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    SubjectRe: [PATCH] Add a /proc/self/exedir link
    On Thu, 6 Apr 2006, Mike Hearn wrote:

    > > IMO the program must be aware of the get-my-exedir feature, just configuring
    > > --prefix=/proc/... is aiming for your feet.
    > I disagree, though /proc/self/exedir may not be the right answer. The
    > problem with the original proposal is there's no concept of a group
    > leader to which files are resolved relative to so there is this problem
    > with child processes.

    The problem ist the word 'the'. If parent and child are using 'the foo',
    they will clash.

    > I sent a mail outlining a scheme that used file descriptor passing to
    > achieve the same effect but with the needed "inheritance" of the path,
    > but, vger seems to have munched it! At least I don't see it on the gmane
    > archives. But the scheme is simple enough:
    > * get_prefix() reads /proc/self/exe and turns it into the correct
    > directory
    > * dup2(open(get_my_exedir()), 999)
    > * ./configure --prefix=/proc/self/fd/999

    bin/foo calls bin/bar refering to /proc/self/fd/999
    bin_2/bar does dup2(open(get_my_exedir()), 999) ***FUBAR***

    possible solution:

    don't dup2, and only close fds you opened yourself.

    Disadvantage: Leaky (too), may break scripts.

    .oO(Can you chroot a single filedescriptor or somehow make
    /proc/self/fd/$n/.. be unavailable?)

    > It also restricts the problem to passing paths to other processes that
    > are not subprocesses (eg via rpc). But as each process can have its own
    > namespace this will always be an issue that needs careful treatment, and
    > the pain of adjusting software to realpath() it is much lower than
    > modifying every path in every piece of software. That approach was
    > already tried and sucks.

    There may be no "real path" corresponding to /proc/self/fd/4711.

    IMO it's still best to just symlink the program directory to the correct
    place and make the programs search in e.g. ~/opt/ and /opt/.
    Fun things to slip into your budget
    An abacus
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