT_GLUE1(x, y) x##y
# define MOZ_STATIC_ASSERT_GLUE(x, y) MOZ_STATIC_ASSERT_GLUE1(x, y)
# if defined(__SUNPRO_CC)
/*
* The Sun Studio C++ compiler is buggy when declaring, inside a function,
* another extern'd function with an array argument whose length contains a
* sizeof, triggering the error message "sizeof expression not accepted as
* size of array parameter". This bug (6688515, not public yet) would hit
* defining moz_static_assert as a function, so we always define an extern
* array for Sun Studio.
*
* We include the line number in the symbol name in a best-effort attempt
* to avoid conflicts (see below).
*/
# define MOZ_STATIC_ASSERT(cond, reason) \
extern char MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)[(cond) ? 1 : -1]
# elif defined(__COUNTER__)
/*
* If there was no preferred alternative, use a compiler-agnostic version.
*
* Note that the non-__COUNTER__ version has a bug in C++: it can't be used
* in both |extern "C"| and normal C++ in the same translation unit. (Alas
* |extern "C"| isn't allowed in a function.) The only affected compiler
* we really care about is gcc 4.2. For that compiler and others like it,
* we include the line number in the function name to do the best we can to
* avoid conflicts. These should be rare: a conflict would require use of
* MOZ_STATIC_ASSERT on the same line in separate files in the same
* translation unit, *and* the uses would have to be in code with
* different linkage, *and* the first observed use must be in C++-linkage
* code.
*/
# define MOZ_STATIC_ASSERT(cond, reason) \
typedef int MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __COUNTER__)[(cond) ? 1 : -1]
# else
# define MOZ_STATIC_ASSERT(cond, reason) \
extern void MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)(int arg[(cond) ? 1 : -1])
# endif
#endif
#define MOZ_STATIC_ASSERT_IF(cond, expr, reason) MOZ_STATIC_ASSERT(!(cond) || (expr), reason)
#ifdef __cplusplus
extern "C" {
#endif
extern MFBT_API(void)
MOZ_Crash(void);
extern MFBT_API(void)
MOZ_Assert(const char* s, const char* file, int ln);
#ifdef __cplusplus
} /* extern "C" */
#endif
/*
* MOZ_ASSERT(expr [, explanation-string]) asserts that |expr| must be truthy in
* debug builds. If it is, execution continues. Otherwise, an error message
* including the expression and the explanation-string (if provided) is printed,
* an attempt is made to invoke any existing debugger, and execution halts.
* MOZ_ASSERT is fatal: no recovery is possible. Do not assert a condition
* which can correctly be falsy.
*
* The optional explanation-string, if provided, must be a string literal
* explaining the assertion. It is intended for use with assertions whose
* correctness or rationale is non-obvious, and for assertions where the "real"
* condition being tested is best described prosaically. Don't provide an
* explanation if it's not actually helpful.
*
* // No explanation needed: pointer arguments often must not be NULL.
* MOZ_ASSERT(arg);
*
* // An explanation can be helpful to explain exactly how we know an
* // assertion is valid.
* MOZ_ASSERT(state == WAITING_FOR_RESPONSE,
* "given that <thingA> and <thingB>, we must have...");
*
* // Or it might disambiguate multiple identical (save for their location)
* // assertions of the same expression.
* MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
* "we already set [[PrimitiveThis]] for this Boolean object");
* MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
* "we already set [[PrimitiveThis]] for this String object");
*
* MOZ_ASSERT has no effect in non-debug builds. It is designed to catch bugs
* *only* during debugging, not "in the field".
*/
#ifdef DEBUG
/* First the single-argument form. */
# define MOZ_ASSERT_HELPER1(expr) \
((expr) ? ((void)0) : MOZ_Assert(#expr, __FILE__, __LINE__))
/* Now the two-argument form. */
# define MOZ_ASSERT_HELPER2(expr, explain) \
((expr) ? ((void)0) : MOZ_Assert(#expr " (" explain ")", __FILE__, __LINE__))
/* And now, helper macrology up the wazoo. */
/*
* Count the number of arguments passed to MOZ_ASSERT, very carefully
* tiptoeing around an MSVC bug where it improperly expands __VA_ARGS__ as a
* single token in argument lists. See these URLs for details:
*
* http://connect.microsoft.com/VisualStudio/feedback/details/380090/variadic-macro-replacement
* http://cplusplus.co.il/2010/07/17/variadic-macro-to-count-number-of-arguments/#comment-644
*/
# define MOZ_COUNT_ASSERT_ARGS_IMPL2(_1, _2, count, ...) \
count
# define MOZ_COUNT_ASSERT_ARGS_IMPL(args) \
MOZ_COUNT_ASSERT_ARGS_IMPL2 args
# define MOZ_COUNT_ASSERT_ARGS(...) \
MOZ_COUNT_ASSERT_ARGS_IMPL((__VA_ARGS__, 2, 1, 0))
/* Pick the right helper macro to invoke. */
# define MOZ_ASSERT_CHOOSE_HELPER2(count) MOZ_ASSERT_HELPER##count
# define MOZ_ASSERT_CHOOSE_HELPER1(count) MOZ_ASSERT_CHOOSE_HELPER2(count)
# define MOZ_ASSERT_CHOOSE_HELPER(count) MOZ_ASSERT_CHOOSE_HELPER1(count)
/* The actual macro. */
# define MOZ_ASSERT_GLUE(x, y) x y
# define MOZ_ASSERT(...) \
MOZ_ASSERT_GLUE(MOZ_ASSERT_CHOOSE_HELPER(MOZ_COUNT_ASSERT_ARGS(__VA_ARGS__)), \
(__VA_ARGS__))
#else
# define MOZ_ASSERT(...) ((void)0)
#endif /* DEBUG */
/*
* MOZ_ASSERT_IF(cond1, cond2) is equivalent to MOZ_ASSERT(cond2) if cond1 is
* true.
