[1/3] RFC: add static_assert macro

[Tom Tromey]

In the absence of comments I plan to check this in.

This adds a static_assert macro to gdb_assert.h and changes some code in
MI to use this rather than a runtime check.

I just noticed this in passing, and it seemed like a good cleanup.
Static checks, when possible, are preferable to dynamic ones.

Tom

2011-11-16  Tom Tromey  <tromey@redhat.com>

	* mi/mi-common.c (_initialize_gdb_mi_common): Remove.
	Use static_assert to check the size of
	async_reason_string_lookup.
	* common/gdb_assert.h (static_assert): New macro.

>From a0751874af42798aa7ec8c21707c1503af017a14 Mon Sep 17 00:00:00 2001
From: Tom Tromey <tromey@redhat.com>
Date: Tue, 15 Nov 2011 14:37:46 -0700
Subject: [PATCH 1/3] add static_assert and change MI to use it

---
 gdb/ChangeLog           |    7 +++++++
 gdb/common/gdb_assert.h |    6 ++++++
 gdb/mi/mi-common.c      |   14 +++-----------
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/gdb/common/gdb_assert.h b/gdb/common/gdb_assert.h
index 634049e..de1a1c9 100644
--- a/gdb/common/gdb_assert.h
+++ b/gdb/common/gdb_assert.h
@@ -20,6 +20,12 @@
 #ifndef GDB_ASSERT_H
 #define GDB_ASSERT_H
 
+/* A static assertion.  This will cause a compile-time error if EXPR,
+   which must be a compile-time constant, is false.  */
+
+#define static_assert(expr) \
+  extern int never_defined_just_used_for_checking[(expr) ? 1 : -1]
+
 /* PRAGMATICS: "gdb_assert.h":gdb_assert() is a lower case (rather
    than upper case) macro since that provides the closest fit to the
    existing lower case macro <assert.h>:assert() that it is
diff --git a/gdb/mi/mi-common.c b/gdb/mi/mi-common.c
index ab126f6..e7dd3c4 100644
--- a/gdb/mi/mi-common.c
+++ b/gdb/mi/mi-common.c
@@ -18,6 +18,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
+#include "gdb_assert.h"
 #include "mi-common.h"
 
 static const char * const async_reason_string_lookup[] =
@@ -37,19 +38,10 @@ static const char * const async_reason_string_lookup[] =
   NULL
 };
 
+static_assert (ARRAY_SIZE (async_reason_string_lookup) == EXEC_ASYNC_LAST + 1);
+
 const char *
 async_reason_lookup (enum async_reply_reason reason)
 {
   return async_reason_string_lookup[reason];
 }
-
-/* Provide a prototype to silence -Wmissing-prototypes.  */
-extern initialize_file_ftype _initialize_gdb_mi_common;
-
-void
-_initialize_gdb_mi_common (void)
-{
-  if (ARRAY_SIZE (async_reason_string_lookup) != EXEC_ASYNC_LAST + 1)
-    internal_error (__FILE__, __LINE__,
-		    _("async_reason_string_lookup is inconsistent"));
-}
-- 
1.7.6.4