Re: cout printing ints in hexadecimal instead of decimal

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 2 Oct 2009 10:01:18 -0700 (PDT)

Message-ID:

<4a80de83-c4e6-4354-afcf-318c2d046697@c37g2000yqi.googlegroups.com>

On Oct 2, 1:58 pm, Diwa <shettydiwa...@gmail.com> wrote:

OP here. Thanks to all who responded.

Here are some facts. This program is multi-threaded (we know
iostreams are not thread safe).

On days when the cout screwup happens, right during program
startup, the logs show that while one thread is in the middle
of printing addr of a memory location using cout (hex by
default), another thread interrupts it with its own cout.

I know of no implementation which can handle this. You need
some sort of external synchronization for all of your output to
any given instance of an ostream. (You should not need
synchronization for output to different instances.)

Maybe since the first thread was in the middle of printing
addr in hex format when it got interrupted, the hex flag
remained set. Just guessing.

Something like "std::cout << std::hex << someInt" resolves to:
operator<<( std::cout, std::hex ).operator<<( someInt )
There's no way the implementation can prevent a thread switch
between the two calls to operator<<; it's in user code. It's up
to you to ensure that the stream object is properly
synchronized.

--
James Kanze