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Diffstat (limited to 'lib/stdcountof.in.h')
| -rw-r--r-- | lib/stdcountof.in.h | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/lib/stdcountof.in.h b/lib/stdcountof.in.h new file mode 100644 index 00000000000..c2de1adce8b --- /dev/null +++ b/lib/stdcountof.in.h @@ -0,0 +1,124 @@ +/* Copyright 2025-2026 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published + by the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + 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 Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Bruno Haible <bruno@clisp.org>, 2025. */ + +#ifndef _@GUARD_PREFIX@_STDCOUNTOF_H + +#if __GNUC__ >= 3 +@PRAGMA_SYSTEM_HEADER@ +#endif +@PRAGMA_COLUMNS@ + +/* The include_next requires a split double-inclusion guard. */ +#if (defined __cplusplus ? @CXX_HAVE_STDCOUNTOF_H@ : @HAVE_STDCOUNTOF_H@) +# @INCLUDE_NEXT@ @NEXT_STDCOUNTOF_H@ +#else + +#ifndef _@GUARD_PREFIX@_STDCOUNTOF_H +#define _@GUARD_PREFIX@_STDCOUNTOF_H + +/* This file uses _GL_GNUC_PREREQ. */ +#if !_GL_CONFIG_H_INCLUDED + #error "Please include config.h first." +#endif + +/* Get size_t. */ +#include <stddef.h> + +/* Returns the number of elements of the array A, as a value of type size_t. + + Example declarations of arrays: + extern int a[]; + extern int a[10]; + static int a[10][20]; + void func () { int a[10]; ... } + It works for arrays that are declared outside functions and for local + variables of array type. It does *not* work for function parameters + of array type, because they are actually parameters of pointer type. + In this case, i.e. if A is a pointer, e.g. in + void func (int a[10]) { ... } + this macro attempts to produce an error. + */ +#define countof(...) \ + ((size_t) (sizeof (__VA_ARGS__) / sizeof (__VA_ARGS__)[0] \ + + 0 * _gl_verify_is_array (__VA_ARGS__))) + +/* Attempts to verify that A is an array. */ +#if defined __cplusplus +/* Borrowed from verify.h. */ +# if !GNULIB_defined_struct__gl_verify_type +template <int w> + struct _gl_verify_type { + unsigned int _gl_verify_error_if_negative: w; + }; +# define GNULIB_defined_struct__gl_verify_type 1 +# endif +# if __cplusplus >= 201103L +# if 1 + /* Use decltype. */ +/* Default case. */ +template <typename T> + struct _gl_array_type_test { static const int is_array = -1; }; +/* Unbounded arrays. */ +template <typename T> + struct _gl_array_type_test<T[]> { static const int is_array = 1; }; +/* Bounded arrays. */ +template <typename T, size_t N> + struct _gl_array_type_test<T[N]> { static const int is_array = 1; }; +/* String literals. */ +template <typename T, size_t N> + struct _gl_array_type_test<T const (&)[N]> { static const int is_array = 1; }; +# define _gl_verify_is_array(...) \ + sizeof (_gl_verify_type<_gl_array_type_test<decltype(__VA_ARGS__)>::is_array>) +# else + /* Use template argument deduction. + Use sizeof to get a constant expression from an unknown type. + Note: This approach does not work for countof (((int[]) { a, b, c })). */ +/* Default case. */ +template <typename T> + struct _gl_array_type_test { double large; }; +/* Unbounded arrays. */ +template <typename T> + struct _gl_array_type_test<T[]> { char small; }; +/* Bounded arrays. */ +template <typename T, size_t N> + struct _gl_array_type_test<T[N]> { char small; }; +/* The T& parameter is essential here: it prevents decay (array-to-pointer + conversion). */ +template <typename T> _gl_array_type_test<T> _gl_array_type_test_helper(T&); +# define _gl_verify_is_array(...) \ + sizeof (_gl_verify_type<(sizeof (_gl_array_type_test_helper(__VA_ARGS__)) < sizeof (double) ? 1 : -1)>) +# endif +# else +/* The compiler does not have the necessary functionality. */ +# define _gl_verify_is_array(...) 0 +# endif +#else +/* In C, we can use typeof and __builtin_types_compatible_p. */ +/* Work around clang bug <https://github.com/llvm/llvm-project/issues/143284>. */ +# if (_GL_GNUC_PREREQ (3, 1) && ! defined __clang__ /* || defined __clang__ */) \ + && !(defined __STRICT_ANSI__ && __STDC_VERSION__ < 202311L) /* but not with -std=c99 or -std=c11 */ +# define _gl_verify_is_array(...) \ + sizeof (struct { unsigned int _gl_verify_error_if_negative : __builtin_types_compatible_p (typeof (__VA_ARGS__), typeof (&*(__VA_ARGS__))) ? -1 : 1; }) +# else +/* The compiler does not have the necessary built-ins. */ +# define _gl_verify_is_array(...) 0 +# endif +#endif + +#endif /* _@GUARD_PREFIX@_STDCOUNTOF_H */ +#endif +#endif /* _@GUARD_PREFIX@_STDCOUNTOF_H */ |