File: autoconf.info,  Node: Generic Types,  Prev: Types.php">Particular Types,  Up: Types

5.9.2 Generic Type Checks
-------------------------

These macros are used to check for types not covered by the "particular"
test macros.

 -- Macro: AC_CHECK_TYPE (TYPE, [ACTION-IF-FOUND],
          [ACTION-IF-NOT-FOUND], [INCLUDES = AC_INCLUDES_DEFAULT])
     Check whether TYPE is defined.  It may be a compiler builtin type
     or defined by the INCLUDES.  INCLUDES is a series of include
     directives, defaulting to ‘AC_INCLUDES_DEFAULT’ (*note Default
     Includes::), which are used prior to the type under test.

     In C, TYPE must be a type-name, so that the expression ‘sizeof
     (TYPE)’ is valid (but ‘sizeof ((TYPE))’ is not).  The same test is
     applied when compiling for C++, which means that in C++ TYPE should
     be a type-id and should not be an anonymous ‘struct’ or ‘union’.

     This macro caches its result in the ‘ac_cv_type_TYPE’ variable,
     with ‘*’ mapped to ‘p’ and other characters not suitable for a
     variable name mapped to underscores.

 -- Macro: AC_CHECK_TYPES (TYPES, [ACTION-IF-FOUND],
          [ACTION-IF-NOT-FOUND], [INCLUDES = AC_INCLUDES_DEFAULT])
     For each TYPE of the TYPES that is defined, define ‘HAVE_TYPE’ (in
     all capitals).  Each TYPE must follow the rules of ‘AC_CHECK_TYPE’.
     If no INCLUDES are specified, the default includes are used (*note
     Default Includes::).  If ACTION-IF-FOUND is given, it is additional
     shell code to execute when one of the types is found.  If
     ACTION-IF-NOT-FOUND is given, it is executed when one of the types
     is not found.

     This macro uses M4 lists:
          AC_CHECK_TYPES([ptrdiff_t])
          AC_CHECK_TYPES([unsigned long long int, uintmax_t])
          AC_CHECK_TYPES([float_t], [], [], [[#include ]])

   Autoconf, up to 2.13, used to provide to another version of
‘AC_CHECK_TYPE’, broken by design.  In order to keep backward
compatibility, a simple heuristic, quite safe but not totally, is
implemented.  In case of doubt, read the documentation of the former
‘AC_CHECK_TYPE’, see *note Obsolete Macros::.