[PATCH 0/2] ARC Moving to @pcl relocations

Andrew Burgess andrew.burgess at embecosm.com
Thu Jul 28 18:20:12 UTC 2016

This is a slightly odd series of 2 patches.  The two patches are
actually alternative solutions to the same problem.  I'm keen to see
one of these merged, but I don't know which method would be preferred.

This commit aims to address an issue that was introduced / mentioned
in commit 20554a78a9bba278c6b9cbbb4cfc5bde3772c56d (ARC:
Conditionalise certain relocations as provided by TLS tools only).

The problem is that not all historic versions of binutils have
supported the @pcl relocation type.  This problem is compounded by the
fact that the arithmetic construct that was previously used to
synthesise an @pcl like behaviour, does not work on recent versions of

In the commit 20554a78a code was added that selects between the new
style @pcl relocations, and the old style arithmetic construct,
however, this selection is done based on whether the uClibc user has
configured with native threads or not.

Of course, a uClibc user could choose to use a modern version of
binutils AND configure without native thread support, in which case
uClibc will not compile.

I have two proposed solutions.  In patch 1/2 I simply drop support for
the older versions of binutils in favour of the new @pcl relocation
type.  This feels the cleanest solution, but I don't know how strongly
the uClibc(-ng) community feels about maintaining compatibility for
older versions of the tools.

Given that I anticipated push back against the first patch I took a
look at how I might maintain compatibility.  It turns out to be pretty
easy, and that is patch 2/2.  In this patch I drew inspiration from
similar examples in the Rules.mak file to check if the toolchain
supports @pcl relocations or not.  With this done we have a new define
based on the specific toolchain feature being supported or not, which
can then be used to conditionalise the code.

Would you consider merging one of these patches?


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