assert-h: new module, which supports C1X-style static_assert

* lib/assert.in.h, m4/assert_h.m4, modules/assert-h: New files.
* lib/verify.h: Revamp so that this can be copied into assert.h,
while retaining the ability to use it standalone as before.
Rename private identifiers so as not to encroach on the
standard C namespace, since this is now used by assert.h.
(_GL_VERIFY_TYPE): New macro, factoring out differing parts of
the old verify_true.
(_GL_VERIFY_TRUE): New macro, with much of the contents of
the old verify_true.  Use _GL_VERIFY_TYPE.
(_GL_VERIFY): New macro, with much of the contents of the old verify.
(static_assert): New macro, if _GL_STATIC_ASSERT_H
is defined and static_assert is not; _GL_STATIC_ASSERT_H is
defined when this file is copied into the replacement assert.h.
(_Static_assert): New macro, if _GL_STATIC_ASSERT_H is defined
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.

1 files changed, 20 insertions, 1 deletions

diff --git a/doc/posix-headers/assert.texi b/doc/posix-headers/assert.texi
index 02a1c3b547..aa78ee7bc5 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