don't show the full linker args unless --verbose is passed

the linker arguments can be *very* long, especially for crates with many dependencies. often they are not useful. omit them unless the user specifically requests them.

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -934,12 +934,12 @@ fn link_natively<'a>(
                 let mut output = prog.stderr.clone();
                 output.extend_from_slice(&prog.stdout);
                 let escaped_output = escape_linker_output(&output, flavor);
-                // FIXME: Add UI tests for this error.
                 let err = errors::LinkingFailed {
                     linker_path: &linker_path,
                     exit_status: prog.status,
                     command: &cmd,
                     escaped_output,
+                    verbose: sess.opts.verbose,
                 };
                 sess.dcx().emit_err(err);
                 // If MSVC's `link.exe` was expected but the return code

compiler/rustc_codegen_ssa/src/errors.rs

@@ -408,6 +408,7 @@ pub struct LinkingFailed<'a> {
     pub exit_status: ExitStatus,
     pub command: &'a Command,
     pub escaped_output: String,
+    pub verbose: bool,
 }
 
 impl IntoDiagnostic<'_> for LinkingFailed<'_> {
@@ -418,7 +419,13 @@ impl IntoDiagnostic<'_> for LinkingFailed<'_> {
 
         let contains_undefined_ref = self.escaped_output.contains("undefined reference to");
 
-        diag.note(format!("{:?}", self.command)).note(self.escaped_output);
+        if self.verbose {
+            diag.note(format!("{:?}", self.command));
+        } else {
+            diag.note("use `--verbose` to show all linker arguments");
+        }
+
+        diag.note(self.escaped_output);
 
         // Trying to match an error from OS linkers
         // which by now we have no way to translate.

tests/run-make/link-args-order/Makefile

@@ -6,5 +6,5 @@ RUSTC_FLAGS = -C linker-flavor=ld -C link-arg=a -C link-args="b c" -C link-args=
 RUSTC_FLAGS_PRE = -C linker-flavor=ld -Z pre-link-arg=a -Z pre-link-args="b c" -Z pre-link-args="d e" -Z pre-link-arg=f
 
 all:
-	$(RUSTC) $(RUSTC_FLAGS) empty.rs 2>&1 | $(CGREP) '"a" "b" "c" "d" "e" "f"'
-	$(RUSTC) $(RUSTC_FLAGS_PRE) empty.rs 2>&1 | $(CGREP) '"a" "b" "c" "d" "e" "f"'
+	$(RUSTC) $(RUSTC_FLAGS) empty.rs --print=link-args | $(CGREP) '"a" "b" "c" "d" "e" "f"'
+	$(RUSTC) $(RUSTC_FLAGS_PRE) empty.rs --print=link-args | $(CGREP) '"a" "b" "c" "d" "e" "f"'

tests/run-make/link-dedup/Makefile

@@ -6,7 +6,7 @@ all:
 	$(RUSTC) depa.rs
 	$(RUSTC) depb.rs
 	$(RUSTC) depc.rs
-	$(RUSTC) empty.rs --cfg bar 2>&1 | $(CGREP) '"-ltesta" "-ltestb" "-ltesta"'
-	$(RUSTC) empty.rs 2>&1 | $(CGREP) '"-ltesta"'
-	$(RUSTC) empty.rs 2>&1 | $(CGREP) -v '"-ltestb"'
-	$(RUSTC) empty.rs 2>&1 | $(CGREP) -v '"-ltesta" "-ltesta" "-ltesta"'
+	$(RUSTC) empty.rs --cfg bar --print=link-args | $(CGREP) '"-ltesta" "-ltestb" "-ltesta"'
+	$(RUSTC) empty.rs --print=link-args | $(CGREP) '"-ltesta"'
+	$(RUSTC) empty.rs --print=link-args | $(CGREP) -v '"-ltestb"'
+	$(RUSTC) empty.rs --print=link-args | $(CGREP) -v '"-ltesta" "-ltesta" "-ltesta"'

tests/run-make/linker-warning/Makefile

@@ -2,16 +2,24 @@ include ../tools.mk
 
 RUN_RUSTC := $(RUSTC_ORIGINAL) main.rs -o $(TMPDIR)/main -C linker=./fake-linker.sh
 
-all:
+all: succeeds_with_warnings errors linker_args
+
+succeeds_with_warnings:
 	# Run rustc with our fake linker, and make sure it shows warnings
 	$(RUN_RUSTC) -C link-arg=run_make_warn 2>&1 | $(CGREP) "warning: linker stderr: bar"
 
 	# Make sure it shows stdout, but only when --verbose is passed
 	$(RUN_RUSTC) -C link-arg=run_make_info --verbose 2>&1 | $(CGREP) "warning: linker stdout: foo"
 	$(RUN_RUSTC) -C link-arg=run_make_info 2>&1 | $(CGREP) -v "warning: linker stdout: foo"
 
+errors:
 	# Make sure we short-circuit this new path if the linker exits with an error (so the diagnostic is less verbose)
 	rm -f $(TMPDIR)/main
 	$(RUN_RUSTC) -C link-arg=run_make_error 2>&1 | $(CGREP) "note: error: baz"
 	! [ -e $(TMPDIR)/main ]
 
+linker_args:
+	# Make sure we don't show the linker args unless `--verbose` is passed
+	$(RUN_RUSTC) --verbose -C link-arg=run_make_error 2>&1 | $(CGREP) -e "PATH=.*fake-linker.sh.*run_make_error"
+	$(RUN_RUSTC) -C link-arg=run_make_error 2>&1 | $(CGREP) -v -e "PATH=.*fake-linker.sh.*run_make_error"
+