[Christian, please chime in] On Oct 24 20:41, Denis Excoffier wrote: > > On 2014-10-24 13:02, Corinna Vinschen wrote: > > On Oct 23 20:06, Denis Excoffier wrote: > >> On 2014-10-22 11:23, Corinna Vinschen wrote: > >>> > >>> - Drop the current working directory from the default DLL search path in > >>> favor of Cygwin's /bin dir. > >> I'm not so comfortable with this one. > >> > >> I use > >> PATH=/my/dir/bin:/usr/bin /my/otherdir/myprog > >> > >> There is no DLL at all in /my/otherdir (this is the very first place > >> for Windows to look for DLL's, and i think that this cannot change). > >> In /my/dir/bin, there is an updated version of a library also > >> located in /usr/bin, for example an updated cygstdc++-6.dll (from GCC > >> 4.9.1). > >> > >> Does this mean that, under this change, cygstdc++-6.dll will be found > >> in /usr/bin and not in /my/dir/bin ? In fact, this is what i can > >> observe personnally. > >> > >> Also, i don't remember that the CWD has an impact on where DLL is found > >> (apart > >> from being in PATH, and apart from being the dir where the exe resides). > >> > >> For a test i have commented out in cygheap.cc the line > >> 'wcpncpy (installation_dir, ...' (and also the next one) > >> and the old behaviour is now back. > >> > >> It seems to me that this change is a regression. Could someone please > >> argue? > > > > Hmm. It's hard to do the right thing here, I guess. I can see how > > this is a regression in your scenario. OTOH, your scenario is not > > stable. The directories in $PATH are the last ones in the DLL search > > order. So, your scenario already wouldn't work if your CWD is /bin > > (or /usr/bin). > Typically, the line 'PATH=/my/dir/bin:/usr/bin /my/otherdir/myprog' is > in a Makefile, as part of some 'make check'. I don't usually build > from /usr/bin.
Sure. I was just pointing out that it's not a 100% stable method, but
dependent on the system's DLL search order, your CWD, and the fact that
the application is not installed into {/usr}/bin.
> I was not aware that CWD was useful. IIUC, your change removes the lookup
> into CWD (and replaces with a lookup to somewhere else). Who needs CWD at
> the first place? These people (or specification?) will not be OK now.
If applications do this:
chdir("/path/of/DLLs");
dlopen("some.dll");
it wouldn't work anymore. It wouldn't work on Linux either, unless CWD
is in LD_LIBRARY_PATH or the default search path. This would work,
though:
chdir("/path/of/DLLs");
dlopen("/path/of/DLLs/some.dll");
Unfortunately the same doesn't work if the application calls execve
instead of dlopen because we can't add our LD_LIBRARY_PATH magic
there.
> > From Cygwin's POV {/usr}/bin is a system dir. For security reasons it
> > makes sense that the system DLLs in /bin cannot be overridden, unless
> > it's an installation issue which should be covered by looking into the
> > application installation dir first.
>
> Instead of adding the lookup of /usr/bin before the PATH, you could add
> it afterwards?
No. You don't expect this kind of flexibility in the Win32 API, do you?
The way it works is, there's a call SetDllDirectory which replaces the "."
in the DLL search path with the directory given as argument. The search
order is always this:
application dir
dir given in SetDllDirecory (Cygwin's bin)
system dirs
$PATH
> Or do you mean that my use is bad practice for security
> reasons? That there might be some unexpected DLL somewhere in the PATH?
> IIRC, in linux/solaris, LD_LIBRARY_PATH is not honored when you are root,
> not otherwise.
Not quite. LD_LIBRARY_PATH is only ignored if the excutable is a
suid/sgid executable. Unfortunately we don't have LD_LIBRARY_PATH at
all when running execve (but we have in dlopen).
> > Having said that, moving your DLLs into the application dir is really
> > not an option?
> Oh yes, i use it all the time. It is the job of 'make install' to also
> install the appropriate DLLs. The point here is for 'make check'.
Yeah.
Sigh.
I don't like the idea either that this simple change breaks existing
scenarios. I'm inclined to revert this change.
Christian, would you mind terribly to re-add the tweak to postfix
to set $PATH?
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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