Rustc build doesn't pass RUSTFLAGS "-L native=/path" to linker commands with -lffi

[apaprocki]

Carried over from rust-lang/cargo#4452 per @alexcrichton

I have libffi in a non-standard location. I set RUSTFLAGS to contain -L native=/path when building rustc itself. Cargo passes this -L path when compiling individual objects, but does not pass the -L path when attempting to link anything that also gets -lffi on the linker command line. The end result is that the link fails because -lffi can't be found.

edit: I worked around this by making a wrapper to gcc that passes the -L rule and passing it as the --default-linker option.

Example breakage, when RUSTFLAGS has -L native=/path:

Build failed, waiting for other jobs to finish...
error: Could not compile pulldown-cmark.

Caused by:
process didn't exit successfully: /dev/shm/rustc-1.19.0-src/build/bootstrap/debug/rustc --crate-name build_script_build /dev/shm/rust-1.19/debian/cargo_home/registry/src/github.com-1ecc6299db9ec823/pulldown-cmark-0.0.14/build.rs --error-format json --crate-type bin --emit=dep-info,link -C opt-level=2 -C metadata=94247588bee65632 -C extra-filename=-94247588bee65632 --out-dir /dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1-rustc/release/build/pulldown-cmark-94247588bee65632 -L dependency=/dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1-rustc/release/deps --cap-lints allow (exit code: 101)
--- stderr
error: linking with gcc failed: exit code: 1
|
= note: "gcc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m64" "-L" "/dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib" "/dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1-rustc/release/build/pulldown-cmark-94247588bee65632/build_script_build-94247588bee65632.0.o" "-o" "/dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1-rustc/release/build/pulldown-cmark-94247588bee65632/build_script_build-94247588bee65632" "-Wl,--gc-sections" "-pie" "-Wl,-O1" "-nodefaultlibs" "-L" "/dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1-rustc/release/deps" "-L" "/dev/shm/rustc-1.19.0-src/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" <a bunch of .rlib files> "-Wl,-Bdynamic" "-l" "ffi" "-l" "dl" "-l" "rt" "-l" "pthread" "-l" "ffi" "-l" "ffi" "-l" "ffi" "-l" "ffi" "-l" "ffi" "-l" "ffi" "-l" "gcc_s" "-l" "ffi" "-l" "ffi" "-l" "pthread" "-l" "c" "-l" "m" "-l" "rt" "-l" "pthread" "-l" "util" "-l" "ffi" "-l" "ffi"
= note: ld: cannot find -lffi
collect2: error: ld returned 1 exit status

[apaprocki]

(Even though that output was generated against rust 1.19, I verified the same thing happens with the current 1.24 release)

[cuviper]

This reminds me of #40717, where we found that -lfoo args are remembered by crates, but not -Lpath.

[jackh726]

I'm going to close this since there is no clear reproduction.