*
* MOZ_ASSERT_IF(isPrime(num), num == 2 || isOdd(num));
*
* As with MOZ_ASSERT, MOZ_ASSERT_IF has effect only in debug builds. It is
* designed to catch bugs during debugging, not "in the field".
*/
#ifdef DEBUG
# define MOZ_ASSERT_IF(cond, expr) ((cond) ? MOZ_ASSERT(expr) : ((void)0))
#else
# define MOZ_ASSERT_IF(cond, expr) ((void)0)
#endif
/* MOZ_NOT_REACHED_MARKER() expands (in compilers which support it) to an
* expression which states that it is undefined behavior for the compiler to
* reach this point. Most code should probably use the higher level
* MOZ_NOT_REACHED (which expands to this when appropriate).
*/
#if defined(__clang__)
# define MOZ_NOT_REACHED_MARKER() __builtin_unreachable()
#elif defined(__GNUC__)
# if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
# define MOZ_NOT_REACHED_MARKER() __builtin_unreachable()
# endif
#elif defined(_MSC_VER)
# define MOZ_NOT_REACHED_MARKER() __assume(0)
#endif
/*
* MOZ_NOT_REACHED(reason) indicates that the given point can't be reached
* during execution: simply reaching that point in execution is a bug. It takes
* as an argument an error message indicating the reason why that point should
* not have been reachable.
*
* // ...in a language parser...
* void handle(BooleanLiteralNode node)
* {
* if (node.isTrue())
* handleTrueLiteral();
* else if (node.isFalse())
* handleFalseLiteral();
* else
* MOZ_NOT_REACHED("boolean literal that's not true or false?");
* }
*/
#if defined(MOZ_NOT_REACHED_MARKER)
# if defined(DEBUG)
# define MOZ_NOT_REACHED(reason) do { \
MOZ_Assert(reason, __FILE__, __LINE__); \
MOZ_NOT_REACHED_MARKER(); \
} while (0)
# else
# define MOZ_NOT_REACHED(reason) MOZ_NOT_REACHED_MARKER()
# endif
#else
# if defined(__GNUC__)
/*
* On older versions of gcc we need to call a noreturn function to mark the
* code as unreachable. Since what we want is an unreachable version of
* MOZ_Assert, we use an asm label
* (http://gcc.gnu.org/onlinedocs/gcc-4.6.2/gcc/Asm-Labels.html) to create
* a new declaration to the same symbol. MOZ_ASSERT_NR should only be
* used via this macro, as it is a very specific hack to older versions of
* gcc.
*/
# define MOZ_GETASMPREFIX2(X) #X
# define MOZ_GETASMPREFIX(X) MOZ_GETASMPREFIX2(X)
# define MOZ_ASMPREFIX MOZ_GETASMPREFIX(__USER_LABEL_PREFIX__)
extern MOZ_NORETURN MFBT_API(void)
MOZ_ASSERT_NR(const char* s, const char* file, int ln) \
asm (MOZ_ASMPREFIX "MOZ_Assert");
# define MOZ_NOT_REACHED(reason) MOZ_ASSERT_NR(reason, __FILE__, __LINE__)
# elif defined(DEBUG)
# define MOZ_NOT_REACHED(reason) MOZ_Assert(reason, __FILE__, __LINE__)
# else
# define MOZ_NOT_REACHED(reason) ((void)0)
# endif
#endif
/*
* MOZ_ALWAYS_TRUE(expr) and MOZ_ALWAYS_FALSE(expr) always evaluate the provided
* expression, in debug builds and in release builds both. Then, in debug
* builds only, the value of the expression is asserted either true or false
* using MOZ_ASSERT.
*/
#ifdef DEBUG
# define MOZ_ALWAYS_TRUE(expr) MOZ_ASSERT((expr))
# define MOZ_ALWAYS_FALSE(expr) MOZ_ASSERT(!(expr))
#else
# define MOZ_ALWAYS_TRUE(expr) ((void)(expr))
# define MOZ_ALWAYS_FALSE(expr) ((void)(expr))
#endif
#endif /* mozilla_Assertions_h_ */
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