Wireshark-dev: Re: [Wireshark-dev] Problems with epan\oids.c

From: Graham Bloice <graham.bloice@xxxxxxxxxxxxx>
Date: Mon, 17 Mar 2008 12:20:49 +0000
Peter Johansson wrote:
2008/3/17, Peter Johansson <peterjohansson73@xxxxxxxxx <mailto:peterjohansson73@xxxxxxxxx>>:

    2008/3/17, Bill Meier <wmeier@xxxxxxxxxxx
    <mailto:wmeier@xxxxxxxxxxx>>:

        Peter Johansson wrote:
        > 2008/3/13, Luis EG Ontanon <luis@xxxxxxxxxxx
        <mailto:luis@xxxxxxxxxxx> <mailto:luis@xxxxxxxxxxx
        <mailto:luis@xxxxxxxxxxx>>>:
        >
        >     On Thu, Mar 13, 2008 at 2:38 PM, Stig Bj�rlykke
        <stig@xxxxxxxxxxxxx <mailto:stig@xxxxxxxxxxxxx>
        >     <mailto:stig@xxxxxxxxxxxxx <mailto:stig@xxxxxxxxxxxxx>>>
        wrote:
        >      >  I suppose we have to leave them allocated if we don't
        know how
        >     libsmi
        >      >  is compiled?
        >      >  I have almost no experience on Windows, do we compile
        this our self?
        >
        >     I compiled it, I just made changes to the makefile (and
        build only the
        >     dll), I have no clue whether HAVE_VASPRINTF was defined
        or not.
        >
        >
        > Did you compile it using MSVC 6? Could this then be of the
        same type of
        > issue that is with adns, hence it is required to recompile
        libsmi too if
        > using another compiler for Wireshark on Windows than MSVC 6.
        Developer
        > Studio 2005EE for instance?
        >

        My 2 cents ....

        1. As noted previously: the problem is that there are (in effect)
           malloc(...) statements in libsmi which allocate storage and
        free(...)
           statements in oids.c to free that storage.

           This is a non-starter on Windows if libsmi.dll is linked
           against a different msvcrt than wireshark. (Think allocating
           memory in one heap and trying to free it in a completely
           different heap). This is the case if Wireshark is built,
           for example, using vc 2005EE(using msvcr80.dll) since
           our version of the Windows libsmi is currently built
           with vc6 (using msvcrt.dll).

           (If this 'gotcha' isn't mentioned someplace in the
        developer docs, it
            probably should be. If needed, I'll add something about the
            whole issue of using mixed run-time MSVCRT libraries
            with Wireshark on Windows).

        2. Possible solutions:

           a. (As a temporary workaround for anyone wishing to able to
              build a working Wireshark with other than vc6 which uses
              the current libsmi: Remove the free(...) statements in
        oids.c).
           b. Compile libsmi as part of the build process (like adns &
        etc).
              (It would be really nice not to have to do this ....).
           c. Looking at the smi code: there's a smiFree function in
              the smi file utils.c which seems like it might be
              just what is needed.
              However there's something to do with an
              #ifdef HAVE_DMALLOC_H which I don't altogether
        understand. Maybe
              this can be ignored since I'm pretty sure that our vanilla
              Windows build done using the makefile mentioned previously
              does not define this symbol.
              If so, a solution might be (on Windows only):
              1. exporting smiFree from libsmi (and then rebuilding
                 the library);
              2. adding an extern smiFree(void *ptr) to oid.c;
              3. changing the various free(...) statements in oids.c to
                 smiFree(...).

                 (Obviously it would be much cleaner if smiFree were
        available
                 as part of the API so that it could be used on any
                 platform. Or: maybe there's another better way .....
                 Possibly we could ask upstream if something can be done).


              Also: I don't think it makes any difference whether
              HAVE_VASNPRINTF & etc were defined when the Windows libsmi
              was built.
              Whether a library version of vasnprintf  or the libsmi
              version is used, storage is allocated and would need to
        be freed.


        Thoughts ??


        Bill

I believe that adding information to for instance README.developer
    on what is required to be done by developers on Windows due to the
    mix of msvcr80.dll and msvcrt.dll would be good. Would you (Bill)
    please add something in line with what you wrote above?
Personally I would want to go with 2c (for adns as well) since it
    is then possible to debug even this code. The pre-compiled
    libraries adns and smi will probably continue to generate problems
    since Windows based developers probably tend to shift more and
    more from VC6 to any of its successors (especially 2005EE).
    With adns it should be easier than with smi since adns at least
    comes with build support for Windows. But there is no such thing
    for smi. I guess that's why it was added already compiled since
    nobody actually wants to maintain the makefiles of a third party
    library.
However, another approach might be possible here. One where nobody
    needs to maintain (at least not continuously) the makefiles for
    these libraries:
    We could provide precompiled versions of both adns and smi using
    different versions of Visual Studio and Developer studio. It would
    then be possible to link the binaries with whatever version that
    matches the MSVC_VARIANT variable (config.nmake). Does anyone know
    if there are more versions of the MS VC runtime library than
    msvcr80.dll and msvcrt.dll? Is perhaps msvcrt.dll required only by
    VC6 and msvcr80.dll required for the rest of them?
/ Peter


When it comes to adns, the only thing that prevents it from being included in the ordinary build (apart from adding it to the Wireshark makefiles) is that a file in the adns Win32 distribution contains references to the "program files" directory on Windows spelled in some language. The file in question is adns_dll.dep (located in adns-1.0-win32-05\adns_win32\adns_dll). All lines that begin with "..\..\..\..\..\..\programfiler" can be safely removed from the adns_dll.dep file (it seems to me that they are there only to trigger a re-compilation if, lets say, Windows update provides new versions of the SDK files). Perhaps we could ask of Jarle (jgaa) Aase to remove these lines from his distribution?

See also http://bugs.wireshark.org/bugzilla/show_bug.cgi?id=2075 for an attempt to fix the adns issue with versions other than MSVC 6. If we are going to contact jgaa, updating his makefiles to allow CFLAGs to be passed in would be nice as well.

--
Regards,

Graham Bloice