AC_FUNC_ALLOCA

removed because of limited usefulness

This macro is obsolete; it does nothing.

If the C compiler supports a working long double type with more range or precision than the double type, define HAVE_LONG_DOUBLE.

You should use AC_TYPE_LONG_DOUBLE or AC_TYPE_LONG_DOUBLE_WIDER instead. See Particular Types.

Determine the system type and set output variables to the names of the canonical system types. See Canonicalizing, for details about the variables this macro sets.

The user is encouraged to use either AC_CANONICAL_BUILD, or AC_CANONICAL_HOST, or AC_CANONICAL_TARGET, depending on the needs. Using AC_CANONICAL_TARGET is enough to run the two other macros.

AC_C_CHAR_UNSIGNED

Autoconf, up to 2.13, used to provide this version of AC_CHECK_TYPE, deprecated because of its flaws. First, although it is a member of the CHECK clan, it does more than just checking. Secondly, missing types are defined using #define, not typedef, and this can lead to problems in the case of pointer types.

This use of AC_CHECK_TYPE is obsolete and discouraged; see Generic Types, for the description of the current macro.

If the type type is not defined, define it to be the C (or C++) builtin type default, e.g., ‘short int’ or ‘unsigned int’.

This macro is equivalent to:

          AC_CHECK_TYPE([type], [],
            [AC_DEFINE_UNQUOTED([type], [default],
               [Define to `default'
                if <sys/types.h> does not define.])])
     

In order to keep backward compatibility, the two versions of AC_CHECK_TYPE are implemented, selected by a simple heuristics:

1. If there are three or four arguments, the modern version is used.
2. If the second argument appears to be a C or C++ type, then the obsolete version is used. This happens if the argument is a C or C++ builtin type or a C identifier ending in ‘_t’, optionally followed by one of ‘[(* ’ and then by a string of zero or more characters taken from the set ‘[]()* _a-zA-Z0-9’.
3. If the second argument is spelled with the alphabet of valid C and C++ types, the user is warned and the modern version is used.
4. Otherwise, the modern version is used.

You are encouraged either to use a valid builtin type, or to use the equivalent modern code (see above), or better yet, to use AC_CHECK_TYPES together with

          #if !HAVE_LOFF_T
          typedef loff_t off_t;
          #endif
     

Same as ‘AC_MSG_NOTICE([checking feature-description...]’.

This is an obsolete version of AC_TRY_COMPILE itself replaced by AC_COMPILE_IFELSE (see Running the Compiler), with the addition that it prints ‘checking for echo-text’ to the standard output first, if echo-text is non-empty. Use AC_MSG_CHECKING and AC_MSG_RESULT instead to print messages (see Printing Messages).

AC_C_CONST

Same as AC_C_CROSS, which is obsolete too, and does nothing :-).

Check for the Cygwin environment in which case the shell variable CYGWIN is set to ‘yes’. Don't use this macro, the dignified means to check the nature of the host is using AC_CANONICAL_HOST. As a matter of fact this macro is defined as:

          AC_REQUIRE([AC_CANONICAL_HOST])[]dnl
          case $host_os in
            *cygwin* ) CYGWIN=yes;;
                   * ) CYGWIN=no;;
          esac
     

Beware that the variable CYGWIN has a special meaning when running Cygwin, and should not be changed. That's yet another reason not to use this macro.

Same as:

          AC_CHECK_DECLS([sys_siglist], [], [],
          [#include <signal.h>
          /* NetBSD declares sys_siglist in unistd.h.  */
          #if HAVE_UNISTD_H
          # include <unistd.h>
          #endif
          ])
     

Does nothing, now integrated in AC_PROG_LEX.

Like calling AC_FUNC_CLOSEDIR_VOID andAC_HEADER_DIRENT, but defines a different set of C preprocessor macros to indicate which header file is found:

Header	Old Symbol	New Symbol
dirent.h	DIRENT	HAVE_DIRENT_H
sys/ndir.h	SYSNDIR	HAVE_SYS_NDIR_H
sys/dir.h	SYSDIR	HAVE_SYS_DIR_H
ndir.h	NDIR	HAVE_NDIR_H

If on DYNIX/ptx, add -lseq to output variable LIBS. This macro used to be defined as

          AC_CHECK_LIB([seq], [getmntent], [LIBS="-lseq $LIBS"])
     

now it is just AC_FUNC_GETMNTENT.

Defined the output variable EXEEXT based on the output of the compiler, which is now done automatically. Typically set to empty string if Posix and ‘.exe’ if a DOS variant.

Similar to AC_CYGWIN but checks for the EMX environment on OS/2 and sets EMXOS2.

AC_MSG_ERROR

AC_PATH_X

AC_PATH_XTRA

m4_foreach_w

AC_CHECK_FUNC

If wait3 is found and fills in the contents of its third argument (a ‘struct rusage *’), which HP-UX does not do, define HAVE_WAIT3.

These days portable programs should use waitpid, not wait3, as wait3 has been removed from Posix.

