mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-16 09:50:25 +00:00
2bba9cd409
This incorporates: 2020-09-05 verify: avoid __builtin_assume 2020-08-30 strerrorname_np: New module 2020-08-26 include_next, stdint, time_rz: Change configure message * lib/gnulib.mk.in: Regenerate. * lib/string.in.h, lib/verify.h, m4/include_next.m4, m4/stdint.m4: * m4/string_h.m4, m4/time_rz.m4: Copy from Gnulib.
332 lines
13 KiB
C++
332 lines
13 KiB
C++
/* Compile-time assert-like macros.
|
|
|
|
Copyright (C) 2005-2006, 2009-2020 Free Software Foundation, Inc.
|
|
|
|
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; either version 3 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 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/>. */
|
|
|
|
/* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
|
|
|
|
#ifndef _GL_VERIFY_H
|
|
#define _GL_VERIFY_H
|
|
|
|
|
|
/* 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 later, in C
|
|
mode, and by clang (also 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 and later, and by clang in
|
|
C++1z mode.
|
|
|
|
Define _GL_HAVE_STATIC_ASSERT1 if static_assert (R) works as per
|
|
C++17. This is supported by GCC 9.1 and later, and by clang in
|
|
C++1z mode.
|
|
|
|
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
|
|
#else
|
|
# if 4 <= __clang_major__
|
|
# define _GL_HAVE__STATIC_ASSERT 1
|
|
# endif
|
|
# if 4 <= __clang_major__ && 201411 <= __cpp_static_assert
|
|
# define _GL_HAVE__STATIC_ASSERT1 1
|
|
# endif
|
|
# if 201703L <= __cplusplus \
|
|
|| 9 <= __GNUC__ \
|
|
|| (4 <= __clang_major__ && 201411 <= __cpp_static_assert)
|
|
# 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
|
|
# include <stddef.h>
|
|
# undef _Static_assert
|
|
#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.
|
|
|
|
If _Static_assert works, verify (R) uses it directly. Similarly,
|
|
_GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct
|
|
that is an operand of sizeof.
|
|
|
|
The code below uses several ideas for C++ compilers, and for C
|
|
compilers that do not support _Static_assert:
|
|
|
|
* The first step is ((R) ? 1 : -1). Given an expression R, of
|
|
integral or boolean or floating-point type, this yields an
|
|
expression of integral type, whose value is later verified to be
|
|
constant and nonnegative.
|
|
|
|
* Next this expression W is wrapped in a type
|
|
struct _gl_verify_type {
|
|
unsigned int _gl_verify_error_if_negative: W;
|
|
}.
|
|
If W is negative, this yields a compile-time error. No compiler can
|
|
deal with a bit-field of negative size.
|
|
|
|
One might think that an array size check would have the same
|
|
effect, that is, that the type struct { unsigned int dummy[W]; }
|
|
would work as well. However, inside a function, some compilers
|
|
(such as C++ compilers and GNU C) allow local parameters and
|
|
variables inside array size expressions. With these compilers,
|
|
an array size check would not properly diagnose this misuse of
|
|
the verify macro:
|
|
|
|
void function (int n) { verify (n < 0); }
|
|
|
|
* For the verify macro, the struct _gl_verify_type will need to
|
|
somehow be embedded into a declaration. To be portable, this
|
|
declaration must declare an object, a constant, a function, or a
|
|
typedef name. If the declared entity uses the type directly,
|
|
such as in
|
|
|
|
struct dummy {...};
|
|
typedef struct {...} dummy;
|
|
extern struct {...} *dummy;
|
|
extern void dummy (struct {...} *);
|
|
extern struct {...} *dummy (void);
|
|
|
|
two uses of the verify macro would yield colliding declarations
|
|
if the entity names are not disambiguated. A workaround is to
|
|
attach the current line number to the entity name:
|
|
|
|
#define _GL_CONCAT0(x, y) x##y
|
|
#define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
|
|
extern struct {...} * _GL_CONCAT (dummy, __LINE__);
|
|
|
|
But this has the problem that two invocations of verify from
|
|
within the same macro would collide, since the __LINE__ value
|
|
would be the same for both invocations. (The GCC __COUNTER__
|
|
macro solves this problem, but is not portable.)
|
|
|
|
A solution is to use the sizeof operator. It yields a number,
|
|
getting rid of the identity of the type. Declarations like
|
|
|
|
extern int dummy [sizeof (struct {...})];
|
|
extern void dummy (int [sizeof (struct {...})]);
|
|
extern int (*dummy (void)) [sizeof (struct {...})];
|
|
|
|
can be repeated.
