I have a case where I am trying to write an autoconf m4 function to
allow me to use several different APIs the same. In at least one case,
that requires me to define a macro, not just a simple
#define FOO 1
In trying to do that, I found that AC_DEFINE doesn't like parens no
matter how many "[]"'s you put them in. That lead me to finding the
definition of AC_DEFINE and AC_DEFINE_UNQUOTED (mysteriously
identical?), which are listed below.
So the questions are:
1) how would I make an m4 function similar to this
that would handle macros? e.g.
#define theirFunc(a) myFunc(a,0)
2) how is it that AC_DEFINE_UNQUOTED does what its name says?
3) Can someone help me understand the magic lines here?
I don't understand the "[@%:@define]" string, but I assume that it
magically gets transformed into "#define". I also do not understand
the trailing "1" on the m4_if.
---/usr/share/autoconf/autoconf/general.m4---
m4_define([AC_DEFINE],
[AC_DEFINE_TRACE([$1])dnl
m4_ifval([$3], [AH_TEMPLATE([$1], [$3])])dnl
cat >>confdefs.h <<\_ACEOF
[@%:@define] $1 m4_if($#, 2, [$2], $#, 3, [$2], 1)
_ACEOF
])
# AC_DEFINE_UNQUOTED(VARIABLE, [VALUE], [DESCRIPTION])
# ----------------------------------------------------
# Similar, but perform shell substitutions $ ` \ once on VALUE.
m4_define([AC_DEFINE_UNQUOTED],
[AC_DEFINE_TRACE([$1])dnl
m4_ifval([$3], [AH_TEMPLATE([$1], [$3])])dnl
cat >>confdefs.h <<_ACEOF
[@%:@define] $1 m4_if($#, 2, [$2], $#, 3, [$2], 1)
_ACEOF
])
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