GNU bug report logs -
#26048
Use absolute file names in NEED instead of adding many entries to RUNPATH
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Reported by: ludo <at> gnu.org (Ludovic Courtès)
Date: Fri, 10 Mar 2017 15:02:02 UTC
Severity: normal
Tags: wontfix
Done: ludo <at> gnu.org (Ludovic Courtès)
Bug is archived. No further changes may be made.
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Message #8 received at 26048 <at> debbugs.gnu.org (full text, mbox):
Ricardo Wurmus <rekado <at> elephly.net> skribis:
> Andy wrote:
>
>> It would be pretty cool if we could fix our O(n^2) problems in search
>> paths in this core-updates -- basically whenever you go to create an
>> environment, instead of making e.g. VAR=A:B:C:..., for all VARs
>> (LIBRARY_PATH, PKG_CONFIG_PATH, etc), instead we make a union directory
>> Z containing the union of A, B, C, etc and set VAR=Z. The goal would be
>> to fix quadratic run-time lookup costs by replacing it with a
>> compile-time computation. This applies to many lookups: PATH, -rpath,
>> etc.
>
> Ludo wrote:
>
>> A possible alternative solution for ld.so is at
>> <https://bugs.gnu.org/26048>.
>
> Do you know of any negative side effects this would have? For example,
> would it not become impossible to override libraries at runtime with
> LD_LIBRARY_PATH or LD_PRELOAD when “-lfoo” is replaced by the absolute
> file name of the “foo” library?
Good question. Per the ELF v1.2 spec¹ (page 82), setting DT_NEEDED to
an absolute file name would prevent overriding via LD_LIBRARY_PATH,
which is not desirable.
It turns out we cannot even set DT_NEEDED to an absolute file name in
the first place, because ld records the DT_SONAME of the library, when
it’s available (which is the case most of the time), rather than its
file name.
IOW, the approach suggested in <https://bugs.gnu.org/26048> isn’t really
applicable. :-/
Ludo’.
¹ http://refspecs.linuxbase.org/elf/elf.pdf
This bug report was last modified 7 years and 183 days ago.
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