Avoid conversion warning in O[U]String[Buffer] constructors

Signed-off-by: Stephan Bergmann <sbergman@redhat.com>, modifying the patch to
carefully keep the undefined behavior in the already existing additions that may
potentially overflow, instead of making the static_cast<sal_Int32> introduction
look like end - pData->buffer will be guaranteed to fit into sal_Int32 (which it
is not).

Change-Id: Id2fb64dc4585dae34257be6968a8905254a3b42d

include/rtl/strbuf.hxx

@@ -211,7 +211,7 @@ public:
         pData = rtl_string_alloc( nCapacity );
         char* end = c.addData( pData->buffer );
         *end = '\0';
-        pData->length = end - pData->buffer;
+        pData->length = l;
     }
 #endif
 
@@ -486,13 +486,14 @@ public:
     template< typename T1, typename T2 >
     OStringBuffer& append( const OStringConcat< T1, T2 >& c )
     {
-        const int l = c.length();
+        sal_Int32 l = c.length();
         if( l == 0 )
             return *this;
-        rtl_stringbuffer_ensureCapacity( &pData, &nCapacity, pData->length + l );
+        l += pData->length;
+        rtl_stringbuffer_ensureCapacity( &pData, &nCapacity, l );
         char* end = c.addData( pData->buffer + pData->length );
         *end = '\0';
-        pData->length = end - pData->buffer;
+        pData->length = l;
         return *this;
     }
 #endif

include/rtl/string.hxx

@@ -244,7 +244,7 @@ public:
         if (l != 0)
         {
             char* end = c.addData( pData->buffer );
-            pData->length = end - pData->buffer;
+            pData->length = l;
             *end = '\0';
         }
     }
@@ -305,13 +305,14 @@ public:
     template< typename T1, typename T2 >
     OString& operator+=( const OStringConcat< T1, T2 >& c )
     {
-        const int l = c.length();
+        sal_Int32 l = c.length();
         if( l == 0 )
             return *this;
-        rtl_string_ensureCapacity( &pData, pData->length + l );
+        l += pData->length;
+        rtl_string_ensureCapacity( &pData, l );
         char* end = c.addData( pData->buffer + pData->length );
         *end = '\0';
-        pData->length = end - pData->buffer;
+        pData->length = l;
         return *this;
     }
 #endif

include/rtl/ustrbuf.hxx

@@ -181,7 +181,7 @@ public:
         pData = rtl_uString_alloc( nCapacity );
         sal_Unicode* end = c.addData( pData->buffer );
         *end = '\0';
-        pData->length = end - pData->buffer;
+        pData->length = l;
         // TODO realloc in case pData->>length is noticeably smaller than l ?
     }
 #endif
@@ -484,13 +484,14 @@ public:
     template< typename T1, typename T2 >
     OUStringBuffer& append( const OUStringConcat< T1, T2 >& c )
     {
-        const int l = c.length();
+        sal_Int32 l = c.length();
         if( l == 0 )
             return *this;
-        rtl_uStringbuffer_ensureCapacity( &pData, &nCapacity, pData->length + l );
+        l += pData->length;
+        rtl_uStringbuffer_ensureCapacity( &pData, &nCapacity, l );
         sal_Unicode* end = c.addData( pData->buffer + pData->length );
         *end = '\0';
-        pData->length = end - pData->buffer;
+        pData->length = l;
         return *this;
     }
 #endif

include/rtl/ustring.hxx

@@ -349,7 +349,7 @@ public:
         if (l != 0)
         {
             sal_Unicode* end = c.addData( pData->buffer );
-            pData->length = end - pData->buffer;
+            pData->length = l;
             *end = '\0';
             // TODO realloc in case pData->length is noticeably smaller than l?
         }
@@ -445,13 +445,14 @@ public:
     template< typename T1, typename T2 >
     OUString& operator+=( const OUStringConcat< T1, T2 >& c )
     {
-        const int l = c.length();
+        sal_Int32 l = c.length();
         if( l == 0 )
             return *this;
-        rtl_uString_ensureCapacity( &pData, pData->length + l );
+        l += pData->length;
+        rtl_uString_ensureCapacity( &pData, l );
         sal_Unicode* end = c.addData( pData->buffer + pData->length );
         *end = '\0';
-        pData->length = end - pData->buffer;
+        pData->length = l;
         return *this;
     }
 #endif