Ticket #5598: json_parser_write.hpp.2.diff

boost/property_tree/detail/json_parser_write.hpp

@@ -19 +19 @@
 
 namespace boost { namespace property_tree { namespace json_parser
 {
+    /* 
+     * Add specialized checks for the case where the character 
+     * class is char or unsigned char. The specialized check avoids 
+     * comparing to <= 0xFF which triggers a GCC warning about the 
+     * fact that the check is always true. 
+     *
+     * See https://svn.boost.org/trac/boost/ticket/5598 
+     */ 
+    namespace detail { 
+      template <class Ch> 
+      bool check_is_ascii(const Ch c) 
+      { 
+        return (c == 0x20 || c == 0x21 || (c >= 0x23 && c <= 0x2E) || 
+               (c >= 0x30 && c <= 0x5B) || (c >= 0x5D && c <= 0xFF)); 
+      } 
+
+      template <> 
+      bool check_is_ascii(const char c) 
+      { 
+        return (c == 0x20 || c == 0x21 || (c >= 0x23 && c <= 0x2E) || 
+               (c >= 0x30 && c <= 0x5B) || c >= 0x5D); 
+      } 
+
+      template <> 
+      bool check_is_ascii(const unsigned char c) 
+      { 
+        return (c == 0x20 || c == 0x21 || (c >= 0x23 && c <= 0x2E) || 
+               (c >= 0x30 && c <= 0x5B) || c >= 0x5D); 
+      } 
+    }  
 
     // Create necessary escape sequences from illegal characters
     template<class Ch>
@@ -32 +62 @@
             // This assumes an ASCII superset. But so does everything in PTree.
             // We escape everything outside ASCII, because this code can't
             // handle high unicode characters.
-            if (*b == 0x20 || *b == 0x21 || (*b >= 0x23 && *b <= 0x2E) ||
-                (*b >= 0x30 && *b <= 0x5B) || (*b >= 0x5D && *b <= 0xFF))
+            if (detail::check_is_ascii(*b))                
                 result += *b;
             else if (*b == Ch('\b')) result += Ch('\\'), result += Ch('b');
             else if (*b == Ch('\f')) result += Ch('\\'), result += Ch('f');