[Boost-users] [iostreams] Inconsistency b/w docs and code of stream()

27 Feb 2008

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Nitay Joffe wrote:
Hey guys,
I'm working with the boost::iostreams library to create a stream object
from
a Device class I've implemented. I'm trying to call the constructor that
allows setting of the buffer size and it is failing to compile on 64 bit.
I used the documenation at
http://www.boost.org/libs/iostreams/doc/guide/generic_streams.html#stream
The docs say the constructor is of the form:
stream(const T& t,
       std::streamsize buffer_size = default_value,
       std::streamsize pback_size = default_value);
My code to create the stream looks like:
MyDevice myDevice(...)
MyStream(myDevice, (std::streamsize)500);
On a 32 bit machine this works fine, but on a 64 bit one it does not
compile. The parameters I'm passing in are not matching up with a
Would you please post the compiler errors?
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Thanks,
-n
Sure, here is sample code that causes the error:

#include <iosfwd>
#include 
#include 

struct MyDevice {
  typedef char char_type;
  typedef boost::iostreams::source_tag category;

  std::streamsize read(char *s, std::streamsize n) {
    return n;
  }
};

typedef boost::iostreams::stream<MyDevice> MyStream;

int main() {
  MyDevice d;
  MyStream s(d, (std::streamsize)500);
  return 0;
}

And here are the compile errors:

g++ a.cc
k/usr/include/boost/iostreams/stream.hpp: In constructor
'boost::iostreams::stream::stream(U100&, const U0&) [with
U100 = MyDevice, U0 = std::streamsize, Device = MyDevice, Tr =
std::char_traits<char>, Alloc = std::allocator<char>]':
a.cc:18:   instantiated from here
/usr/include/boost/iostreams/stream.hpp:110: error: no matching function for
call to 'MyDevice::MyDevice(MyDevice&, const long int&)'
a.cc:5: note: candidates are: MyDevice::MyDevice()
a.cc:5: note:                 MyDevice::MyDevice(const MyDevice&)
make: *** [all] Error 1

If I change the (std::streamsize) to (int) it compiles.

Cheers,
-n