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Rollup merge of #85772 - luqmana:ignored-metadata, r=petrochenkov

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Preserve metadata w/ Solaris-like linkers.

#84468 moved the `-zignore` linker flag from the `gc_sections` method to `add_as_needed` which is more accurate but Solaris-style linkers will also end up removing an unreferenced ELF sections [1]. This had the unfortunate side effect of causing the `.rustc` section (which has the metada) to be removed which could cause issues when trying to link against the resulting crates or use proc macros.

Since the `-zignore` is positional, we fix this by moving the metadata objects to before the flag.

[1] Specifically a section is considered unreferenced if:
* The section is allocatable
* No other sections bind to (relocate) to this section
* The section provides no global symbols

https://docs.oracle.com/cd/E19683-01/817-3677/6mj8mbtbs/index.html#chapter4-19
This commit is contained in:
Yuki Okushi 2021-06-06 19:11:17 +09:00 committed by GitHub
commit d69cd46761
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1 changed files with 6 additions and 3 deletions
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9
compiler/rustc_codegen_ssa/src/back/link.rs
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@ -1836,10 +1836,16 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
// Make the binary compatible with data execution prevention schemes.
cmd.add_no_exec();
// OBJECT-FILES-YES
add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
// NO-OPT-OUT, OBJECT-FILES-NO
// Avoid linking to dynamic libraries unless they satisfy some undefined symbols
// at the point at which they are specified on the command line.
// Must be passed before any dynamic libraries.
// On solaris-like systems, this also will ignore unreferenced ELF sections
// from relocatable objects. For that reason, we move the metadata objects
// to before this flag as they would otherwise be removed.
cmd.add_as_needed();
// NO-OPT-OUT, OBJECT-FILES-NO
@ -1891,9 +1897,6 @@ fn linker_with_args<'a, B: ArchiveBuilder<'a>>(
// dynamic library.
cmd.export_symbols(tmpdir, crate_type);
// OBJECT-FILES-YES
add_local_crate_metadata_objects(cmd, crate_type, codegen_results);
// OBJECT-FILES-YES
add_local_crate_allocator_objects(cmd, codegen_results);