BuildSystem: Fix misdetection of gethostbyname_r() on NetBSD

Fix the configure script not to detect the presence of gethostbyname_r()
on NetBSD incorrectly.  NetBSD includes it as an internal libc symbol
that is not exposed in system headers and that is incompatible with
other implementations.  In order to avoid misdetecting it, perform
the symbol check only if the declaration is found in the public header
first.

ASTERISK-29817

Change-Id: Iafa359b09908251bcd299ff54be003ea129b9eda

configure

@@ -2877,6 +2877,52 @@ $as_echo "$ac_res" >&6; }
 
 } # ac_fn_c_check_member
 
+# ac_fn_c_check_decl LINENO SYMBOL VAR INCLUDES
+# ---------------------------------------------
+# Tests whether SYMBOL is declared in INCLUDES, setting cache variable VAR
+# accordingly.
+ac_fn_c_check_decl ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  as_decl_name=`echo $2|sed 's/ *(.*//'`
+  as_decl_use=`echo $2|sed -e 's/(/((/' -e 's/)/) 0&/' -e 's/,/) 0& (/g'`
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $as_decl_name is declared" >&5
+$as_echo_n "checking whether $as_decl_name is declared... " >&6; }
+if eval \${$3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$4
+int
+main ()
+{
+#ifndef $as_decl_name
+#ifdef __cplusplus
+  (void) $as_decl_use;
+#else
+  (void) $as_decl_name;
+#endif
+#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  eval "$3=yes"
+else
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_c_check_decl
+
 # ac_fn_c_compute_int LINENO EXPR VAR INCLUDES
 # --------------------------------------------
 # Tries to find the compile-time value of EXPR in a program that includes
@@ -17339,6 +17385,28 @@ fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
 
+# NetBSD libc ships with an internal-only incompatible symbol gethostbyname_r
+ac_fn_c_check_decl "$LINENO" "gethostbyname_r" "ac_cv_have_decl_gethostbyname_r" "#include <stdlib.h>
+         #include <netdb.h>
+
+"
+if test "x$ac_cv_have_decl_gethostbyname_r" = xyes; then :
+  ac_have_decl=1
+else
+  ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL_GETHOSTBYNAME_R $ac_have_decl
+_ACEOF
+if test $ac_have_decl = 1; then :
+  have_gethostbyname_r_public_declaration=yes
+else
+  have_gethostbyname_r_public_declaration=no
+fi
+
+
+if test "x$have_gethostbyname_r_public_declaration" = "xyes"; then
         # some systems already have gethostbyname_r so we don't need to build ours in main/utils.c
         { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing gethostbyname_r" >&5
 $as_echo_n "checking for library containing gethostbyname_r... " >&6; }
@@ -17452,6 +17520,7 @@ $as_echo "no" >&6; }
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
+fi
 
 ac_fn_c_check_header_mongrel "$LINENO" "byteswap.h" "ac_cv_header_byteswap_h" "$ac_includes_default"
 if test "x$ac_cv_header_byteswap_h" = xyes; then :

configure.ac

@@ -945,6 +945,15 @@ AC_LINK_IFELSE(
 		AC_MSG_RESULT(no)
 )
 
+# NetBSD libc ships with an internal-only incompatible symbol gethostbyname_r
+AC_CHECK_DECLS([gethostbyname_r],
+        [have_gethostbyname_r_public_declaration=yes],
+        [have_gethostbyname_r_public_declaration=no],
+        [#include <stdlib.h>
+         #include <netdb.h>]
+)
+
+if test "x$have_gethostbyname_r_public_declaration" = "xyes"; then
         # some systems already have gethostbyname_r so we don't need to build ours in main/utils.c
         AC_SEARCH_LIBS(gethostbyname_r, [socket nsl])
 
@@ -967,6 +976,7 @@ AC_LINK_IFELSE(
                 AC_DEFINE([HAVE_GETHOSTBYNAME_R_5], 1, [Define to 1 if your system has gethostbyname_r with 5 arguments.]),
                 AC_MSG_RESULT(no)
         )
+fi
 
 AC_CHECK_HEADER([byteswap.h], [AC_DEFINE_UNQUOTED([HAVE_BYTESWAP_H], 1, [Define to 1 if byteswap.h macros are available.])])