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Jonathan WakelyandTomasz Kamiński
ea37298b65
C++26 changes assert into a variadic macro to support using
assignment-expressions that would be interpreted as multiple macro
arguments, in particular one containing:
* template parameter lists: func<int, float>()
* calls to overloaded operator[] that accepts multiple arguments: arr[1, 2]
this is C++23 feature, see libstdc++ PR/119855 [1]
* lambdas with explicit captures: [x, y] { ... }
The new expansion in form:
(__VA_ARGS__) ? void (1 ? 1 : bool (__VA_ARGS__))
: __assert_fail (...)
Has the following properties:
* Use of (__VA_ARGS__) ? ... : ..., requires that __VA_ARGS__
is contextually convertible to bool. This means that enumerators
of scoped enumeration are no longer accepted (they are only
explicitly convertible). Thus this patch address the glibc PR/27276 [2].
* Nested ternary 1 ? 1 : bool (__VA_ARGS__) guarantees that
expression expanded from __VA_ARGS__ is not evaluated twice.
This is used instead of unevaluated context (like sizeof...)
to support C++ expressions that are not allowed in unevaluated
context (lambdas until C++20, co_await, co_yield).
* bool (__VA_ARGS__) is ill-formed if __VA_ARGS__ expands to
multiple arguments: assert(1, 2)
* bool (__VA_ARGS__) also triggers warnings when __VA_ARGS__
expands to x = 1: assert(x = 1)
To guarantee that the code snippets from assert/test-assert-c++-variadic.cc,
are actually checked for validity, we need to compile this test in C++26
(-std=c++26) mode. To achieve that, this patch compiles the file with
test-config-cxxflags-stdcxx26 variable as additional flag, that is set to
-std=c++26 if $(TEST_CXX) executable supports that flag, and empty otherwise.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119855
[2] https://sourceware.org/bugzilla/show_bug.cgi?id=27276
Co-authored-by: Tomasz Kamiński <tkaminsk@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
219 lines
7.1 KiB
C++
219 lines
7.1 KiB
C++
/* Copyright (C) 1991-2026 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/*
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* ISO C99 Standard: 7.2 Diagnostics <assert.h>
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*/
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#ifdef _ASSERT_H
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# undef _ASSERT_H
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# undef assert
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# undef __ASSERT_VOID_CAST
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# ifdef __USE_GNU
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# undef assert_perror
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# endif
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#endif /* assert.h */
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#define _ASSERT_H 1
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#include <features.h>
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#if __GLIBC_USE (ISOC23)
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# ifndef __STDC_VERSION_ASSERT_H__
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# define __STDC_VERSION_ASSERT_H__ 202311L
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# endif
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#endif
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#if defined __cplusplus && __GNUC_PREREQ (2,95)
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# define __ASSERT_VOID_CAST static_cast<void>
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#else
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# define __ASSERT_VOID_CAST (void)
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#endif
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/* C23 makes assert a variadic macro so that expressions with a comma
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not between parentheses, but that would still be valid as a single
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function argument, such as those involving compound literals with a
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comma in the initializer list, can be passed to assert. This
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depends on support for variadic macros (added in C99 and GCC 2.95),
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and on support for _Bool (added in C99 and GCC 3.0) in order to
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validate that only a single expression is passed as an argument. */
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#if ((__GLIBC_USE (ISOC23) \
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&& (defined __GNUC__ \
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? __GNUC_PREREQ (3, 0) \
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: defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L)) \
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|| (defined __cplusplus && __cplusplus > 202302L))
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# define __ASSERT_VARIADIC 1
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#else
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# define __ASSERT_VARIADIC 0
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#endif
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/* void assert (int expression);
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If NDEBUG is defined, do nothing.
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If not, and EXPRESSION is zero, print an error message and abort. */
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#ifdef NDEBUG
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# if __ASSERT_VARIADIC
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# define assert(...) (__ASSERT_VOID_CAST (0))
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# else
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# define assert(expr) (__ASSERT_VOID_CAST (0))
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# endif
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/* void assert_perror (int errnum);
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If NDEBUG is defined, do nothing. If not, and ERRNUM is not zero, print an
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error message with the error text for ERRNUM and abort.
