diff options
Diffstat (limited to 'lib/verify.h')
| -rw-r--r-- | lib/verify.h | 162 |
1 files changed, 92 insertions, 70 deletions
diff --git a/lib/verify.h b/lib/verify.h index a3b2a2d6..07b2f486 100644 --- a/lib/verify.h +++ b/lib/verify.h @@ -1,27 +1,18 @@ /* Compile-time assert-like macros. - Copyright (C) 2005-2006, 2009-2018 Free Software Foundation, Inc. + Copyright (C) 2005-2006, 2009-2022 Free Software Foundation, Inc. - This program is free software: you can redistribute it and/or - modify it under the terms of either: + This file 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. - * the GNU Lesser General Public License as published by the Free - Software Foundation; either version 3 of the License, or (at your - option) any later version. - - or - - * the GNU General Public License as published by the Free - Software Foundation; either version 2 of the License, or (at your - option) any later version. - - or both in parallel, as here. - This program is distributed in the hope that it will be useful, + This file 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. + GNU Lesser General Public License for more details. - You should have received a copy of the GNU General Public License + 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 Paul Eggert, Bruno Haible, and Jim Meyering. */ @@ -30,31 +21,32 @@ #define _GL_VERIFY_H -/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per C11. - This is supported by GCC 4.6.0 and later, in C mode, and its use - here generates easier-to-read diagnostics when verify (R) fails. +/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert (R, DIAGNOSTIC) + works as per C11. This is supported by GCC 4.6.0+ and by clang 4+. - Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per C++11. - This will likely be supported by future GCC versions, in C++ mode. + Define _GL_HAVE__STATIC_ASSERT1 to 1 if _Static_assert (R) works as + per C2x. This is supported by GCC 9.1+. - Use this only with GCC. If we were willing to slow 'configure' - down we could also use it with other compilers, but since this - affects only the quality of diagnostics, why bother? */ -#if (4 < __GNUC__ + (6 <= __GNUC_MINOR__) \ - && (201112L <= __STDC_VERSION__ || !defined __STRICT_ANSI__) \ - && !defined __cplusplus) -# define _GL_HAVE__STATIC_ASSERT 1 -#endif -/* The condition (99 < __GNUC__) is temporary, until we know about the - first G++ release that supports static_assert. */ -#if (99 < __GNUC__) && defined __cplusplus -# define _GL_HAVE_STATIC_ASSERT 1 + Support compilers claiming conformance to the relevant standard, + and also support GCC when not pedantic. If we were willing to slow + 'configure' down we could also use it with other compilers, but + since this affects only the quality of diagnostics, why bother? */ +#ifndef __cplusplus +# if (201112L <= __STDC_VERSION__ \ + || (!defined __STRICT_ANSI__ \ + && (4 < __GNUC__ + (6 <= __GNUC_MINOR__) || 4 <= __clang_major__))) +# define _GL_HAVE__STATIC_ASSERT 1 +# endif +# if (202000L <= __STDC_VERSION__ \ + || (!defined __STRICT_ANSI__ && 9 <= __GNUC__)) +# define _GL_HAVE__STATIC_ASSERT1 1 +# endif #endif /* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other system headers, defines a conflicting _Static_assert that is no better than ours; override it. */ -#ifndef _GL_HAVE_STATIC_ASSERT +#ifndef _GL_HAVE__STATIC_ASSERT # include <stddef.h> # undef _Static_assert #endif @@ -152,9 +144,9 @@ which do not support _Static_assert, also do not warn about the last declaration mentioned above. - * GCC warns if -Wnested-externs is enabled and verify() is used + * GCC warns if -Wnested-externs is enabled and 'verify' is used within a function body; but inside a function, you can always - arrange to use verify_expr() instead. + arrange to use verify_expr instead. * In C++, any struct definition inside sizeof is invalid. Use a template type to work around the problem. */ @@ -206,48 +198,63 @@ template <int w> #endif /* Verify requirement R at compile-time, as a declaration without a - trailing ';'. If R is false, fail at compile-time, preferably - with a diagnostic that includes the string-literal DIAGNOSTIC. + trailing ';'. If R is false, fail at compile-time. + + This macro requires three or more arguments but uses at most the first + two, so that the _Static_assert macro optionally defined below supports + both the C11 two-argument syntax and the C2x one-argument syntax. Unfortunately, unlike C11, this implementation must appear as an ordinary declaration, and cannot appear inside struct { ... }. */ -#ifdef _GL_HAVE__STATIC_ASSERT -# define _GL_VERIFY _Static_assert +#if 200410 <= __cpp_static_assert +# define _GL_VERIFY(R, DIAGNOSTIC, ...) static_assert (R, DIAGNOSTIC) +#elif defined _GL_HAVE__STATIC_ASSERT +# define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC) #else -# define _GL_VERIFY(R, DIAGNOSTIC) \ +# define _GL_VERIFY(R, DIAGNOSTIC, ...) \ extern int (*_GL_GENSYM (_gl_verify_function) (void)) \ [_GL_VERIFY_TRUE (R, DIAGNOSTIC)] #endif /* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h. */ #ifdef _GL_STATIC_ASSERT_H -# if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert -# define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC) +# if !defined _GL_HAVE__STATIC_ASSERT1 && !defined _Static_assert +# define _Static_assert(...) \ + _GL_VERIFY (__VA_ARGS__, "static assertion failed", -) # endif -# if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert +# if __cpp_static_assert < 201411 && !defined static_assert # define static_assert _Static_assert /* C11 requires this #define. */ # endif #endif /* @assert.h omit start@ */ +#if 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__)) +# define _GL_HAS_BUILTIN_TRAP 1 +#elif defined __has_builtin +# define _GL_HAS_BUILTIN_TRAP __has_builtin (__builtin_trap) +#else +# define _GL_HAS_BUILTIN_TRAP 0 +#endif + +#if 4 < __GNUC__ + (5 <= __GNUC_MINOR__) +# define _GL_HAS_BUILTIN_UNREACHABLE 1 +#elif defined __has_builtin +# define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable) +#else +# define _GL_HAS_BUILTIN_UNREACHABLE 0 +#endif + /* Each of these macros verifies that its argument R is nonzero. To be portable, R should be an integer constant expression. Unlike assert (R), there is no run-time overhead. There are two macros, since no single macro can be used in all - contexts in C. verify_true (R) is for scalar contexts, including + contexts in C. verify_expr (R, E) is for scalar contexts, including integer constant expression contexts. verify (R) is for declaration contexts, e.g., the top level. */ -/* Verify requirement R at compile-time, as an integer constant expression. - Return 1. This is equivalent to verify_expr (R, 1). - - verify_true is obsolescent; please use verify_expr instead. */ - -#define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")") - /* Verify requirement R at compile-time. Return the value of the expression E. */ @@ -255,37 +262,52 @@ template <int w> (_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E)) /* Verify requirement R at compile-time, as a declaration without a - trailing ';'. */ + trailing ';'. verify (R) acts like static_assert (R) except that + it is portable to C11/C++14 and earlier, it can issue better + diagnostics, and its name is shorter and may be more convenient. */ -#ifdef __GNUC__ -# define verify(R) _GL_VERIFY (R, "verify (" #R ")") +#ifdef __PGI +/* PGI barfs if R is long. */ +# define verify(R) _GL_VERIFY (R, "verify (...)", -) #else -/* PGI barfs if R is long. Play it safe. */ -# define verify(R) _GL_VERIFY (R, "verify (...)") +# define verify(R) _GL_VERIFY (R, "verify (" #R ")", -) #endif -#ifndef __has_builtin -# define __has_builtin(x) 0 -#endif +/* Assume that R always holds. Behavior is undefined if R is false, + fails to evaluate, or has side effects. + + 'assume (R)' is a directive from the programmer telling the + compiler that R is true so the compiler needn't generate code to + test R. This is why 'assume' is in verify.h: it's related to + static checking (in this case, static checking done by the + programmer), not dynamic checking. + + 'assume (R)' can affect compilation of all the code, not just code + that happens to be executed after the assume (R) is "executed". + For example, if the code mistakenly does 'assert (R); assume (R);' + the compiler is entitled to optimize away the 'assert (R)'. + + Although assuming R can help a compiler generate better code or + diagnostics, performance can suffer if R uses hard-to-optimize + features such as function calls not inlined by the compiler. -/* Assume that R always holds. This lets the compiler optimize - accordingly. R should not have side-effects; it may or may not be - evaluated. Behavior is undefined if R is false. */ + Avoid Clang's __builtin_assume, as it breaks GNU Emacs master + as of 2020-08-23T21:09:49Z!eggert@cs.ucla.edu; see + <https://bugs.gnu.org/43152#71>. It's not known whether this breakage + is a Clang bug or an Emacs bug; play it safe for now. */ -#if (__has_builtin (__builtin_unreachable) \ - || 4 < __GNUC__ + (5 <= __GNUC_MINOR__)) +#if _GL_HAS_BUILTIN_UNREACHABLE # define assume(R) ((R) ? (void) 0 : __builtin_unreachable ()) #elif 1200 <= _MSC_VER # define assume(R) __assume (R) -#elif ((defined GCC_LINT || defined lint) \ - && (__has_builtin (__builtin_trap) \ - || 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__)))) +#elif (defined GCC_LINT || defined lint) && _GL_HAS_BUILTIN_TRAP /* Doing it this way helps various packages when configured with --enable-gcc-warnings, which compiles with -Dlint. It's nicer when 'assume' silences warnings even with older GCCs. */ # define assume(R) ((R) ? (void) 0 : __builtin_trap ()) #else -# define assume(R) ((void) (0 && (R))) + /* Some tools grok NOTREACHED, e.g., Oracle Studio 12.6. */ +# define assume(R) ((R) ? (void) 0 : /*NOTREACHED*/ (void) 0) #endif /* @assert.h omit end@ */ |