AC_PROG_GCC_TRADITIONAL

AC_TYPE_GETGROUPS

AC_FUNC_GETLOADAVG

AC_CHECK_FUNCS

AC_CHECK_HEADERS

This macro is equivalent to calling AC_CHECK_LIB with a function argument of main. In addition, library can be written as any of ‘foo’, -lfoo, or ‘libfoo.a’. In all of those cases, the compiler is passed -lfoo. However, library cannot be a shell variable; it must be a literal name.

AC_SYS_INTERPRETER (different calling convention)

AC_CHECK_HEADER

AC_EGREP_HEADER

AS_HELP_STRING

Formerly AC_INIT used to have a single argument, and was equivalent to:

          AC_INIT
          AC_CONFIG_SRCDIR(unique-file-in-source-dir)
     

AC_C_INLINE

If the C type int is 16 bits wide, define INT_16_BITS. Use ‘AC_CHECK_SIZEOF(int)’ instead.

If on irix (Silicon Graphics Unix), add -lsun to output LIBS. If you were using it to get getmntent, use AC_FUNC_GETMNTENT instead. If you used it for the NIS versions of the password and group functions, use ‘AC_CHECK_LIB(sun, getpwnam)’. Up to Autoconf 2.13, it used to be

          AC_CHECK_LIB([sun], [getmntent], [LIBS="-lsun $LIBS"])
     

now it is defined as

          AC_FUNC_GETMNTENT
          AC_CHECK_LIB([sun], [getpwnam])
     

Same as ‘AC_LANG([C])’.

Same as ‘AC_LANG([C++])’.

Same as ‘AC_LANG([Fortran 77])’.

Select the language that is saved on the top of the stack, as set by AC_LANG_SAVE, remove it from the stack, and call AC_LANG(language).

Remember the current language (as set by AC_LANG) on a stack. The current language does not change. AC_LANG_PUSH is preferred.

This is an obsolete version of AC_CONFIG_LINKS. An updated version of:

          AC_LINK_FILES(config/$machine.h config/$obj_format.h,
                        host.h            object.h)
     

is:

          AC_CONFIG_LINKS([host.h:config/$machine.h
                          object.h:config/$obj_format.h])
     

AC_PROG_LN_S

Define LONG_64_BITS if the C type long int is 64 bits wide. Use the generic macro ‘AC_CHECK_SIZEOF([long int])’ instead.

If the C compiler supports a working long double type with more range or precision than the double type, define HAVE_LONG_DOUBLE.

You should use AC_TYPE_LONG_DOUBLE or AC_TYPE_LONG_DOUBLE_WIDER instead. See Particular Types.

AC_SYS_LONG_FILE_NAMES

AC_HEADER_MAJOR

Used to define NEED_MEMORY_H if the mem functions were defined in memory.h. Today it is equivalent to ‘AC_CHECK_HEADERS([memory.h])’. Adjust your code to depend upon HAVE_MEMORY_H, not NEED_MEMORY_H; see Standard Symbols.

Similar to AC_CYGWIN but checks for the MinGW compiler environment and sets MINGW32.

AC_PROG_CC_C_O

AC_FUNC_MMAP

AC_TYPE_MODE_T

Defined the output variable OBJEXT based on the output of the compiler, after .c files have been excluded. Typically set to ‘o’ if Posix, ‘obj’ if a DOS variant. Now the compiler checking macros handle this automatically.

Make M4 print a message to the standard error output warning that this-macro-name is obsolete, and giving the file and line number where it was called. this-macro-name should be the name of the macro that is calling AC_OBSOLETE. If suggestion is given, it is printed at the end of the warning message; for example, it can be a suggestion for what to use instead of this-macro-name.

For instance

          AC_OBSOLETE([$0], [; use AC_CHECK_HEADERS(unistd.h) instead])dnl
     

You are encouraged to use AU_DEFUN instead, since it gives better services to the user.

AC_TYPE_OFF_T

The use of AC_OUTPUT with argument is deprecated. This obsoleted interface is equivalent to:

          AC_CONFIG_FILES(file...)
          AC_CONFIG_COMMANDS([default],
                             extra-cmds, init-cmds)
          AC_OUTPUT
     

Specify additional shell commands to run at the end of config.status, and shell commands to initialize any variables from configure. This macro may be called multiple times. It is obsolete, replaced by AC_CONFIG_COMMANDS.

