[PATCH/RFC] autoconf: Add test for OLD_ICONV

[Jakub Narebski <jnareb@gmail.com>]

Update configure.ac (and config.mak.in) to keep up with git
development by adding [compile] test whether your library has
an old iconv(), where the second (input buffer pointer) parameter
is declared with type (const char **) (OLD_ICONV).

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
This patch needs checking if it correctly sets OLD_ICONV
when needed.  I have checked only that it is not set when
with new iconv() declaration.  Could people using Cygwin
(and other with OLD_ICONV: Darwin) test it?

I should probably used AC_LANG_PROGRAM like for NO_C99_FORMAT instead
of generating whole programlet^W test program by hand (I hope that for
example I haven't missed some header file which needs to be included);
I have followed example for NO_ICONV / NEEDS_LIBICONV and
NO_DEFLATE_BOUND test.  I'm also not sure if I have put this test in
the correct autoconf section, but that is probably matter of taste.

P.S. Is there any convention on where to use YesPlease, and where
UnfortunatelyYes when setting Makefile build configuration variables?

 config.mak.in |    1 +
 configure.ac  |   21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/config.mak.in b/config.mak.in
index 11d256e..7d5df9b 100644
--- a/config.mak.in
+++ b/config.mak.in
@@ -41,4 +41,5 @@ NO_STRTOUMAX=@NO_STRTOUMAX@
 NO_SETENV=@NO_SETENV@
 NO_MKDTEMP=@NO_MKDTEMP@
 NO_ICONV=@NO_ICONV@
+OLD_ICONV=@OLD_ICONV@
 NO_DEFLATE_BOUND=@NO_DEFLATE_BOUND@
diff --git a/configure.ac b/configure.ac
index 5f8a15b..5d2936e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -212,6 +212,27 @@ test -n "$NEEDS_SOCKET" && LIBS="$LIBS -lsocket"
 
 
 ## Checks for header files.
+AC_MSG_NOTICE([CHECKS for header files])
+#
+# Define OLD_ICONV if your library has an old iconv(), where the second
+# (input buffer pointer) parameter is declared with type (const char **).
+AC_DEFUN([OLDICONVTEST_SRC], [[
+#include <iconv.h>
+
+int main(void)
+{
+	iconv_t cd;
+	char *ibp, *obp;
+	size_t insz, outsz;
+	iconv(cd, &ibp, &insz, &obp, &outsz);
+}
+]])
+AC_MSG_CHECKING([for old iconv()])
+AC_COMPILE_IFELSE(OLDICONVTEST_SRC,
+	[AC_MSG_RESULT([no])],
+	[AC_MSG_RESULT([yes])
+	OLD_ICONV=YesPlease])
+AC_SUBST(OLD_ICONV)
 
 
 ## Checks for typedefs, structures, and compiler characteristics.
-- 
1.5.3.6