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author | Zack Weinberg <zackw@panix.com> | 2020-11-26 10:19:19 -0500 |
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committer | Zack Weinberg <zackw@panix.com> | 2020-11-30 11:45:28 -0500 |
commit | f44695c56b65e29829da43b594c31c59de5766a6 (patch) | |
tree | 9b75b6e6957800a6ad2a59cf3c9bf28bda9b1d9d /NEWS | |
parent | b8c150bd0d8a3979ec1060f4c0a498e6bd1cd717 (diff) | |
download | autoconf-f44695c56b65e29829da43b594c31c59de5766a6.tar.gz |
Add more release notes about compatibility problems.
See https://savannah.gnu.org/support/?110382 and
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97998 for background.
Diffstat (limited to 'NEWS')
-rw-r--r-- | NEWS | 32 |
1 files changed, 32 insertions, 0 deletions
@@ -81,6 +81,38 @@ GNU Autoconf NEWS - User visible changes. how to write configure scripts for C++ programs, and for programs with code in more than one language. +*** Running configure tests with warnings promoted to errors is not supported. + + For instance, setting ‘CC="gcc -Werror"’ on the configure command + line, or adding -Werror to CFLAGS early in the configure script when + the compiler recognizes this option, is very likely to cause + subsequent tests to fail. + + This has never been guaranteed to work; the code generated by + AC_CHECK_FUNC, for instance, is incorrect by a strict reading of the + original 1989 C standard, and has been ever since that macro was + introduced. Problems are more likely with newer, pickier compilers. + + To enable compiler warnings and/or warnings-as-errors mode for your + own code, we currently recommend a dedicated Makefile variable + (e.g. ‘WARN_CFLAGS’) that is set by AC_SUBST when appropriate. + The Gnulib ‘warnings’ and ‘manywarnings’ modules can help with this. + We plan to add core support for probing for useful sets of compiler + warnings in a future release. + +*** Including confdefs.h manually may cause test failures. + + This has never been necessary; confdefs.h is automatically included + at the beginning of all test programs (by AC_LANG_SOURCE). Because + of the way confdefs.h is generated and used, it is not practical to + give it a multiple inclusion guard. Therefore, if you include it + yourself, all of its definitions will be scanned twice. + + Historically this has not been a problem, because confdefs.h only + makes macro definitions, and the C standard allows redefinitions + of macros as long as they’re exactly the same, but newer, pickier + compilers may complain anyway (see for instance GCC bug 97998). + *** Older versions of automake and aclocal (< 1.8) are no longer supported. *** AC_CONFIG_SUBDIRS no longer directly supports Cygnus configure. |