From bb55741d1fca51901e4ff421715977d6f2a701ef 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 | 7 +++++++ 3 files changed, 19 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 a71fe4430388..f2637e601477 100644 --- a/src/librustc_codegen_ssa/back/link.rs +++ b/src/librustc_codegen_ssa/back/link.rs @@ -1380,10 +1380,17 @@ 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 a1ecf4e8528b..cc9a8ac098f6 100644 --- a/src/librustc_session/options.rs +++ b/src/librustc_session/options.rs @@ -968,4 +968,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options, "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 000000000000..2ac22c631ef9 --- /dev/null +++ b/src/test/ui/issues/issue-70093.rs @@ -0,0 +1,7 @@ +// run-pass +// compile-flags: -Zlink-native-libraries=no -Cdefault-linker-libraries=yes + +#[link(name = "some-random-non-existent-library", kind = "static")] +extern "C" {} + +fn main() {}