Re: rtld or lang/gcc cannot find libgcc_s.so.1

On Tue, 21 Feb 2012, Steve Kargl wrote:

> On Tue, Feb 21, 2012 at 05:00:53PM -0500, Diane Bruce wrote:
>> On Tue, Feb 21, 2012 at 10:37:15PM +0100, Dimitry Andric wrote:
>>> On 2012-02-21 20:42, Steve Kargl wrote:
>>> ...
>>>> Yes, /lib comes before /usr/local/lib/gcc46.  I suppose
>>>> that this is a heads up for gerald_at_. lang/gcc is used by
>>>> the ports collections to build a large number of other
>>>> ports, so others are likely to hit this issue.
>>
>> Does -rpath not help ?
>
> I already mentioned that I can add '-rpath /usr/local/lib/gcc46'
> to my various projects.  I can also build with -static to avoid
> rtld.  One can also use LD_LIBRARY_PATH.
>
> The issue seems to be that lang/gcc will be installed after
> system start, and 'ldconfig -m' appends new shared libraries
> to the hints file.  This means that libraries with the same
> name but different locations will be found via the order of the
> search path in the hints file, and one gets the wrong library.
> That is, with the following
>
> troutmask:root[256] ldconfig -r | grep libgcc_s
>        29:-lgcc_s.1 => /lib/libgcc_s.so.1
>        723:-lgcc_s.1 => /usr/local/lib/gcc46/libgcc_s.so.1
>
> 29 will be found before 723.  While I can work around the
> issue, lang/gcc is used by a rather large boatload of ports
> during the building process and I suspect that a large
> number of FreeBSD users use lang/gcc for their everyday
> compiler.  The question is how do we, the FreeBSD project,
> deal with this issue, so that the general user base does not
> get hit with it.

I think there is perhaps a little more to this issue of multiple 
(incompatible) copies of a library with the same name being installed, 
e.g. libcom_err in /usr/lib/libcom_err.so and 
/usr/local/lib/libcom_err.so.  An application using the library must 
#include <com_err.h> to get the library prototypes, but the preprocessor 
puts the standard include search path /usr/include at the end of the 
search list, even if it is specified explicitly on the command line, 
unless -nostdinc is passed. So this will prefer the header from ports in 
the absence of evil trickery.

I was pounding my head against this a couple years ago, so my memory is 
not quite fresh, but I think that I could convince the compile-time link 
step to use either version of the library with the appropriate ordering of 
-L arguments (but I am in trouble if I want libkrb5.so from ports and 
libcom_err.so from base!).

In any case, the dynamic linker will search the default search path 
*first*, preferring the copy of the library from the base system.  After 
pounding my head against the issue for a while I concluded that I had no 
option other than to use -rpath (but alas I ran out of time for that 
particular project and never finished).

It is definitely an ugly situation and I have no good answers.  It would 
be nice to not have to specify every detail of what should be happening, 
though.

>
> There are a few solutions:
> 1) Set ldconfig_paths in /etc/rc.conf to cause ${PORTSDIR}/lib to
>   be scanned before /lib and /usr/lib.
> 2) Use /etc/ld.so.conf to cause ${PORTSDIR}/lib to be scanned
>   for /lib and /usr/lib.
> 3) Add a new option to ldconfig to prepend new libraries to
>   the hints files and fix the ports to use this option instead
>   of -m.
> 4) Suggestions from people that are brighter than I.

How would things break if we made everything in the base system specify 
-rpath of /lib and /usr/lib as appropriate, and then put the ports 
versions first in the default search path?

-Ben Kaduk