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(This is a GNU extension.) */
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# ifdef __USE_GNU
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# define assert_perror(errnum) (__ASSERT_VOID_CAST (0))
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# endif
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#else /* Not NDEBUG. */
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__BEGIN_DECLS
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/* This prints an "Assertion failed" message and aborts. */
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extern void __assert_fail (const char *__assertion, const char *__file,
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unsigned int __line, const char *__function)
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__THROW __attribute__ ((__noreturn__)) __COLD;
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/* Likewise, but prints the error text for ERRNUM. */
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extern void __assert_perror_fail (int __errnum, const char *__file,
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unsigned int __line, const char *__function)
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__THROW __attribute__ ((__noreturn__)) __COLD;
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/* The following is not at all used here but needed for standard
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compliance. */
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extern void __assert (const char *__assertion, const char *__file, int __line)
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__THROW __attribute__ ((__noreturn__)) __COLD;
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# if __ASSERT_VARIADIC && !defined __cplusplus
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/* This function is not defined and is not called outside of an
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unevaluated sizeof, but serves to verify that the argument to
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assert is a single expression. */
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extern _Bool __assert_single_arg (_Bool);
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# endif
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__END_DECLS
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/* When possible, define assert so that it does not add extra
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parentheses around EXPR. Otherwise, those added parentheses would
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suppress warnings we'd expect to be detected by gcc's -Wparentheses. */
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# if defined __cplusplus
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# if defined __has_builtin
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# if __has_builtin (__builtin_FILE)
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# define __ASSERT_FILE __builtin_FILE ()
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# define __ASSERT_LINE __builtin_LINE ()
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# endif
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# endif
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# if !defined __ASSERT_FILE
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# define __ASSERT_FILE __FILE__
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# define __ASSERT_LINE __LINE__
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# endif
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# if __ASSERT_VARIADIC
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/* The first test of __VA_ARGS__ evaluates it without converting scoped
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enumeration values to bool, and the second test checks that it is a
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single expression without evaluating it. */
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# define assert(...) \
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((__VA_ARGS__) \
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? void (1 ? 1 : bool (__VA_ARGS__)) \
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: __assert_fail (#__VA_ARGS__, __ASSERT_FILE, __ASSERT_LINE, \
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__ASSERT_FUNCTION))
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# else
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# define assert(expr) \
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(static_cast <bool> (expr) \
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? void (0) \
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: __assert_fail (#expr, __ASSERT_FILE, __ASSERT_LINE, \
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__ASSERT_FUNCTION))
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# endif
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# elif !defined __GNUC__ || defined __STRICT_ANSI__
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# if __ASSERT_VARIADIC
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# define assert(...) \
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(((void) sizeof (__assert_single_arg (__VA_ARGS__)), __VA_ARGS__) \
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? __ASSERT_VOID_CAST (0) \
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: __assert_fail (#__VA_ARGS__, __FILE__, __LINE__, __ASSERT_FUNCTION))
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# else
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# define assert(expr) \
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((expr) \
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? __ASSERT_VOID_CAST (0) \
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: __assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION))
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# endif
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# else
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# if __ASSERT_VARIADIC
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# define assert(...) \
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((void) sizeof (__assert_single_arg (__VA_ARGS__)), __extension__ ({ \
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if (__VA_ARGS__) \
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; /* empty */ \
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else \
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__assert_fail (#__VA_ARGS__, __FILE__, __LINE__, __ASSERT_FUNCTION); \
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}))
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# else
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/* The first occurrence of EXPR is not evaluated due to the sizeof,
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but will trigger any pedantic warnings masked by the __extension__
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for the second occurrence. The ternary operator is required to
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support function pointers and bit fields in this context, and to
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suppress the evaluation of variable length arrays. */
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# define assert(expr) \
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((void) sizeof ((expr) ? 1 : 0), __extension__ ({ \
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if (expr) \
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; /* empty */ \
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else \
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__assert_fail (#expr, __FILE__, __LINE__, __ASSERT_FUNCTION); \
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}))
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# endif
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# endif
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# ifdef __USE_GNU
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# define assert_perror(errnum) \
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(!(errnum) \
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? __ASSERT_VOID_CAST (0) \
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: __assert_perror_fail ((errnum), __FILE__, __LINE__, __ASSERT_FUNCTION))
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# endif
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/* Version 2.4 and later of GCC define a magical variable `__PRETTY_FUNCTION__'
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which contains the name of the function currently being defined.
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This is broken in G++ before version 2.6.
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C9x has a similar variable called __func__, but prefer the GCC one since
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it demangles C++ function names. */
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# if defined __cplusplus ? __GNUC_PREREQ (2, 6) : __GNUC_PREREQ (2, 4)
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# define __ASSERT_FUNCTION __extension__ __PRETTY_FUNCTION__
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# else
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# if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L
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# define __ASSERT_FUNCTION __func__
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# else
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# define __ASSERT_FUNCTION ((const char *) 0)
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# endif
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# endif
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#endif /* NDEBUG. */
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#if (defined __USE_ISOC11 \
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&& (!defined __STDC_VERSION__ \
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|| __STDC_VERSION__ <= 201710L \
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|| !__GNUC_PREREQ (13, 0)) \
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&& !defined __cplusplus)
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# undef static_assert
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# define static_assert _Static_assert
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#endif
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