Output of independent artefacts might differ depending on unrelated options

Existence or lack of --crate-type=bin may influence output of other crate-type outputs. In general libfoo.a output by --crate-type=bin,staticlib and --crate-type=staticlib might be completely different.

For example using this foo.rs, this is the list of a few first symbols when built with --crate-type=bin,staticlib and this, when bin crate-type is absent.

This is a quirk in rust’s entry point semantics and how current middle/entry.rs is implemented.

1. The check whether the entry point is necessary or not should occur elsewhere.

   Simonas Kazlauskas at 2015-02-11 16:55:13

2. Triage: not aware of any changes here?

   Steve Klabnik at 2016-03-04 17:57:28

3. I think that not much has changed here. The individual outputs are different, but the overall diff is the same: entry points are included in staticlib with --crate-type bin.

   --- no-bin      2017-04-30 18:10:53.442645721 -0600
   +++ bin 2017-04-30 18:10:48.398648634 -0600
   @@ -1,5 +1,8 @@
   
    test.0.o:
   +0000000000000000 T main
   +                 U std::rt::lang_start::h8126425a59d3b4a0
   +0000000000000000 t test::main::hf4d700377696cbb0
   
    std-35ad9950c7e5074b.0.o:
                     U abort
   

   $ nm -C libtest.a | head -n 15
   
   test.0.o:
   
   std-35ad9950c7e5074b.0.o:
                    U abort
                    U accept
                    U backtrace_create_state
                    U backtrace_pcinfo
                    U backtrace_syminfo
                    U bind
   0000000000000000 r byte_str.3f
   0000000000000000 r byte_str.3r
   0000000000000000 r byte_str.4B
   0000000000000000 r byte_str.4D
   0000000000000000 r byte_str.4f
   
   $ nm -C libtest-bin.a | head -n 15
   
   test.0.o:
   0000000000000000 T main
                    U std::rt::lang_start::h8126425a59d3b4a0
   0000000000000000 t test::main::hf4d700377696cbb0
   
   std-35ad9950c7e5074b.0.o:
                    U abort
                    U accept
                    U backtrace_create_state
                    U backtrace_pcinfo
                    U backtrace_syminfo
                    U bind
   0000000000000000 r byte_str.3f
   0000000000000000 r byte_str.3r
   

   Mark Rousskov at 2017-05-01 00:14:43

4. I'm not sure why this is marked as rustbuild, it seems to affect all binaries. Going to move this to T-compiler.

   jyn at 2022-06-27 04:32:52