along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+/* Written by Paul Eggert and Jim Meyering. */
+
#ifndef VERIFY_H
# define VERIFY_H 1
-# ifndef verify_decl
-# define GL_CONCAT0(x, y) x##y
-# define GL_CONCAT(x, y) GL_CONCAT0 (x, y)
-
-/* Verify requirement, R, at compile-time, as a declaration.
- The implementation uses a struct declaration whose name includes the
- expansion of __LINE__, so there is a small chance that two uses of
- verify_decl from different files will end up colliding (for example,
- f.c includes f.h and verify_decl is used on the same line in each). */
-# define verify_decl(R) \
- struct GL_CONCAT (ct_assert_, __LINE__) { char a[(R) ? 1 : -1]; }
-# endif
-
-/* Verify requirement, R, at compile-time, as an expression.
- Unlike assert, there is no run-time overhead. Unlike verify_decl,
- above, there is no risk of collision, since there is no declared name.
- This macro may be used in some contexts where the other may not, and
- vice versa. Return void. */
-# undef verify
-# define verify(R) ((void) sizeof (struct { char a[(R) ? 1 : -1]; }))
+# define GL_CONCAT0(x, y) x##y
+# define GL_CONCAT(x, y) GL_CONCAT0 (x, y)
+
+/* A type that is valid if and only R is nonzero.
+ R should be an integer constant expression.
+ verify_type__ and verify_error_if_negative_size__ are symbols that
+ are private to this header file. */
+
+# define verify_type__(R) \
+ struct { int verify_error_if_negative_size__[(R) ? 1 : -1]; }
+
+/* Verify requirement R at compile-time, as a declaration.
+ R should be an integer constant expression.
+ Unlike assert, there is no run-time overhead.
+
+ The implementation uses __LINE__ to lessen the probability of
+ generating a warning that verify_function_NNN is multiply declared.
+ However, even if two declarations in different files have the same
+ __LINE__, the multiple declarations are still valid C89 and C99
+ code because they simply redeclare the same external function, so
+ no conforming compiler will reject them outright. */
+
+# define verify(R) \
+ extern verify_type__ (R) GL_CONCAT (verify_function_, __LINE__) (void)
+
+/* Verify requirement R at compile-time, as an expression.
+ R should be an integer constant expression.
+ Unlike assert, there is no run-time overhead.
+ This macro can be used in some contexts where verify cannot, and vice versa.
+ Return void. */
+
+# define verify_expr(R) ((void) sizeof (verify_type__ (R)))
#endif