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

[David Chisnall via cfe-dev]

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