** Backward incompatibilities
+*** AC_CHECK_FUNC and similar macros now use function prototypes.
+ AC_CHECK_FUNC and and similar macros now use C declarations with
+ function prototypes, a feature introduced in C89. The new approach
+ should work better with C23, which removed the non-prototyped K&R
+ style that AC_CHECK_FUNC previously used. However, this change
+ means Autoconf no longer supports pre-1989 C compilers, as they do
+ not support function prototypes.
+
*** Autoconf now requires perl 5.10 (2007) or later.
Generated 'configure' scripts continue to run without perl.