Here is an unrealistic example:

          fubar=27
          AC_OUTPUT_COMMANDS([echo this is extra $fubar, and so on.],
                             [fubar=$fubar])
          AC_OUTPUT_COMMANDS([echo this is another, extra, bit],
                             [echo init bit])
     

Aside from the fact that AC_CONFIG_COMMANDS requires an additional key, an important difference is that AC_OUTPUT_COMMANDS is quoting its arguments twice, unlike AC_CONFIG_COMMANDS. This means that AC_CONFIG_COMMANDS can safely be given macro calls as arguments:

          AC_CONFIG_COMMANDS(foo, [my_FOO()])
     

Conversely, where one level of quoting was enough for literal strings with AC_OUTPUT_COMMANDS, you need two with AC_CONFIG_COMMANDS. The following lines are equivalent:

          AC_OUTPUT_COMMANDS([echo "Square brackets: []"])
          AC_CONFIG_COMMANDS([default], [[echo "Square brackets: []"]])
     

AC_TYPE_PID_T

AC_PREFIX_PROGRAM

AC_CHECK_PROGS

AC_PATH_PROGS

AC_CHECK_PROG

AC_EGREP_CPP

AC_PATH_PROG

removed because of limited usefulness

AC_SYS_RESTARTABLE_SYSCALLS

AC_TYPE_SIGNAL

removed because of limited usefulness

If on SCO Unix, add -lintl to output variable LIBS. This macro used to do this:

          AC_CHECK_LIB([intl], [strftime], [LIBS="-lintl $LIBS"])
     

Now it just calls AC_FUNC_STRFTIME instead.

AC_FUNC_SETVBUF_REVERSED

AC_PROG_MAKE_SET

AC_CHECK_SIZEOF

AC_TYPE_SIZE_T

AC_HEADER_STAT

AC_HEADER_STDC

AC_FUNC_STRCOLL

AC_CHECK_MEMBERS

AC_STRUCT_ST_BLOCKS

AC_CHECK_MEMBERS

If the system automatically restarts a system call that is interrupted by a signal, define HAVE_RESTARTABLE_SYSCALLS. This macro does not check whether system calls are restarted in general—it checks whether a signal handler installed with signal (but not sigaction) causes system calls to be restarted. It does not check whether system calls can be restarted when interrupted by signals that have no handler.

These days portable programs should use sigaction with SA_RESTART if they want restartable system calls. They should not rely on HAVE_RESTARTABLE_SYSCALLS, since nowadays whether a system call is restartable is a dynamic issue, not a configuration-time issue.

AC_DECL_SYS_SIGLIST

AC_TRY_CPP, replaced by AC_PREPROC_IFELSE.

AC_TRY_RUN, replaced by AC_RUN_IFELSE.

AC_STRUCT_TIMEZONE

AC_HEADER_TIME

Same as:

          AC_COMPILE_IFELSE(
            [AC_LANG_PROGRAM([[includes]],
               [[function-body]])],
            [action-if-true],
            [action-if-false])
     

See Running the Compiler.

This macro double quotes both includes and function-body.

For C and C++, includes is any #include statements needed by the code in function-body (includes is ignored if the currently selected language is Fortran or Fortran 77). The compiler and compilation flags are determined by the current language (see Language Choice).

Same as:

          AC_PREPROC_IFELSE(
            [AC_LANG_SOURCE([[input]])],
            [action-if-true],
            [action-if-false])
     

See Running the Preprocessor.

This macro double quotes the input.

Same as:

          AC_LINK_IFELSE(
            [AC_LANG_PROGRAM([[includes]],
               [[function-body]])],
            [action-if-true],
            [action-if-false])
     

See Running the Compiler.

This macro double quotes both includes and function-body.

Depending on the current language (see Language Choice), create a test program to see whether a function whose body consists of function-body can be compiled and linked. If the file compiles and links successfully, run shell commands action-if-found, otherwise run action-if-not-found.

This macro double quotes both includes and function-body.

For C and C++, includes is any #include statements needed by the code in function-body (includes is ignored if the currently selected language is Fortran or Fortran 77). The compiler and compilation flags are determined by the current language (see Language Choice), and in addition LDFLAGS and LIBS are used for linking.

This macro is equivalent to ‘AC_LINK_IFELSE([AC_LANG_CALL([], [function])], [action-if-found], [action-if-not-found])’.

Same as:

          AC_RUN_IFELSE(
            [AC_LANG_SOURCE([[program]])],
            [action-if-true],
            [action-if-false],
            [action-if-cross-compiling])
     

See Runtime.

AC_TYPE_UID_T

Same as ‘AC_CHECK_HEADERS([unistd.h])’.

Define USG if the BSD string functions are defined in strings.h. You should no longer depend upon USG, but on HAVE_STRING_H; see Standard Symbols.

AC_FUNC_UTIME_NULL

If the cache file is inconsistent with the current host, target and build system types, it used to execute cmd or print a default error message. This is now handled by default.

AC_MSG_RESULT.

AC_FUNC_VFORK

AC_FUNC_VPRINTF

AC_FUNC_WAIT3

AC_MSG_WARN

AC_C_BIGENDIAN

This macro used to add -lx to output variable LIBS if on Xenix. Also, if dirent.h is being checked for, added -ldir to LIBS. Now it is merely an alias of AC_HEADER_DIRENT instead, plus some code to detect whether running xenix on which you should not depend:

          AC_MSG_CHECKING([for Xenix])
          AC_EGREP_CPP([yes],
          [#if defined M_XENIX && !defined M_UNIX
            yes
          #endif],
                       [AC_MSG_RESULT([yes]); XENIX=yes],
                       [AC_MSG_RESULT([no]); XENIX=])
     

AC_DECL_YYTEXT