Greetings,
I could use some help/tips/pointers on writing new Autoconf macros
that do the following tasks:
1. An Autoconf macro that defines a preprocessor name with the expanded
value of an existing preprocessor name. For example,
FOO_REDEFINE_MACRO(FOO_CHAR_BIT, CHAR_BIT, [#include <limits.h>])
would define the name FOO_CHAR_BIT with the _expanded_ value of CHAR_BIT
from the <limits.h> header. The purpose of this macro is to redefine a
name without any include dependencies. So simply defining FOO_CHAR_BIT
as CHAR_BIT isn't good enough because FOO_CHAR_BIT would then require
including the <limits.h> header. Similarly, simply defining
FOO_CHAR_BIT
as the value of CHAR_BIT may not work either because CHAR_BIT itself may
be defined in terms of another preprocessor name. The new name must be
defined as the preprocessed token(s) of the existing name -- an integral
constant in this case.
2. An Autoconf macro that checks whether a given type is a built-in
type or not. This macro is similar to AC_CHECK_TYPE except that it
performs action-if-built-in only if the type is a built-in type and
action-if-not-built-in if the type is not defined or not a built-in
type.
(Possibly the same as _AC_TYPE_CHECK_NEW without any includes at all.)
3. An Autoconf macro that defines a preprocessor name with the
fundamental type as an existing type definition. This macro is similar
to the previous macro (and for similar reasons) except that it checks
for a typedef rather than a preprocessor name and defines the new name
with the _fundamental_ type of the existing typedef. For example,
FOO_REDEFINE_TYPE(FOO_INT8_T, int8_t, AC_INCLUDES_DEFAULT)
would define the preprocessor name FOO_INT8_T with the fundamental type
used to define int8_t in the default headers. Note that the existing
type may be defined in terms of an intermediate type. If int8_t is
defined in the default includes as
#include <sys/types.h>
typedef __sys_int8_t int8_t;
and the type __sys_int8_t is defined in <sys/types.h> as
typedef char __sys_int8_t int8_t;
then FOO_INT8_T should be defined as
#define FOO_INT8_T char
so that there are no include dependencies for FOO_INT8_T.
Any help with these is greatly appreciated.
Eric.
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