Can't specify linker to use with the -B flag

[llvmbot]

Bugzilla Link	10744
Resolution	FIXED
Resolved on	Sep 01, 2011 11:26
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor
CC	@efriedma-quic,@zmodem,@nico

Extended Description

$ clang -B/usr/x86_64-pc-linux-gnu/i686-pc-linux-gnu/binutils-bin/2.20.1-gold/ld test.c
uses linker at "/usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/../../../../x86_64-pc-linux-gnu/bin/ld" and ignores one specified by -B. To see it, use -v.

I think this is because of the following code:

In tools/clang/lib/Driver/ToolChains.cpp:

llvm::sys::Path LinkerPath(Base + "/../../../../" + GccTriple + "/bin/ld");
if (!llvm::sys::fs::exists(LinkerPath.str(), Exists) && Exists)
Linker = LinkerPath.str();
else
Linker = GetProgramPath("ld");

So it tries to use the first guess (/usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/../../../../x86_64-pc-linux-gnu/bin/ld) linker, and only if not found, it invokes ToolChain::GetProgramPath("ld", true), which calls Driver::GetProgramPath("ld", this, true):

In tools/clang/lib/Driver/Driver.cpp:

std::string Driver::GetProgramPath(const char *Name, const ToolChain &TC,
bool WantFile) const {
// Respect a limited subset of the '-Bprefix' functionality in GCC by
// attempting to use this prefix when lokup up program paths.
for (Driver::prefix_list::const_iterator it = PrefixDirs.begin(),
ie = PrefixDirs.end(); it != ie; ++it) {
llvm::sys::Path P(*it);
P.appendComponent(Name);
bool Exists;
if (WantFile ? !llvm::sys::fs::exists(P.str(), Exists) && Exists
: P.canExecute())
return P.str();
}
...

So it does respect -B, but only if the first guess not found.

[llvmbot]

The -B flag takes a path to a directory, not a path to the 'ld' file.

[llvmbot]

The -B flag takes a path to a directory, not a path to the 'ld' file.

Does not help unfortunately.
If it can find a first guess linker (see 1st code snippet in Description) - it uses it no matter what -B says.

And for cross-compiling it is a pain.

[llvmbot]

Thanks. I've created the relevant paths such that I can reproduce this on my system.

Rafael, you added the relevant code in r118382. Why? My system works fine without this, does GCC special-case this path for the linker only?

[llvmbot]

I was added for support for cases where gcc and ld are installed together. This is done for example in the toolchais codesourcery distributes. I think OpenSuse does it too.

I will see if I can keep the functionality but move it behind the -B options in the search.

[llvmbot]

test patch
Can you try this patch? I tested it on OpenSuse and it has the same effect, but I think -B will now take precedence.

[llvmbot]

Great, it works for me, please commit. Thank you!

[llvmbot]

Fixed in r138941.