diff options
Diffstat (limited to 'NEWS')
| -rw-r--r-- | NEWS | 28 |
1 files changed, 17 insertions, 11 deletions
@@ -136,19 +136,25 @@ GNU Autoconf NEWS - User visible changes. *** AC_INCLUDES_DEFAULT assumes an ISO C90 compliant C implementation. - Specifically, it assumes that the ISO C90 headers <stdlib.h> and - <string.h> are available, without checking for them, and does not - include the pre-standard header <memory.h> at all. If the POSIX - header <strings.h> exists, it will be included, without testing - whether it is safe to include both <string.h> and <strings.h> in the + Specifically, it assumes that the ISO C90 header <stddef.h> + is available, without checking for it, and it does not include + the pre-standard header <memory.h> at all. If the POSIX header + <strings.h> exists, it will be included, without first testing + whether both <string.h> and <strings.h> can be included in the same source file. - For compatibility’s sake, the C preprocessor macros STDC_HEADERS, - HAVE_STDLIB_H, and HAVE_STRING_H are defined unconditionally. - These preprocessor macros should be considered obsolescent. - However, cache variables like ac_cv_header_stdlib_h are not set; - this is intentional, so that AC_CHECK_HEADER([stdlib.h]) will still - do a test for the presence of stdlib.h, in case you genuinely need that. + AC_INCLUDES_DEFAULT still checks for the existence of <stdlib.h>, + <string.h>, and <stdio.h>, because these headers may not exist + in a “freestanding environment” (a compilation mode intended for OS + kernels and similar, where most of the features of the C library are + optional). Most programs need not use ‘#ifdef HAVE_STDLIB_H’ etc in + their own code. + + For compatibility’s sake, the C preprocessor macro STDC_HEADERS + will be defined when both <stdlib.h> and <string.h> are available; + however, <stdarg.h> and <float.h> are no longer checked for + (these, like <stddef.h>, are required to exist in a freestanding + environment). New code should not refer to this macro. Future releases of Autoconf may reduce the set of headers checked for by AC_INCLUDES_DEFAULT. |