Change check_null_empty_path* to check_null_empty_str* throughout.

* path.cc (path_conv::check): Add signal protection here since retrieving info
about remote shares can take some time.
* path.h (check_null_empty_str_errno): Convert to a function prototype.
* path.cc (check_null_empty_str): Move to miscfuncs.cc.
* miscfuncs.cc (check_null_empty_str_errno): New function.
(__check_null_invalid_struct): Ditto.
(__check_null_invalid_struct_errno): Ditto.
(check_null_empty_str): Change from VirtualQuery to IsBadWritePtr.
* thread.cc (check_valid_pointer): Ditto.
* resource.cc (getrlimit): Use check_null_invalid_struct macro for checking
validity of pointer.
(setrlimit): Ditto.

winsup/cygwin/miscfuncs.cc

@@ -9,6 +9,8 @@ Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
 details. */
 
 #include "winsup.h"
+#include "cygerrno.h"
+#include <sys/errno.h>
 
 /********************** String Helper Functions ************************/
 
@@ -112,3 +114,42 @@ strcasestr (const char *searchee, const char *lookfor)
 
   return NULL;
 }
+
+int __stdcall
+check_null_empty_str (const char *name)
+{
+  if (!name || IsBadStringPtr (name, MAX_PATH))
+    return EFAULT;
+
+  if (!*name)
+    return ENOENT;
+
+  return 0;
+}
+
+int __stdcall
+check_null_empty_str_errno (const char *name)
+{ 
+  int __err; 
+  if ((__err = check_null_empty_str (name))) 
+    set_errno (__err); 
+  return __err; 
+}
+
+int __stdcall
+__check_null_invalid_struct (const void *s, unsigned sz)
+{
+  if (!s || IsBadWritePtr ((void *) s, sz))
+    return EFAULT;
+
+  return 0;
+}
+
+int __stdcall
+__check_null_invalid_struct_errno (const void *s, unsigned sz)
+{ 
+  int __err; 
+  if ((__err = __check_null_invalid_struct (s, sz))) 
+    set_errno (__err); 
+  return __err; 
+}