From 53c4e0c19ac220085638e856999639fe26cb2a00 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 17 Mar 2020 19:10:56 -0700 Subject: [PATCH] Implement -Zlink-native-libraries This implements a flag `-Zlink-native-libraries=yes/no`. If set to true/yes, or unspecified, then native libraries referenced via `#[link]` attributes will be put on the linker line (ie, unchanged behaviour). If `-Zlink-native-libraries=no` is specified then rustc will not add the native libraries to the link line. The assumption is that the outer build system driving the build already knows about the native libraries and will specify them to the linker directly (for example via `-Clink-arg=`). Addresses issue #70093 --- src/librustc_codegen_ssa/back/link.rs | 13 ++++++++++--- src/librustc_session/options.rs | 2 ++ src/test/ui/issues/issue-70093.rs | 8 ++++++++ 3 files changed, 20 insertions(+), 3 deletions(-) create mode 100644 src/test/ui/issues/issue-70093.rs diff --git a/src/librustc_codegen_ssa/back/link.rs b/src/librustc_codegen_ssa/back/link.rs index 672b6e4aa46..613833b7202 100644 --- a/src/librustc_codegen_ssa/back/link.rs +++ b/src/librustc_codegen_ssa/back/link.rs @@ -1379,10 +1379,17 @@ fn link_args<'a, B: ArchiveBuilder<'a>>( // link line. And finally upstream native libraries can't depend on anything // in this DAG so far because they're only dylibs and dylibs can only depend // on other dylibs (e.g., other native deps). - add_local_native_libraries(cmd, sess, codegen_results); + // + // If -Zlink-native-libraries=false is set, then the assumption is that an + // external build system already has the native dependencies defined, and it + // will provide them to the linker itself. + if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) { + add_local_native_libraries(cmd, sess, codegen_results); + } add_upstream_rust_crates::(cmd, sess, codegen_results, crate_type, tmpdir); - add_upstream_native_libraries(cmd, sess, codegen_results, crate_type); - + if sess.opts.debugging_opts.link_native_libraries.unwrap_or(true) { + add_upstream_native_libraries(cmd, sess, codegen_results, crate_type); + } // Tell the linker what we're doing. if crate_type != config::CrateType::Executable { cmd.build_dylib(out_filename); diff --git a/src/librustc_session/options.rs b/src/librustc_session/options.rs index 72c720d09b0..775259911c1 100644 --- a/src/librustc_session/options.rs +++ b/src/librustc_session/options.rs @@ -959,4 +959,6 @@ fn parse_symbol_mangling_version( "link the `.rlink` file generated by `-Z no-link`"), new_llvm_pass_manager: Option = (None, parse_opt_bool, [TRACKED], "use new LLVM pass manager"), + link_native_libraries: Option = (None, parse_opt_bool, [UNTRACKED], + "Link native libraries in the linker invocation."), } diff --git a/src/test/ui/issues/issue-70093.rs b/src/test/ui/issues/issue-70093.rs new file mode 100644 index 00000000000..95ab86ebcb1 --- /dev/null +++ b/src/test/ui/issues/issue-70093.rs @@ -0,0 +1,8 @@ +// run-pass +// compile-flags: -Zlink-native-libraries=no -Cdefault-linker-libraries=yes +// ignore-windows - this will probably only work on unixish systems + +#[link(name = "some-random-non-existent-library", kind = "static")] +extern "C" {} + +fn main() {}