QPID-4531 : older GCC libs have error on negative-zero cast.

This is a real fix, a replacement for r1431435, which was
written by a crazy person.


git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1431548 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 13 insertions, 7 deletions

diff --git a/qpid/cpp/src/qpid/types/Variant.cpp b/qpid/cpp/src/qpid/types/Variant.cpp
index 139ddc7ab4..8c9837e765 100644
--- a/qpid/cpp/src/qpid/types/Variant.cpp
+++ b/qpid/cpp/src/qpid/types/Variant.cpp
@@ -110,22 +110,28 @@ class VariantImpl
     } value;
     std::string encoding;//optional encoding for variable length data
 
-    template<class T> T convertFromString() const
+  template<class T> T convertFromString() const
     {
         const std::string& s = *value.string;
 
         try {
-            T r = boost::lexical_cast<T>(s);
-            //lexical_cast won't fail if string is a negative number and T is unsigned
-            //So check that and allow special case of negative zero
-            //else its a non-zero negative number so throw exception at end of function
-            if (std::numeric_limits<T>::is_signed || s.find('-') != 0 || r == 0) {
-                return r;
+            // Extra shenanigans to work around negative zero
+            // conversion error in older GCC libs.
+            if ( s[0] != '-' ) {
+                return boost::lexical_cast<T>(s);
+            } else {
+                T r = boost::lexical_cast<T>(s.substr(1));
+                if (std::numeric_limits<T>::is_signed) {
+                    return -r;                    
+                } else {
+                    if (r==0) return 0;
+                }
             }
         } catch(const boost::bad_lexical_cast&) {
         }
         throw InvalidConversion(QPID_MSG("Cannot convert " << s));
     }
+
 };