AC_CHECK_LIB and C++ libraries

[Magnus Fromreide]

Hello.

I have a C++ program and a library written in C++ that I wish to AC_CHECK_LIB
for, when trying that AC_CHECK_LIB fails miserably since the name mangling
hides the function name. It would be nice if the following were true:

a) AC_CHECK_LIB takes a PROLOGUE argument, just like AC_LANG_CALL and
   AC_LANG_PROGRAM does so that includes can be sent along.

b) AC_LANG_CALL(C++) doesn't try to redeclare functions

By changing AC_LANG_CALL(C++) from

# AC_LANG_CALL(C++)(PROLOGUE, FUNCTION)
# -------------------------------------
m4_copy([AC_LANG_CALL(C)], [AC_LANG_CALL(C++)])

to

# AC_LANG_CALL(C++)(PROLOGUE, FUNCTION)
# -------------------------------------
m4_define([AC_LANG_CALL(C++)], [AC_LANG_PROGRAM([$1], [$2 () ;])])

objective b) is done.

Objective a) can be done by adding a sixth parameter to AC_CHECK_LIB and
AC_SEARCH_LIBS that is forwarded to the first parameter of AC_LANG_CALL in both
macros, but I am not certain if this is the best path forward on this issue.

On another note it could be that AC_CHECK_LIB shouldn't use AC_LANG_CALL but
AC_LANG_PROGRAM if there are any parentheses in the functon name - this makes
it possible to link against functions that takes arguments as well even when
name mangling is present.

/MF