[ loki-lib-Bugs-1515809 ] loki-lib 0.1.5 SafeFormat.h write bug

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Bugs item #1515809, was opened at 2006-07-02 12:53
Message generated for change (Comment added) made by syntheticpp
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Category: None
Group: None
>Status: Closed
>Resolution: Accepted
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
>Assigned to: Peter Kuemmel (syntheticpp)
Summary: loki-lib 0.1.5 SafeFormat.h write bug

Initial Comment:
I'm very sorry that my English is poor, but I really 
want to explain it exactly.

In the template write function which is annotated 
as "Write to a fixed-size buffer", there is a bug.
the snippets codes is as follow:
if (from + s.second > to) throw std::overflow_error
("");

I think it should be like this:
if (s.second < to - from) throw std::overflow_error
("");

My demo codes is as follow:

#include <utility>
#include <string>
#include <cassert>

template <class Char>
void write(std::pair<Char*, std::size_t>& s, const 
Char* from, const Char* to) {
	assert(from <= to);
	if (from + s.second > to) throw 
std::overflow_error("");
	s.first = std::copy(from, to, s.first);
	s.second -= to - from;
}

int main()
{
	char ch[20];
	std::size_t n = 20;

	std::pair<char*, std::size_t> p( ch, n );

	std::string s( "1234567890" );
	write( p, &*s.begin(), &*(--s.end()) );

	return 0;
}


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>Comment By: Peter Kuemmel (syntheticpp)
Date: 2006-07-03 12:02

Message:
Logged In: YES 
user_id=1159765

I've no problem understanding your English,
I'm also not a nativ speaker.

And aes, you are right, seems this is a bug.

The logic should be:
Throw an exception when 'to' is beyond 
'from' plus the size of the buffer, because
then the string does not fit into the buffer.

I've fixed it.

Many thanks,
Peter
Index: SafeFormat.h
===================================================================
RCS file: /cvsroot/loki-lib/loki/include/loki/SafeFormat.h,v
retrieving revision 1.26
retrieving revision 1.27
diff -u -d -r1.26 -r1.27
--- SafeFormat.h	28 Jun 2006 08:04:21 -0000	1.26
+++ SafeFormat.h	3 Jul 2006 09:55:19 -0000	1.27
@@ -61,8 +61,11 @@
     template <class Char>
     void write(std::pair<Char*, std::size_t>& s, const
Char* from, const Char* to) {
         assert(from <= to);
-        if (from + s.second > to) throw
std::overflow_error("");
-        s.first = copy(from, to, s.first);
+        if(from + s.second < to)
+            throw std::overflow_error("");
+        // s.first: position one past the final copied element 
+        s.first = std::copy(from, to, s.first);
+        // remaining buffer size
         s.second -= to - from;
     }
 
@@ -573,6 +576,9 @@
 #endif //SAFEFORMAT_H_
 
 // $Log$
+// Revision 1.27  2006/07/03 09:55:19  syntheticpp
+// fix wrong buffer size check
+//
 // Revision 1.26  2006/06/28 08:04:21  syntheticpp
 // use standard conforming naming, SUN's compiler needs it
 //

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