summaryrefslogtreecommitdiff
path: root/lib/verify.h
diff options
context:
space:
mode:
Diffstat (limited to 'lib/verify.h')
-rw-r--r--lib/verify.h217
1 files changed, 39 insertions, 178 deletions
diff --git a/lib/verify.h b/lib/verify.h
index db52900e..7773c794 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -1,6 +1,6 @@
/* Compile-time assert-like macros.
- Copyright (C) 2005-2006, 2009-2015 Free Software Foundation, Inc.
+ Copyright (C) 2005-2006, 2009-2010 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
@@ -17,49 +17,21 @@
/* 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 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 works as per C++11.
- This will likely be supported by future GCC versions, in C++ mode.
-
- 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
-#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
+#ifndef VERIFY_H
+# define VERIFY_H 1
/* 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.
+ There are two macros, since no single macro can be used in all
+ contexts in C. verify_true (R) is for scalar contexts, including
+ integer constant expression contexts. verify (R) is for declaration
+ contexts, e.g., the top level.
+
+ Symbols ending in "__" are private to this header.
- The code below uses several ideas for C++ compilers, and for C
- compilers that do not support _Static_assert:
+ The code below uses several ideas.
* The first step is ((R) ? 1 : -1). Given an expression R, of
integral or boolean or floating-point type, this yields an
@@ -67,9 +39,7 @@
constant and nonnegative.
* Next this expression W is wrapped in a type
- struct _gl_verify_type {
- unsigned int _gl_verify_error_if_negative: W;
- }.
+ struct verify_type__ { unsigned int verify_error_if_negative_size__: W; }.
If W is negative, this yields a compile-time error. No compiler can
deal with a bit-field of negative size.
@@ -83,7 +53,7 @@
void function (int n) { verify (n < 0); }
- * For the verify macro, the struct _gl_verify_type will need to
+ * For the verify macro, the struct 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,
@@ -99,14 +69,13 @@
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__);
+ #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.)
+ would be the same for both invocations.
A solution is to use the sizeof operator. It yields a number,
getting rid of the identity of the type. Declarations like
@@ -121,11 +90,11 @@
Which of the following alternatives can be used?
extern int dummy [sizeof (struct {...})];
- extern int dummy [sizeof (struct _gl_verify_type {...})];
+ extern int dummy [sizeof (struct verify_type__ {...})];
extern void dummy (int [sizeof (struct {...})]);
- extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
+ extern void dummy (int [sizeof (struct verify_type__ {...})]);
extern int (*dummy (void)) [sizeof (struct {...})];
- extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})];
+ extern int (*dummy (void)) [sizeof (struct verify_type__ {...})];
In the second and sixth case, the struct type is exported to the
outer scope; two such declarations therefore collide. GCC warns
@@ -134,146 +103,38 @@
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 GCC does not warn about
+ the last declaration mentioned above. If a future version of GCC
+ introduces a warning for this, the problem could be worked around
+ by using code specialized to GCC, e.g.,:
- * 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.
+ #if 4 <= __GNUC__
+ # define verify(R) \
+ extern int (* verify_function__ (void)) \
+ [__builtin_constant_p (R) && (R) ? 1 : -1]
+ #endif
* 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)))
+/* Verify requirement R at compile-time, as an integer constant expression.
+ Return 1. */
-#ifdef __cplusplus
-# if !GNULIB_defined_struct__gl_verify_type
+# ifdef __cplusplus
template <int w>
- struct _gl_verify_type {
- unsigned int _gl_verify_error_if_negative: w;
- };
-# define GNULIB_defined_struct__gl_verify_type 1
+ struct verify_type__ { unsigned int verify_error_if_negative_size__: w; };
+# define verify_true(R) \
+ (!!sizeof (verify_type__<(R) ? 1 : -1>))
+# else
+# define verify_true(R) \
+ (!!sizeof \
+ (struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -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, preferably
- with a diagnostic that includes the string-literal DIAGNOSTIC.
-
- 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
-#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_ASSERT && !defined _Static_assert
-# define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
-# endif
-# if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert
-# define static_assert _Static_assert /* C11 requires this #define. */
-# endif
-#endif
-
-/* @assert.h omit start@ */
-
-/* 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
- 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. */
-
-#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 ';'. */
-#define verify(R) _GL_VERIFY (R, "verify (" #R ")")
-
-#ifndef __has_builtin
-# define __has_builtin(x) 0
-#endif
-
-/* 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. */
-
-#if (__has_builtin (__builtin_unreachable) \
- || 4 < __GNUC__ + (5 <= __GNUC_MINOR__))
-# define assume(R) ((R) ? (void) 0 : __builtin_unreachable ())
-#elif 1200 <= _MSC_VER
-# define assume(R) __assume (R)
-#elif (defined lint \
- && (__has_builtin (__builtin_trap) \
- || 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__))))
- /* 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)))
-#endif
-
-/* @assert.h omit end@ */
+# define verify(R) extern int (* verify_function__ (void)) [verify_true (R)]
#endif