|
|
|
|
* Should the implementation use a named struct or an unnamed struct?
|
|
Which of the following alternatives can be used?
|
|
|
|
extern int dummy [sizeof (struct {...})];
|
|
extern int dummy [sizeof (struct _gl_verify_type {...})];
|
|
extern void dummy (int [sizeof (struct {...})]);
|
|
extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
|
|
extern int (*dummy (void)) [sizeof (struct {...})];
|
|
extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})];
|
|
|
|
In the second and sixth case, the struct type is exported to the
|
|
outer scope; two such declarations therefore collide. GCC warns
|
|
about the first, third, and fourth cases. So the only remaining
|
|
possibility is the fifth case:
|
|
|
|
extern int (*dummy (void)) [sizeof (struct {...})];
|
|
|
|
* GCC warns about duplicate declarations of the dummy function if
|
|
-Wredundant-decls is used. GCC 4.3 and later have a builtin
|
|
__COUNTER__ macro that can let us generate unique identifiers for
|
|
each dummy function, to suppress this warning.
|
|
|
|
* This implementation exploits the fact that older versions of GCC,
|
|
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
|
|
within a function body; but inside a function, you can always
|
|
arrange to use verify_expr instead.
|
|
|
|
* In C++, any struct definition inside sizeof is invalid.
|
|
Use a template type to work around the problem. */
|
|
|
|
/* Concatenate two preprocessor tokens. */
|
|
#define _GL_CONCAT(x, y) _GL_CONCAT0 (x, y)
|
|
#define _GL_CONCAT0(x, y) x##y
|
|
|
|
/* _GL_COUNTER is an integer, preferably one that changes each time we
|
|
use it. Use __COUNTER__ if it works, falling back on __LINE__
|
|
otherwise. __LINE__ isn't perfect, but it's better than a
|
|
constant. */
|
|
#if defined __COUNTER__ && __COUNTER__ != __COUNTER__
|
|
# define _GL_COUNTER __COUNTER__
|
|
#else
|
|
# define _GL_COUNTER __LINE__
|
|
#endif
|
|
|
|
/* Generate a symbol with the given prefix, making it unique if
|
|
possible. */
|
|
#define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
|
|
|
|
/* Verify requirement R at compile-time, as an integer constant expression
|
|
that returns 1. If R is false, fail at compile-time, preferably
|
|
with a diagnostic that includes the string-literal DIAGNOSTIC. */
|
|
|
|
#define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
|
|
(!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC)))
|
|
|
|
#ifdef __cplusplus
|
|
# 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
|
|
# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
|
|
_gl_verify_type<(R) ? 1 : -1>
|
|
#elif defined _GL_HAVE__STATIC_ASSERT
|
|
# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
|
|
struct { \
|
|
_Static_assert (R, DIAGNOSTIC); \
|
|
int _gl_dummy; \
|
|
}
|
|
#else
|
|
# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
|
|
struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
|
|
#endif
|
|
|
|
/* Verify requirement R at compile-time, as a declaration without a
|
|
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 { ... }. */
|
|
|
|
#if defined _GL_HAVE__STATIC_ASSERT
|
|
# define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
|
|
#else
|
|
# 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_ASSERT1 && !defined _Static_assert
|
|
# define _Static_assert(...) \
|
|
_GL_VERIFY (__VA_ARGS__, "static assertion failed", -)
|
|
# endif
|
|
# if !defined _GL_HAVE_STATIC_ASSERT1 && !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_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. Return the value of the
|
|
expression E. */
|
|
|
|
#define verify_expr(R, E) \
|
|
(_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E))
|
|
|
|
/* Verify requirement R at compile-time, as a declaration without a
|
|
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 __PGI
|
|
/* PGI barfs if R is long. */
|
|
# define verify(R) _GL_VERIFY (R, "verify (...)", -)
|
|
#else
|
|
# define verify(R) _GL_VERIFY (R, "verify (" #R ")", -)
|
|
#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.
|
|
|
|
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 _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) && _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
|
|
/* Some tools grok NOTREACHED, e.g., Oracle Studio 12.6. */
|
|
# define assume(R) ((R) ? (void) 0 : /*NOTREACHED*/ (void) 0)
|
|
#endif
|
|
|
|
/* @assert.h omit end@ */
|
|
|
|
#endif
|