[cfe-dev] [RFC] Recognize -fuse-ld={bfd, gold, lld} but don't prepend "ld." or "ld64." for other values

[Keith Smiley via cfe-dev]

I like the idea of separating the "magic" discovery of fuse-ld and the path
based discovery so I'd be happy with that option!

On Tue, Jun 16, 2020 at 15:26 Fangrui Song via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> On 2020-06-03, Fangrui Song wrote:
> >On 2020-06-03, David Chisnall via cfe-dev wrote:
> >>On 02/06/2020 19:47, Fangrui Song via cfe-dev wrote:
> >>>If they use a relative path, they can't be benefiting from ld. prefix
> >>
> >>This depends on how they specify the path.  If they specify a path
> >>for the linker via -fuse-ld, they don't get the prefix.  Most
> >>cross-compile toolchains that I've seen don't do that.  Instead,
> >>they use -B to specify a path to find *all* of the tools and then
> >>use -fuse-ld={lld,gold,bfd,proprietary linker's name}.
> >>
> >>That is the use case I'm concerned about breaking.  The behaviour of
> >>-B is to prepend a search path, but still fall back to the default
> >>paths if a tool is not found there.  For example, if I have:
> >>
> >>/usr/bin/lld
> >>/my/custom/sdk/bin/ld.lld
> >>
> >>If I run:
> >>
> >>$ clang -B /my/custom/sdk/bin/ -fuse-ld=lld ...
> >>
> >>Today, I will run my cross-compile toolchain's linker.  With your
> >>proposed change, I will run my system LLD install.  As a user, I
> >>will see very confusing error messages from the system linker if it
> >>can't handle my cross-compile target.  Worse, I may see a binary
> >>linked with a linker that defaults to a different linker script, but
> >>still produces some output.
> >>
> >>David
> >
> >-fuse-ld={bfd,gold,lld} is compatible with the previous behavior.
> >
> >Do you propose that:
> >
> >* -fuse-ld={bfd,gold.lld} should find "ld.{bfd,gold,lld}" in COMPILER_PATH
> >* all -fuse-ld=word should find "word" in COMPILER_PATH
> >* -fuse-ld=relative/path should find "relative/path" in PATH?
>
> Thoughts?
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-- 
--
Keith Smiley
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