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Rollup merge of #66257 - mati865:long-section-names-no-more, r=alexcrichton

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Drop long-section-names linker workaround for windows-gnu

If we can trust objdump Rust doesn't emit sections loaded at runtime longer than 8 characters on windows-gnu (but still does on linux-gnu), debug sections are not affected by that limit.
I've ran tests and built few crates using exactly the same mingw-w64 version as Rusts CI just fine using **x86_64** toolchain.

The motivation for this change is making LLD work (it doesn't support `--enable-long-section-names`) with this target without hacks.

Bit of history:
The behaviour of LD changed in Binutils 2.20 released on 2009-10-16 and `--enable-long-section-names` was added to return to the old non conformant behaviour. Looking at the comment I can only guess there was a bug fixed in newer versions.

This workaround was added in https://github.com/rust-lang/rust/pull/13315 half a decade ago.
This commit is contained in:
Yuki Okushi 2019-11-12 16:36:07 +09:00 • committed by GitHub
commit 7596d34ea1
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27
src/librustc_target/spec/windows_base.rs
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@ -4,33 +4,6 @@ use std::default::Default;
pub fn opts() -> TargetOptions {
let mut pre_link_args = LinkArgs::new();
pre_link_args.insert(LinkerFlavor::Gcc, vec![
// And here, we see obscure linker flags #45. On windows, it has been
// found to be necessary to have this flag to compile liblibc.
//
// First a bit of background. On Windows, the file format is not ELF,
// but COFF (at least according to LLVM). COFF doesn't officially allow
// for section names over 8 characters, apparently. Our metadata
// section, ".note.rustc", you'll note is over 8 characters.
//
// On more recent versions of gcc on mingw, apparently the section name
// is *not* truncated, but rather stored elsewhere in a separate lookup
// table. On older versions of gcc, they apparently always truncated th
// section names (at least in some cases). Truncating the section name
// actually creates "invalid" objects [1] [2], but only for some
// introspection tools, not in terms of whether it can be loaded.
//
// Long story short, passing this flag forces the linker to *not*
// truncate section names (so we can find the metadata section after
// it's compiled). The real kicker is that rust compiled just fine on
// windows for quite a long time *without* this flag, so I have no idea
// why it suddenly started failing for liblibc. Regardless, we
// definitely don't want section name truncation, so we're keeping this
// flag for windows.
//
// [1] - https://sourceware.org/bugzilla/show_bug.cgi?id=13130
// [2] - https://code.google.com/p/go/issues/detail?id=2139
"-Wl,--enable-long-section-names".to_string(),
// Tell GCC to avoid linker plugins, because we are not bundling
// them with Windows installer, and Rust does its own LTO anyways.
"-fno-use-linker-plugin".to_string(),