Date: Mon, 23 Apr 2007 02:13:47 +0300 From: Diomidis Spinellis <dds@aueb.gr> To: Andrew Pantyukhin <infofarmer@FreeBSD.org> Cc: hackers@FreeBSD.org Subject: Re: extern "C" and undefined reference Message-ID: <462BEC2B.5090508@aueb.gr> In-Reply-To: <cb5206420704221454v60a957b9qac74dc5f4f4b674a@mail.gmail.com> References: <cb5206420704221454v60a957b9qac74dc5f4f4b674a@mail.gmail.com>
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Andrew Pantyukhin wrote:
> 7zip developers converted some code from C++ to C,
> while leaving the main stand-alone lzma app in C++.
> They use 'extern "C" { }' blocks around #include's
> referencing C headers.
>
> Everything compiles fine, but "undefined reference"
> errors appear at linkage. The undefined references
> are to the C functions included from withing those
> 'extern "C"' wrappers. I tried to remove the
> wrappers from some files and the amount of errors
> decreased a bit. Is there a better workaround?
>
> Google came up with two results: remove the wrappers
> or use c++ instead of cc. I'm already using c++.
Many of the C headers are available in a different form for C++
programs. For example, in a C++ program you can #include <cstdio>
instead of <stdio.h>.
You can use nm(1) on the .o files to see where the problem comes from.
Diomidis
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