[Boost-build] gcc.jam weirdness (was: Boost-1.36.0 FreeBSD patches for review)

Subject: [Boost-build] gcc.jam weirdness (was: Boost-1.36.0 FreeBSD patches for review)
From: Steve M. Robbins (steve_at_[hidden])
Date: 2008-10-24 04:04:16

On Thu, Oct 23, 2008 at 10:46:58PM -0400, Alexander Sack wrote:

> In the meantime, I would like comments on the following three patches:

> - gcc.jam.patch
> 
> The gcc toolset is set with a LD_LIBRARY_PATH without /lib.

My reading of the linux runtime loader manpage suggests that
LD_LIBRARY_PATH should be reserved for *NONSTANDARD* library
locations.  Here is an excerpt from "man ld-linux":

    The necessary shared libraries needed by the program are searched
    for in the following order

    o   Using the environment variable LD_LIBRARY_PATH
        (LD_AOUT_LIBRARY_PATH for a.out programs).  Except if the
        executable is a setuid/setgid binary, in which case it is
        ignored.

   o    From the cache file /etc/ld.so.cache which contains a compiled
        list of candidate libraries previously found in the augmented
        library path.

   o    In the default path /lib, and then /usr/lib.

In my view, it would be a mistake to add /lib.  Alexander: what
problem does that solve for you?

Reading gcc.jam (from trunk) I find this bit at line 160:

    # If gcc is installed in non-standard location, we'd need to add
    # LD_LIBRARY_PATH when running programs created with it (for unit-test/run
    # rules).
    if $(command)
    {
        # On multilib 64-bit boxes, there are both 32-bit and 64-bit libraries
        # and all must be added to LD_LIBRARY_PATH. The linker will pick the
        # right onces. Note that we don't provide a clean way to build 32-bit
        # binary with 64-bit compiler, but user can always pass -m32 manually.
        local lib_path = $(root)/bin $(root)/lib $(root)/lib32 $(root)/lib64 ;
        if $(.debug-configuration)
        {
            ECHO notice: using gcc libraries :: $(condition) :: $(lib_path) ;
        }
        toolset.flags gcc.link RUN_PATH $(condition) : $(lib_path) ;
    }

The comment introducing this block seems correct, to me.  However, it
appears that the $(lib_path) is set and used regardless of whether gcc
is installed in a standard or non-standard location.  Is this correct,
or am I misreading the jam file?

As mentioned above, I don't think you want to have standard library
locations added to the link line.  It appears that $(root) is set to
the root install directory of gcc.  So if root is /usr, will /usr/lib
and friends be added to the link line?

Finally, $(root)/bin looks plain wrong.  Is it a Microsoft thing?

Regards,
-Steve