Re: Migrating from VC6 to VS2005

From:

"Carl Daniel [VC++ MVP]" <cpdaniel_remove_this_and_nospam@mvps.org.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 18 Jun 2008 06:48:52 -0700

Message-ID:

<#q8bMoU0IHA.1768@TK2MSFTNGP03.phx.gbl>

Cartoper wrote:

I checked the Runtime Library over to Multi-threaded Debug (/MTd).
The license module is a static library I wrote that this project uses
that is still compiled with VC6, I have both MTd and MDd versions of
it, so I set this project to link to the MTd version and I am getting
the following errors:

2>EventData.obj : warning LNK4075: ignoring '/EDITANDCONTINUE' due to
'/INCREMENTAL:NO' specification
2>MSVCRT.lib(MSVCR80.dll) : error LNK2005: _free already defined in
LIBCMTD.lib(dbgheap.obj)
2>MSVCRT.lib(MSVCR80.dll) : error LNK2005: _realloc already defined in
LIBCMTD.lib(dbgheap.obj)
2>MSVCRT.lib(MSVCR80.dll) : error LNK2005: _malloc already defined in
LIBCMTD.lib(dbgheap.obj)
2>MSVCRT.lib(MSVCR80.dll) : error LNK2005: _memmove already defined in
LIBCMTD.lib(memmove.obj)
2>MSVCRT.lib(ti_inst.obj) : error LNK2005: "private: __thiscall
type_info::type_info(class type_info const &)" (??
0type_info@@AAE@ABV0@@Z) already defined in LIBCMTD.lib(typinfo.obj)
2>MSVCRT.lib(ti_inst.obj) : error LNK2005: "private: class type_info &
__thiscall type_info::operator=(class type_info const &)" (??
4type_info@@AAEAAV0@ABV0@@Z) already defined in
LIBCMTD.lib(typinfo.obj)

This indicates that you're linking code that's been compiled with two
different runtime library settings. (i.e. some that's been compiled /MT and
some that's been compiled /MD). You can use /NODEFAULTLIB:MSVCRT.LIB in the
linker arguments to suppress the loading of MSVCRT.LIB as an implicit
dependency.

As David indicated, in general you can't mix VC6 and VC8/9 code in the same
link. That said, there are many cases that do in fact work. In particular,
if the code is C or close to it, it'll likely work. If the code has no
dependencies on MFC, ATL or the C++ standard library, it'll likely work.
The only combination guaranteed to work, however, is to compile everything
with the same version of the compiler.

-cd