[Boost-users] [iostreams] Hang when constructing an xml_iarchive with non-existent source

From: Paul Giaccone (paulg_at_[hidden])
Date: 2006-02-08 07:26:20

I have a function that uses a chain of filters that I am using to read 
encrypted, bzipped data from file.  It is working fine.

However, I have just discovered that if I call my function with a file 
that does not exist, the code hangs in the constructor for xml_iarchive.

Of course, I have since edited my code to trap non-existent files before 
the code gets that far, but I am surprised that:

* is_complete() returns true when the source is a non-existent file
* the constructor for xml_iarchive hangs when it is given a stream that 
has a non-existent file as its source

Is this correct behaviour or a bug?  Of course, it is the programmer's 
responsibility to ensure the source exists, but a hang rather than an 
exception seems suggests to me that something has been overlooked in the 
library.

The (edited) function exhibiting this behaviour is given below.  I am 
using gcc 3.2.3 and Boost 1.33.1.

Paul

void load(const std::string& filename)
{
    //my revised tests "filename" here and bails out if the file does 
not exist

    try
    {
        boost::iostreams::filtering_istream in;
        in.push(boost::iostreams::bzip2_decompressor());
        in.push(MyInputEncryptionFilter());
        in.push(boost::iostreams::bzip2_decompressor());
        in.push(boost::iostreams::file_source(filename, BOOST_IOS::in | 
BOOST_IOS::binary));

        if (!in.is_complete())
        {
            std::cerr << "Error creating filtering input stream" << 
std::endl;
            return;
        }

        boost::archive::xml_iarchive input_archive(in);

         //deserialise file here
        return;
    }
    //various catches removed
}