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Date: Fri, 24 Aug 2012 13:40:00 -0000
Message-ID: <CAH6eHdRpxoPerOwyf0kPhJjCvJDZQqpC7xYCZpu3wj_Va9yjZg@mail.gmail.com>
Subject: Re: libstdc++
From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: naga raj <gnuuser.raj@gmail.com>
Cc: gcc-help <gcc-help@gcc.gnu.org>
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On 24 August 2012 08:46, naga raj wrote:
> Hi,
>
>    I have ported Gcc-4.6.2 to an embedded target. My C++ compiler is
> generating huge code size.
>
>   #include <iostream>
>  using namespace std;
>  int main()
>  {
>    return 0;
>  }
>
>    If we execute the above program then all the function in the
> iostream library are included in the elf as a result size of elf is
> increased....

Including <iostream> causes global objects to be constructed, so even
though you're not explicitly using std::cout or std::cin, those
streams are initialized and code is run (before main) just because
<iostream> is included.  If you don't need to use it then don't
include it.  If you do need to use it then obviously the code size is
larger if you use I/O features than if you don't use them.

That said, libstdc++ isn't really optimised for embedded systems.
Some configure-time options such as building libstdc++ without
exceptions can help reduce code size, if you don't need to use
exceptions.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43852 would also help
avoid dependency on the I/O facilities.