autoconf: Add link tests to each AC_CHECK_FUNC() test

Update configure.ac to test libraries for getaddrinfo, strcasestr, memmem,
strlcpy, strtoumax, setenv, unsetenv, and mkdtemp.  The default compilers
on FreeBSD 4.9-SECURITY and FreeBSD 6.2-RELEASE-p4 do not generate warnings
for missing prototypes unless `-Wall' is used. This behavior renders the
results of AC_CHECK_FUNC() void on these platforms. The test AC_SEARCH_LIBS()
verifies a function is valid by linking to symbol within the system libraries.

Since this pattern needs to be repeated for many functions that are
checked with AC_CHECK_FUNC(), we add GIT_CHECK_FUNC() to drive the two
autoconf macros together.

Signed-off-by: David M. Syzdek <david.syzdek@acsalaska.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

configure.ac

@@ -65,7 +65,17 @@ else \
 fi \
 ])# GIT_PARSE_WITH
 
-
+dnl
+dnl GIT_CHECK_FUNC(FUNCTION, IFTRUE, IFFALSE)
+dnl -----------------------------------------
+dnl Similar to AC_CHECK_FUNC, but on systems that do not generate
+dnl warnings for missing prototypes (e.g. FreeBSD when compiling without
+dnl -Wall), it does not work.  By looking for function definition in
+dnl libraries, this problem can be worked around.
+AC_DEFUN([GIT_CHECK_FUNC],[AC_CHECK_FUNC([$1],[
+  AC_SEARCH_LIBS([$1],,
+  [$2],[$3])
+],[$3])])
 ## Site configuration related to programs (before tests)
 ## --with-PACKAGE[=ARG] and --without-PACKAGE
 #
@@ -325,7 +335,7 @@ AC_SUBST(NO_SOCKADDR_STORAGE)
 #
 # Define NO_IPV6 if you lack IPv6 support and getaddrinfo().
 AC_CHECK_TYPE([struct addrinfo],[
- AC_CHECK_FUNC([getaddrinfo],
+ GIT_CHECK_FUNC([getaddrinfo],
   [NO_IPV6=],
   [NO_IPV6=YesPlease])
 ],[NO_IPV6=YesPlease],[
@@ -419,43 +429,43 @@ AC_SUBST(SNPRINTF_RETURNS_BOGUS)
 AC_MSG_NOTICE([CHECKS for library functions])
 #
 # Define NO_STRCASESTR if you don't have strcasestr.
-AC_CHECK_FUNC(strcasestr,
+GIT_CHECK_FUNC(strcasestr,
 [NO_STRCASESTR=],
 [NO_STRCASESTR=YesPlease])
 AC_SUBST(NO_STRCASESTR)
 #
 # Define NO_MEMMEM if you don't have memmem.
-AC_CHECK_FUNC(memmem,
+GIT_CHECK_FUNC(memmem,
 [NO_MEMMEM=],
 [NO_MEMMEM=YesPlease])
 AC_SUBST(NO_MEMMEM)
 #
 # Define NO_STRLCPY if you don't have strlcpy.
-AC_CHECK_FUNC(strlcpy,
+GIT_CHECK_FUNC(strlcpy,
 [NO_STRLCPY=],
 [NO_STRLCPY=YesPlease])
 AC_SUBST(NO_STRLCPY)
 #
 # Define NO_STRTOUMAX if you don't have strtoumax in the C library.
-AC_CHECK_FUNC(strtoumax,
+GIT_CHECK_FUNC(strtoumax,
 [NO_STRTOUMAX=],
 [NO_STRTOUMAX=YesPlease])
 AC_SUBST(NO_STRTOUMAX)
 #
 # Define NO_SETENV if you don't have setenv in the C library.
-AC_CHECK_FUNC(setenv,
+GIT_CHECK_FUNC(setenv,
 [NO_SETENV=],
 [NO_SETENV=YesPlease])
 AC_SUBST(NO_SETENV)
 #
 # Define NO_UNSETENV if you don't have unsetenv in the C library.
-AC_CHECK_FUNC(unsetenv,
+GIT_CHECK_FUNC(unsetenv,
 [NO_UNSETENV=],
 [NO_UNSETENV=YesPlease])
 AC_SUBST(NO_UNSETENV)
 #
 # Define NO_MKDTEMP if you don't have mkdtemp in the C library.
-AC_CHECK_FUNC(mkdtemp,
+GIT_CHECK_FUNC(mkdtemp,
 [NO_MKDTEMP=],
 [NO_MKDTEMP=YesPlease])
 AC_SUBST(NO_MKDTEMP)