Improve portability

- Use clearenv() if it exists
- Don't rely on <limits.h> being pulled in by <sys/param.h>

common/os_calls.c

@@ -95,16 +95,11 @@ struct sockaddr_hvs
 #endif
 
 #include "os_calls.h"
+#include "limits.h"
 #include "string_calls.h"
 #include "log.h"
 #include "xrdp_constants.h"
 
-/* for clearenv() */
-#if defined(_WIN32)
-#else
-extern char **environ;
-#endif
-
 #if defined(__linux__)
 #include <linux/unistd.h>
 #endif
@@ -3446,14 +3441,16 @@ g_setpgid(int pid, int pgid)
 void
 g_clearenv(void)
 {
-#if defined(_WIN32)
-#else
-#if defined(BSD)
+#if defined(HAVE_CLEARENV)
+    clearenv();
+#elif defined(_WIN32)
+#elif defined(BSD)
+    extern char **environ;
     environ[0] = 0;
 #else
+    extern char **environ;
     environ = 0;
 #endif
-#endif
 }
 
 /*****************************************************************************/

configure.ac

@@ -211,7 +211,7 @@ AM_COND_IF([DEVEL_DEBUG],
 AC_SEARCH_LIBS([setusercontext], [util])
 
 # Define HAVE_XXXXX macros for some system functions
-AC_CHECK_FUNCS([setusercontext getgrouplist])
+AC_CHECK_FUNCS([setusercontext getgrouplist clearenv])
 
 # The type used by getgrouplist() is the same type used by getgroups()
 AC_TYPE_GETGROUPS