Bruno Haible <[EMAIL PROTECTED]> writes:
> If we can get away without this restriction, we should.
I agree, but like Jim I'd rather avoid the Autoconf test if we can.
How about the following patch instead? I installed it in gnulib and
coreutils (though I suspect it may not be the last word, with all
these screwy compilers to test....).
2005-09-23 Paul Eggert <[EMAIL PROTECTED]>
* verify.h (GL_CONCAT0, GL_CONCAT): Remove.
(verify): Don't use the __LINE__ trick, as it doesn't work in general.
Instead, declare a function that returns a pointer to an array,
and use verify_type__ to declare the size of the array.
Problem and germ of a solution reported by Bruno Haible.
--- verify.h 22 Sep 2005 22:56:29 -0000 1.1
+++ verify.h 23 Sep 2005 17:52:49 -0000 1.3
@@ -21,34 +21,23 @@
#ifndef VERIFY_H
# define VERIFY_H 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 if 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. */
+/* Each of these macros verifies that its argument R is a nonzero
+ constant expression. To be portable, R's type must be integer (or
+ boolean). Unlike assert, there is no run-time overhead. */
+
+/* A type that is valid if and only if R is a nonzero constant expression.
+ The symbols verify_type__ and verify_error_if_negative_size__ 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. */
+/* Verify requirement R at compile-time, as a declaration. */
# define verify(R) \
- extern verify_type__ (R) GL_CONCAT (verify_function_, __LINE__) (void)
+ extern int (* verify_function__ (void)) [sizeof (verify_type__ (R))]
/* 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. */
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