RE: Linker errors using third-party library

[Emmanuel Stapf]

Hi,

This is an issue with the provider of the third-party library and the fact that
Microsoft have many ways to generate C code using the Microsoft C runtime library:
non-MT came with two variants (static and dynamic), MT came with the same
variants. In addition you have one more variation: debug vs non-debug version of
the libraries. And of course those are incompatible. In the Linux world this is
much easier, there is only one C runtime library.

We generate the code using /MT because this is the most widely used out there.

The easiest is to get the third-party library to be compiled with /MT and you
check with the provider on how to get this.

If this is not possible, then using -NODEFAULTLIB:libcmt in the linker flags would
have been the correct way to fix the errors, unfortunately it is most likely
guaranteed that the code will not work properly.

Thus the only thing you have left is to change the C compilation options from the
Eiffel configuration to compile your code using /MD including our runtime and all
the C code included in our libraries.

Manu

> -----Original Message-----
> From: eiffel_...@yahoogroups.com
> [mailto:eiffel_...@yahoogroups.com] On Behalf Of David Jenkins
> Sent: Thursday, October 11, 2012 10:09
> To: eiffel_...@yahoogroups.com
> Subject: [eiffel_software] Linker errors using third-party library
>
> I've hit a snag building an Eiffel project for Windows7 that links a
> third-party static library. The third-party library is delivered as a MS
> Visual C++ 2010 solution with all necessary source files for creating the
> static library. It built successfully as delivered; I've made no changes
> to the Visual C++ solution configuration. I've added the .lib file that
> Visual C++ created to my Eiffel project as an external object, together
> with the necessary Includes. When I freeze the project, the Eiffel code
> compiles successfully, and the C++ compile also succeeds. However the
> linker raises a multitude of errors, all similar to this:
>
> 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 LIBCMT.lib(typinfo.obj)
>
> After it's finished disgorging errors, it registers this final bit of
> advice:
>
> LIBCMT.lib(crt0init.obj) : warning LNK4098: defaultlib 'msvcrt.lib'
> conflicts with use of other libs; use /NODEFAULTLIB:library
> re2_test.exe : fatal error LNK1169: one or more multiply defined symbols
> found
>
> Is there something wrong with the way I've built the third-party library,
> or with the way I've configured my Eiffel project? The presence of many
> errors all refencing a conflict with LIBCMT.lib made me suspect that the
> third-party library was built as a multi-threaded solution (my Eiffel
> project is not multi-threaded), but I've checked and the Visual C++
> linker that built the third-party library is set to use /MD and not /MT
> (which I think means "build as a non-multi-threaded library").
>
> I also tried adding an "Externals | Linker flag" to my Eiffel external
> configuration, with Value = /NODEFAULTLIB:LIBCMT.lib. Whether or not this
> is correct, it had the unexpected result of adding the string
> "/NODEFAULTLIB:LIBCMT.lib" to the list of libraries to link and not as a
> linker flag, and of course raised an error. Should the "Externals |
> Linker flags" configuration option be used this way for Windows? Is
> adding this flag even the right way to solve my problem?
>
> I'd really appreciate any suggestions for fixing these linker issues.
>
> (BTW, I've built the same Eiffel project on Ubuntu, using the third-party
> library's Linux version. Everything works correctly there.)
>
> David Jenkins
>
>
>
> ------------------------------------
>
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>
>
>


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[Seref Arikan]

Hi David,
I can understand the frustration. It took me an incredible amount of time
to get these settings right under windows. No problems under Ubuntu,
exactly as you said.
The problem is the brilliant(!) way MS toolchain is managing runtime
libraries. The biggest issues is always md/mt thingie. Plus, there is this
very hard to find checkbox somewhere in the visual C++ settings that stops
the linker automatically linking libraries simply because it finds some
reference in a weird location and decides to act smart. Unfortunately, that
setup is in a virtual machine that I can't seem to find at the moment.

My best bet would be that the library and Eiffel are using different
settings of MS c++ compiler. Maybe Eiffel is compiling with MT. So the
easiest thing you may try is to try to switch the 3rd partly library to MT
and try to compile that way. If I manage to find my virtual machine setup,
I'll let you know how I was doing this (I was using protocol buffers and
zeromq with Eiffel)

Kind regards
Seref


On Thu, Oct 11, 2012 at 6:09 PM, David Jenkins <djenki...@yahoo.com>wrote:

> **

[Non-text portions of this message have been removed]

[David Jenkins]

I've hit a snag building an Eiffel project for Windows7 that links a third-party static library. The third-party library is delivered as a MS Visual C++ 2010 solution with all necessary source files for creating the static library. It built successfully as delivered; I've made no changes to the Visual C++ solution configuration. I've added the .lib file that Visual C++ created to my Eiffel project as an external object, together with the necessary Includes. When I freeze the project, the Eiffel code compiles successfully, and the C++ compile also succeeds. However the linker raises a multitude of errors, all similar to this:

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 LIBCMT.lib(typinfo.obj)

After it's finished disgorging errors, it registers this final bit of advice:

LIBCMT.lib(crt0init.obj) : warning LNK4098: defaultlib 'msvcrt.lib' conflicts with use of other libs; use /NODEFAULTLIB:library
re2_test.exe : fatal error LNK1169: one or more multiply defined symbols found

Is there something wrong with the way I've built the third-party library, or with the way I've configured my Eiffel project? The presence of many errors all refencing a conflict with LIBCMT.lib made me suspect that the third-party library was built as a multi-threaded solution (my Eiffel project is not multi-threaded), but I've checked and the Visual C++ linker that built the third-party library is set to use /MD and not /MT (which I think means "build as a non-multi-threaded library").

I also tried adding an "Externals | Linker flag" to my Eiffel external configuration, with Value = /NODEFAULTLIB:LIBCMT.lib. Whether or not this is correct, it had the unexpected result of adding the string "/NODEFAULTLIB:LIBCMT.lib" to the list of libraries to link and not as a linker flag, and of course raised an error. Should the "Externals | Linker flags" configuration option be used this way for Windows? Is adding this flag even the right way to solve my problem?

I'd really appreciate any suggestions for fixing these linker issues.

(BTW, I've built the same Eiffel project on Ubuntu, using the third-party library's Linux version. Everything works correctly there.)

David Jenkins

[David Jenkins]

Hi Manu and Seref,

Many thanks for the replies. Changing the third-party solution's linker flag to /MT did the trick! My Eiffel project now compiles and links successfully.