Infer the path of toolchain binaries from the linker path

Author: bjorn3

src/archive.rs

@@ -220,8 +220,10 @@ impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
         std::mem::drop(builder);
 
         if self.update_symbols {
+            let ranlib = crate::toolchain::get_toolchain_binary(self.config.sess, "ranlib");
+
             // Run ranlib to be able to link the archive
-            let status = std::process::Command::new("ranlib")
+            let status = std::process::Command::new(ranlib)
                 .arg(self.config.dst)
                 .status()
                 .expect("Couldn't run ranlib");

src/driver/aot.rs

@@ -277,6 +277,9 @@ fn codegen_global_asm(tcx: TyCtxt<'_>, cgu_name: &str, global_asm: &str) {
         return;
     }
 
+    let assembler = crate::toolchain::get_toolchain_binary(tcx.sess, "as");
+    let linker = crate::toolchain::get_toolchain_binary(tcx.sess, "ld");
+
     // Remove all LLVM style comments
     let global_asm = global_asm.lines().map(|line| {
         if let Some(index) = line.find("//") {
@@ -292,7 +295,7 @@ fn codegen_global_asm(tcx: TyCtxt<'_>, cgu_name: &str, global_asm: &str) {
 
     // Assemble `global_asm`
     let global_asm_object_file = add_file_stem_postfix(output_object_file.clone(), ".asm");
-    let mut child = Command::new("as")
+    let mut child = Command::new(assembler)
         .arg("-o").arg(&global_asm_object_file)
         .stdin(Stdio::piped())
         .spawn()
@@ -306,7 +309,7 @@ fn codegen_global_asm(tcx: TyCtxt<'_>, cgu_name: &str, global_asm: &str) {
     // Link the global asm and main object file together
     let main_object_file = add_file_stem_postfix(output_object_file.clone(), ".main");
     std::fs::rename(&output_object_file, &main_object_file).unwrap();
-    let status = Command::new("ld")
+    let status = Command::new(linker)
         .arg("-r") // Create a new object file
         .arg("-o").arg(output_object_file)
         .arg(&main_object_file)

src/lib.rs

@@ -64,6 +64,7 @@ mod optimize;
 mod pointer;
 mod pretty_clif;
 mod target_features_whitelist;
+mod toolchain;
 mod trap;
 mod unsize;
 mod value_and_place;

src/toolchain.rs

@@ -0,0 +1,115 @@
+use std::path::PathBuf;
+
+use rustc_middle::bug;
+use rustc_session::Session;
+use rustc_target::spec::LinkerFlavor;
+
+/// Tries to infer the path of a binary for the target toolchain from the linker name.
+pub(crate) fn get_toolchain_binary(sess: &Session, tool: &str) -> PathBuf {
+    let (mut linker, _linker_flavor) = linker_and_flavor(sess);
+    let linker_file_name = linker.file_name().and_then(|name| name.to_str()).unwrap_or_else(|| {
+        sess.fatal("couldn't extract file name from specified linker")
+    });
+
+    if linker_file_name == "ld.lld" {
+        if tool != "ld" {
+            linker.set_file_name(tool)
+        }
+    } else {
+        let tool_file_name = linker_file_name
+            .replace("ld", tool)
+            .replace("gcc", tool)
+            .replace("clang", tool)
+            .replace("cc", tool);
+
+        linker.set_file_name(tool_file_name)
+    }
+
+    linker
+}
+
+// Adapted from https://github.com/rust-lang/rust/blob/5db778affee7c6600c8e7a177c48282dab3f6292/src/librustc_codegen_ssa/back/link.rs#L848-L931
+fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
+    fn infer_from(
+        sess: &Session,
+        linker: Option<PathBuf>,
+        flavor: Option<LinkerFlavor>,
+    ) -> Option<(PathBuf, LinkerFlavor)> {
+        match (linker, flavor) {
+            (Some(linker), Some(flavor)) => Some((linker, flavor)),
+            // only the linker flavor is known; use the default linker for the selected flavor
+            (None, Some(flavor)) => Some((
+                PathBuf::from(match flavor {
+                    LinkerFlavor::Em => {
+                        if cfg!(windows) {
+                            "emcc.bat"
+                        } else {
+                            "emcc"
+                        }
+                    }
+                    LinkerFlavor::Gcc => {
+                        if cfg!(any(target_os = "solaris", target_os = "illumos")) {
+                            // On historical Solaris systems, "cc" may have
+                            // been Sun Studio, which is not flag-compatible
+                            // with "gcc".  This history casts a long shadow,
+                            // and many modern illumos distributions today
+                            // ship GCC as "gcc" without also making it
+                            // available as "cc".
+                            "gcc"
+                        } else {
+                            "cc"
+                        }
+                    }
+                    LinkerFlavor::Ld => "ld",
+                    LinkerFlavor::Msvc => "link.exe",
+                    LinkerFlavor::Lld(_) => "lld",
+                    LinkerFlavor::PtxLinker => "rust-ptx-linker",
+                }),
+                flavor,
+            )),
+            (Some(linker), None) => {
+                let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
+                    sess.fatal("couldn't extract file stem from specified linker")
+                });
+
+                let flavor = if stem == "emcc" {
+                    LinkerFlavor::Em
+                } else if stem == "gcc"
+                    || stem.ends_with("-gcc")
+                    || stem == "clang"
+                    || stem.ends_with("-clang")
+                {
+                    LinkerFlavor::Gcc
+                } else if stem == "ld" || stem == "ld.lld" || stem.ends_with("-ld") {
+                    LinkerFlavor::Ld
+                } else if stem == "link" || stem == "lld-link" {
+                    LinkerFlavor::Msvc
+                } else if stem == "lld" || stem == "rust-lld" {
+                    LinkerFlavor::Lld(sess.target.target.options.lld_flavor)
+                } else {
+                    // fall back to the value in the target spec
+                    sess.target.target.linker_flavor
+                };
+
+                Some((linker, flavor))
+            }
+            (None, None) => None,
+        }
+    }
+
+    // linker and linker flavor specified via command line have precedence over what the target
+    // specification specifies
+    if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), sess.opts.cg.linker_flavor) {
+        return ret;
+    }
+
+    if let Some(ret) = infer_from(
+        sess,
+        sess.target.target.options.linker.clone().map(PathBuf::from),
+        Some(sess.target.target.linker_flavor),
+    ) {
+        return ret;
+    }
+
+    bug!("Not enough information provided to determine how to invoke the linker");
+}