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Date: Sat, 30 Nov 2002 20:56:00 -0000
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From: Paolo Carlini <pcarlini@unitus.it>
Subject: Re: libstdc++/8636: ostringstreams lose their data
Reply-To: Paolo Carlini <pcarlini@unitus.it>
X-SW-Source: 2002-11/txt/msg01212.txt.bz2
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The following reply was made to PR libstdc++/8636; it has been noted by GNATS.

From: Paolo Carlini <pcarlini@unitus.it>
To: gcc-gnats@gcc.gnu.org,  nobody@gcc.gnu.org
Cc:  
Subject: Re: libstdc++/8636: ostringstreams lose their data
Date: Thu, 21 Nov 2002 13:15:49 +0100

 Hello again,
 I think I found the reason for this, it's not a bug.
 
 If 'oss' is an ostringstream, then calling
 
    x = oss.str().c_str();
 
 is a bad idea, because oss.str() returns a copy of the contents of oss
 by value, i.e. a temporary value that is free'd right after this
 statement.  Therefore x is invalid, pointing to a free'd memory region.
 
 --> oss.str().c_str() will always return a pointer to a temporary
      value.
      For example, strcpy(dest, oss.str().c_str()) would work, but
      not   x=oss.str().c_str(); strcpy(dest,x);
 
 I believe this is ok with the standard.
 Sorry, my fault.
 
 Regards,
 Michael
 
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8636