Unreadable error messages on linking failure

[fschutt]

This is a very annoying aspect of cargo - if it fails to link a library, it doesn't tell you the path, it doesn't tell you which library it couldn't find, it just spits out a completely unreadable error message and quits. For example:

   Compiling deflate v0.7.17
error: could not exec the linker `cc`: No such file or directory (os error 2)
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m64" "-L" "/home/felix/.rustup/toolchains/stable-
x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" 
"/home/felix/Development/srtmtoimage/target/debug/build/kernel32-sys-
23866d7aeb753806/build_script_build-23866d7aeb753806.build_script_build0.rust-cgu.o" "-o" 
"/home/felix/Development/srtmtoimage/target/debug/build/kernel32-sys-
23866d7aeb753806/build_script_build-23866d7aeb753806" 
"/home/felix/Development/srtmtoimage/target/debug/build/kernel32-sys-
23866d7aeb753806/build_script_build-23866d7aeb753806.crate.allocator.rust-cgu.o" "-Wl,--gc-
sections" "-pie" "-Wl,-z,relro,-z,now" "-nodefaultlibs" "-L" 
"/home/felix/Development/srtmtoimage/target/debug/deps" "-L" "/home/felix/.rustup/toolchains/stable-
x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" 
"/home/felix/Development/srtmtoimage/target/debug/deps/libbuild-055e23f8aa405a7b.rlib" 
"/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-
gnu/lib/libstd-fe0b1b991511fcaa.rlib" "/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-
gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librand-3d7b10e850a67e89.rlib" 
"/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-
gnu/lib/liballoc_jemalloc-28484309357fd6f1.rlib" "/home/felix/.rustup/toolchains/stable-x86_64-
unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc_system-751808ba756769d5.rlib"
 "/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-
gnu/lib/libpanic_unwind-8cb97051d8238386.rlib" "/home/felix/.rustup/toolchains/stable-x86_64-
unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunwind-25cc9b024a02d330.rlib"
 "/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-
gnu/lib/liblibc-d42e80cee81b06ce.rlib" "/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-
gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-78c21267a2dc15c1.rlib" 
"/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-
gnu/lib/libstd_unicode-0e1b544c94586415.rlib" "/home/felix/.rustup/toolchains/stable-x86_64
-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-0c5e3d6c117f8c44.rlib"
 "/home/felix/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-
gnu/lib/libcompiler_builtins-bd7cc5ada1e908e0.rlib" "-Wl,-Bdynamic" "-l" "dl" "-l" "rt" "-l" "pthread" "-l"
 "pthread" "-l" "gcc_s" "-l" "c" "-l" "m" "-l" "rt" "-l" "pthread" "-l" "util"

error: aborting due to previous error

error: Could not compile `rayon-core`.
warning: build failed, waiting for other jobs to finish...
error: Could not compile `kernel32-sys`.
warning: build failed, waiting for other jobs to finish...
error: build failed

Right, now try and read what the actual error is. Please:

• Don't just quit with "No such file or directory" - it's one of the most useless error messages ever. Please include at least the file name!
• If it is a linker error, please don't output the whole paths to the libraries. Just tell me which library wasn't found

That would be my suggestion for improving cargo. It's simply annoying to figure out which library is missing (99,99% it's a system dependency!). If this isn't part of cargo, ignore this issue.

[alexcrichton]

Thanks for the report! This error message is actually generated by rustc itself, so can this be reopened over there?

The message here indicates that cc itself is missing, which means that you probably need to install gcc or clang from your package manager. I agree that rustc could do a better job of letting you know this though!