rustc -o - crashes

[ghost]

When I tried this, I was hoping it would output the executable to stdout. Saving it as a file called - would be reasonable behavior too.

$ ls
example.rs
$ rustc -o - example.rs
error: linking with `cc` failed: exit code: 1
note: "cc" "-Wl,--as-needed" "-m64" "-L" "/usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "-" "-.o" "-Wl,--whole-archive" "-lmorestack" "-Wl,--no-whole-archive" "-Wl,--gc-sections" "-pie" "-nodefaultlibs" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-7d23ff90.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcollections-7d23ff90.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_unicode-7d23ff90.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/librand-7d23ff90.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-7d23ff90.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-7d23ff90.rlib" "/usr/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-7d23ff90.rlib" "-L" "/usr/lib64/rustlib/x86_64-unknown-linux-gnu/lib" "-L" "/home/d/tmp/x/.rust/lib64/x86_64-unknown-linux-gnu" "-L" "/home/d/tmp/x/lib64/x86_64-unknown-linux-gnu" "-Wl,--whole-archive" "-Wl,-Bstatic" "-Wl,--no-whole-archive" "-Wl,-Bdynamic" "-ldl" "-lpthread" "-lrt" "-lgcc_s" "-lpthread" "-lc" "-lm" "-lcompiler-rt"
note: cc: error: unrecognized command line option ‘-.o’

error: aborting due to previous error
$ ls
example.rs  -.metadata.o  -.o

[steveklabnik]

Triage: no change.

[Mark-Simulacrum]

I almost want to say that this isn't a bug. Do gcc and clang handle this case? I feel like it would be odd to write the compiler's output (binary data) to stdout.

[ghost]

gcc and clang both output to a file called -:

$ ls
example.c
$ gcc -o - example.c
$ ls
-  example.c
$ ./-
Hello, world!
$ rm -- -
$ clang -o - example.c
$ ls
-  example.c

[steveklabnik]

Triage: no change

[lenary]

It would be nice if we could still output to stdout in the case where rustc is writing printable output. If you do gcc -S -o - example.c, it should output to stdout, same with clang, and same for clang's -emit-llvm option.

[Enselic]

The issue is fixed:

$ cat main.rs
fn main() {
    println!("yep, it works")
}
$ rustc -o - main.rs > ./does-it-work && chmod +x does-it-work && ./does-it-work
yep, it works

But it looks like the fix forgot to write a regression test for the non---emit case, i.e. plain rustc -o -.

We should add such a test before we close this issue.

@rustbot label E-needs-test

[ojoj42]

@rustbot claim

[Josu-ke]

Hi team would like to contribute to the project as a beginner to rust. I see that the task is to add a unit test? Is this available?

[Josu-ke]

@rustbot claim

[Josu-ke]

I am going to give it a shot.
Seems the change should be to the Makefile in rust/tests/run-make/emit-to-stdout?