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Merge from gnulib.
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@eggert
eggert committed May 6, 2011
1 parent b132939 commit 61b3aff
Showing 1 changed file with 79 additions and 51 deletions.
130 changes: 79 additions & 51 deletions lib/verify.h
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Expand Up @@ -17,42 +17,37 @@

/* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */

#ifndef VERIFY_H
# define VERIFY_H 1
#ifndef _GL_VERIFY_H
# define _GL_VERIFY_H

/* Define HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the

/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the
C1X draft N1548 section 6.7.10. 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 HAVE_STATIC_ASSERT to 1 if static_assert works as per the
C1X draft N1548 section 7.2 or the C++0X draft N3242 section 7.(4).
Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per the
C++0X draft N3242 section 7.(4).
This will likely be supported by future GCC versions, in C++ mode.
For now, use this only with GCC. Eventually whether _Static_assert
and static_assert works should be determined by 'configure'. */
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__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus
# define HAVE__STATIC_ASSERT 1
# 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 HAVE_STATIC_ASSERT 1
# define _GL_HAVE_STATIC_ASSERT 1
# 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
integer constant expression contexts. verify (R) is for declaration
contexts, e.g., the top level.
Symbols ending in "__" are private to this header.
If _Static_assert works, verify (R) uses it directly. Similarly,
verify_true (R) works by packaging a _Static_assert inside a struct
_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
Expand All @@ -64,7 +59,9 @@
constant and nonnegative.
* Next this expression W is wrapped in a type
struct verify_type__ { unsigned int verify_error_if_negative_size__: W; }.
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.
Expand All @@ -78,7 +75,7 @@
void function (int n) { verify (n < 0); }
* For the verify macro, the struct verify_type__ will need to
* 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,
Expand Down Expand Up @@ -116,11 +113,11 @@
Which of the following alternatives can be used?
extern int dummy [sizeof (struct {...})];
extern int dummy [sizeof (struct verify_type__ {...})];
extern int dummy [sizeof (struct _gl_verify_type {...})];
extern void dummy (int [sizeof (struct {...})]);
extern void dummy (int [sizeof (struct verify_type__ {...})]);
extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
extern int (*dummy (void)) [sizeof (struct {...})];
extern int (*dummy (void)) [sizeof (struct verify_type__ {...})];
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
Expand Down Expand Up @@ -159,44 +156,75 @@
possible. */
# define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)

/* Verify requirement R at compile-time, as an integer constant expression.
Return 1. */
/* 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
template <int w>
struct verify_type__ { unsigned int verify_error_if_negative_size__: w; };
# define verify_true(R) \
(!!sizeof (verify_type__<(R) ? 1 : -1>))
# elif HAVE__STATIC_ASSERT
# define verify_true(R) \
(!!sizeof \
(struct { \
_Static_assert (R, "verify_true (" #R ")"); \
int verify_dummy__; \
}))
# elif HAVE_STATIC_ASSERT
# define verify_true(R) \
(!!sizeof \
(struct { \
static_assert (R, "verify_true (" #R ")"); \
int verify_dummy__; \
}))
struct _gl_verify_type {
unsigned int _gl_verify_error_if_negative: w;
};
# 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 verify_true(R) \
(!!sizeof \
(struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -1; }))
# 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 ';'. */
trailing ';'. If R is false, fail at compile-time, preferably
with a diagnostic that includes the string-literal DIAGNOSTIC.
Unfortunately, unlike C1X, 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

# if HAVE__STATIC_ASSERT
# define verify(R) _Static_assert (R, "verify (" #R ")")
# elif HAVE_STATIC_ASSERT
# define verify(R) static_assert (R, "verify (" #R ")")
/* _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 /* Draft C1X requires this #define. */
# endif
# else
# define verify(R) \
extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)]

/* 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. */

# define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")")

/* Verify requirement R at compile-time, as a declaration without a
trailing ';'. */

# define verify(R) _GL_VERIFY (R, "verify (" #R ")")

# endif

#endif

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