15.5.3 Changed Macros

Many of the macros were renamed in Autoconf version 2. You can still use the old names, but the new ones are clearer, and it's easier to find the documentation for them. See section 15.4 Obsolete Macros, for a table showing the new names for the old macros. Use the autoupdate program to convert your `configure.ac' to using the new macro names. See section 15.3 Using autoupdate to Modernize `configure.ac'.

Some macros have been superseded by similar ones that do the job better, but are not call-compatible. If you get warnings about calling obsolete macros while running autoconf, you may safely ignore them, but your configure script will generally work better if you follow the advice it prints about what to replace the obsolete macros with. In particular, the mechanism for reporting the results of tests has changed. If you were using echo or AC_VERBOSE (perhaps via AC_COMPILE_CHECK), your configure script's output will look better if you switch to AC_MSG_CHECKING and AC_MSG_RESULT. See section 7.4 Printing Messages. Those macros work best in conjunction with cache variables. See section 7.3 Caching Results.