Gold fails to make a relocatable object file from a static library

Question

Let me preface this by saying that I'm a noob in things related to linkers. If something I say seems like it makes no sense, it probably doesn't - please call me out on it.

---

I've got the following files:

• bar.rs

  #[no_mangle]
  pub extern fn bar(x: isize) -> isize { x + 1 }
  

• foo.c

  extern int bar(int);
  extern int baz(int);
  int foo(int x) { return bar(x) + baz(x); }
  

I can link these into one relocatable object file with:

$ rustc --crate-type=staticlib bar.rs -o bar.a
$ gcc -c foo.c -o foo.o
$ ld -r foo.o bar.a -o out.o

I'm not sure what is happening under the hood, but I sure do get the output I wanted: bar and foo are defined while baz isn't.

$ nm out.o | grep '\(foo\|bar\|baz\)$'
0000000000000000 T bar
                 U baz
0000000000000000 T foo

Exactly the same thing happens if I replace ld with ld.bfd. However, things fall apart with ld.gold.

$ ld.gold -r foo.o bar.a -o out.o
ld.gold: internal error in set_info_section, at ../../gold/output.h:3198

This is with both ld.gold packaged with binutils 2.24 and 2.26.

The problem persists with binutils 2.30, although the line number I get is different:

$ ld.gold -r foo.o bar.a -o out.o
ld.gold: internal error in set_info_section, at ../../gold/output.h:3386

Also, the error persists even with --emit=obj instead of --crate-type=staticlib

So:

• What does the error mean?
• How can I achieve the same relocatable object output with ld.gold as with ld and ld.bfd?

Answer 1

Reported here. Turns out this is already fixed in trunk, so I guess the solution is to wait until binutils 2.31 (or build binutils from scratch).

Answer 2

What does the error mean?

It means that Gold is failing internal assertion. Probably this one.

How can I achieve the same relocatable object output with ld.gold as with ld and ld.bfd

You need to either fix Gold to handle this input, or to change the input so it doesn't trigger the bug.

Since neither you nor I understand exactly what the bug triggering conditions are, the first step should be to file a bug in bugzilla.

There is already a very similar bug. Not sure if you are hitting the same issue though.