On 05/05/11 01:10, Bruno Haible wrote:
> - A doc update of doc/posix-headers/assert.texi would be useful.
Thanks for catching that. A further draft patch is below. It also
notes a minor difference between C89 and C99 'assert'.
> Identifiers starting with __ are in the namespace of compiler and libc
> implementation.
Identifiers starting with "_G" are also reserved, and we usurp them,
so I figured we should usurp "__gl_" to be consistent. It's no big
deal, I'll change the __gl_ prefix to a _gl_ prefix. But strictly
speaking, as far as I can see, the following code conforms to draft
C1X:
#define _gl_static_assert_error_if_negative 100
#include <assert.h>
static_assert (1);
and once we change __gl_ to _gl_ this (perverse) code won't work any more.
> - Can the new static_assert be used in an ISO C++ compatible way [1], that is,
> as a member declaration in a struct or class?
Unfortunately not. I noted that in the documentation proposed below.
diff --git a/ChangeLog b/ChangeLog
index 24dd572..4028ea1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -18,6 +18,7 @@
and _Static_assert is not built in.
(verify_true, verify): Define only if _GL_STATIC_ASSERT_H is not
defined, and use the new macros mentioned above.
+ * doc/posix-headers/assert.texi: Document this
2011-05-05 Eric Blake <ebl...@redhat.com>
diff --git a/doc/posix-headers/assert.texi b/doc/posix-headers/assert.texi
index 02a1c3b..aa78ee7 100644
--- a/doc/posix-headers/assert.texi
+++ b/doc/posix-headers/assert.texi
@@ -3,12 +3,31 @@
POSIX specification:@*
@url{http://www.opengroup.org/onlinepubs/9699919799/basedefs/assert.h.html}
-Gnulib module: ---
+Gnulib module: assert-h
+
+See also the Gnulib module @code{assert}.
Portability problems fixed by Gnulib:
@itemize
+@item
+The draft C1X and C++0X @code{static_assert}, and the draft C1X
+@code{_Static_assert}, are not supported by many platforms.
+For example, GCC versions before 4.6.0 do not support @code{_Static_assert},
+and G++ versions through at least 4.6.0 do not support @code{static_assert}.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
+@item
+Draft C1X @code{_Static_assert} and draft C++0X @code{static_assert}
+are keywords that can be used without including @code{<assert.h>}.
+The Gnulib substitutes are macros that require including @code{<assert.h>}.
+@item
+The draft C1X @code{static_assert} and @code{_Static_assert} can also
+be used within a @code{struct} or @code{union} specifier, in place of
+an ordinary declaration of a member of the struct or union. The
+Gnulib substitute can be used only as an ordinary declaration.
+@item
+In C99, @code{assert} can be applied to any scalar expression.
+In C89, the argument to @code{assert} is of type @code{int}.
@end itemize
diff --git a/lib/verify.h b/lib/verify.h
index 39a5ffc..e5065ff 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -59,8 +59,8 @@
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 _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.
@@ -75,7 +75,7 @@
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 _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,
@@ -113,11 +113,11 @@
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 _gl_verify_type {...})];
extern void dummy (int [sizeof (struct {...})]);
- extern void dummy (int [sizeof (struct __gl_verify_type {...})]);
+ extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
extern int (*dummy (void)) [sizeof (struct {...})];
- extern int (*dummy (void)) [sizeof (struct __gl_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
@@ -165,20 +165,20 @@
# ifdef __cplusplus
template <int w>
- struct __gl_verify_type {
- unsigned int __gl_verify_error_if_negative: w;
+ struct _gl_verify_type {
+ unsigned int _gl_verify_error_if_negative: w;
};
# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
- __gl_verify_type<(R) ? 1 : -1>
+ _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; \
+ int _gl_dummy; \
}
# else
# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
- struct { unsigned int __gl_verify_error_if_negative: (R) ? 1 : -1; }
+ struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
# endif
/* Verify requirement R at compile-time, as a declaration without a
@@ -192,17 +192,17 @@ template <int w>
# define _GL_VERIFY _Static_assert
# else
# define _GL_VERIFY(R, DIAGNOSTIC) \
- extern int (*_GL_GENSYM (__gl_verify_function) (void)) \
+ 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 /* Draft C1X requires this #define. */
-# ifndef _GL_HAVE__STATIC_ASSERT
-# define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
-# endif
# endif
# else
diff --git a/modules/assert-h b/modules/assert-h
index eeda888..50bd9f8 100644
--- a/modules/assert-h
+++ b/modules/assert-h
@@ -26,7 +26,7 @@ assert.h: assert.in.h verify.h $(top_builddir)/config.status
-e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \
-e 's|@''NEXT_ASSERT_H''@|$(NEXT_ASSERT_H)|g' \
< $(srcdir)/assert.in.h && \
- sed -e 's|__gl_verify|__gl_static_assert|g' \
+ sed -e 's|_gl_verify|_gl_static_assert|g' \
-e 's|_GL_VERIFY|_GL_STATIC_ASSERT|g' \
< $(srcdir)/verify.h; \
} > $@-t && \
