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From: René Bürgel (r.buergel_at_[hidden])
Date: 2007-03-05 11:05:51


There is a bug in boost::format. It occurs, when format::parse is
called multiple times.
If there is a prefix before the first argument (%1%), it is prepended to
the new prefix.

I filed a minimal testcase to reproduce it. It works for Boost 1.33.1
and the CVS-Version.

#include <boost/format.hpp>
#include <iostream>

int main()
       boost::format Formatter;
       std::string Format1 = "sec = %1%";
       std::string Format2 = "min = %1%";

       Formatter.parse( Format1 );
       Formatter.parse( Format2 );

       Formatter % 3u; //just to write something

       std::cout << Formatter.str() << std::endl; //it prints "sec =
min = 3" instead of "min = 3"

A Patch against Boost 1.33.1 is here:

--- parsing.hpp 2006-10-20 08:36:42.000000000 +0100
+++ parsing2.hpp 2007-03-05 14:49:10.000000000 +0100
@@ -413,6 +413,7 @@
        // A: find upper_bound on num_items and allocates arrays
        int num_items = io::detail::upper_bound_from_fstring(buf,
arg_mark, fac, exceptions());
+ prefix_.resize( 0 );

        // B: Now the real parsing of the format string :

René Bürgel

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