Introduce -Z remap-cwd-prefix switch

compiler/rustc_interface/src/tests.rs

@@ -753,6 +753,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(profiler_runtime, "abc".to_string());
     tracked!(relax_elf_relocations, Some(true));
     tracked!(relro_level, Some(RelroLevel::Full));
+    tracked!(remap_cwd_prefix, Some(PathBuf::from("abc")));
     tracked!(simulate_remapped_rust_src_base, Some(PathBuf::from("/rustc/abc")));
     tracked!(report_delayed_bugs, true);
     tracked!(sanitizer, SanitizerSet::ADDRESS);

compiler/rustc_session/src/config.rs

@@ -1920,9 +1920,10 @@ fn parse_extern_dep_specs(
 
 fn parse_remap_path_prefix(
     matches: &getopts::Matches,
+    debugging_opts: &DebuggingOptions,
     error_format: ErrorOutputType,
 ) -> Vec<(PathBuf, PathBuf)> {
-    matches
+    let mut mapping: Vec<(PathBuf, PathBuf)> = matches
         .opt_strs("remap-path-prefix")
         .into_iter()
         .map(|remap| match remap.rsplit_once('=') {
@@ -1932,7 +1933,15 @@ fn parse_remap_path_prefix(
             ),
             Some((from, to)) => (PathBuf::from(from), PathBuf::from(to)),
         })
-        .collect()
+        .collect();
+    match &debugging_opts.remap_cwd_prefix {
+        Some(to) => match std::env::current_dir() {
+            Ok(cwd) => mapping.push((cwd, to.clone())),
+            Err(_) => (),
+        },
+        None => (),
+    };
+    mapping
 }
 
 pub fn build_session_options(matches: &getopts::Matches) -> Options {
@@ -2077,7 +2086,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
 
     let crate_name = matches.opt_str("crate-name");
 
-    let remap_path_prefix = parse_remap_path_prefix(matches, error_format);
+    let remap_path_prefix = parse_remap_path_prefix(matches, &debugging_opts, error_format);
 
     let pretty = parse_pretty(&debugging_opts, error_format);
 

compiler/rustc_session/src/options.rs

@@ -1236,6 +1236,8 @@ options! {
         "whether ELF relocations can be relaxed"),
     relro_level: Option<RelroLevel> = (None, parse_relro_level, [TRACKED],
         "choose which RELRO level to use"),
+    remap_cwd_prefix: Option<PathBuf> = (None, parse_opt_pathbuf, [TRACKED],
+        "remap paths under the current working directory to this path prefix"),
     simulate_remapped_rust_src_base: Option<PathBuf> = (None, parse_opt_pathbuf, [TRACKED],
         "simulate the effect of remap-debuginfo = true at bootstrapping by remapping path \
         to rust's source base directory. only meant for testing purposes"),

src/doc/unstable-book/src/compiler-flags/remap-cwd-prefix.md

@@ -0,0 +1,24 @@
+# `remap-cwd-prefix`
+
+The tracking issue for this feature is: [#87325](https://github.com/rust-lang/rust/issues/87325).
+
+------------------------
+
+This flag will rewrite absolute paths under the current working directory,
+replacing the current working directory prefix with a specified value.
+
+The given value may be absolute or relative, or empty. This switch takes
+precidence over `--remap-path-prefix` in case they would both match a given
+path.
+
+This flag helps to produce deterministic output, by removing the current working
+directory from build output, while allowing the command line to be universally
+reproducible, such that the same execution will work on all machines, regardless
+of build environment.
+
+## Example
+```sh
+# This would produce an absolute path to main.rs in build outputs of
+# "./main.rs".
+rustc -Z remap-cwd-prefix=. main.rs
+```

src/test/run-make-fulldeps/reproducible-build/Makefile

@@ -9,9 +9,19 @@ all:  \
 	opt \
 	link_paths \
 	remap_paths \
-	different_source_dirs \
+	different_source_dirs_rlib \
+	remap_cwd_rlib \
+	remap_cwd_to_empty \
 	extern_flags
 
+# TODO: Builds of `bin` crate types are not deterministic with debuginfo=2 on
+# Windows.
+# See: https://github.com/rust-lang/rust/pull/87320#issuecomment-920105533
+# Issue: https://github.com/rust-lang/rust/issues/88982
+#
+#	different_source_dirs_bin \
+#	remap_cwd_bin \
+
 smoke:
 	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
 	$(RUSTC) linker.rs -O
@@ -52,7 +62,19 @@ remap_paths:
 	$(RUSTC) reproducible-build.rs --crate-type rlib --remap-path-prefix=/b=/c
 	cmp "$(TMPDIR)/libreproducible_build.rlib" "$(TMPDIR)/libfoo.rlib" || exit 1
 
-different_source_dirs:
+different_source_dirs_bin:
+	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
+	$(RUSTC) reproducible-build-aux.rs
+	mkdir $(TMPDIR)/test
+	cp reproducible-build.rs $(TMPDIR)/test
+	$(RUSTC) reproducible-build.rs --crate-type bin --remap-path-prefix=$$PWD=/b
+	cp $(TMPDIR)/reproducible-build $(TMPDIR)/foo
+	(cd $(TMPDIR)/test && $(RUSTC) reproducible-build.rs \
+		--remap-path-prefix=$(TMPDIR)/test=/b \
+		--crate-type bin)
+	cmp "$(TMPDIR)/reproducible-build" "$(TMPDIR)/foo" || exit 1
+
+different_source_dirs_rlib:
 	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
 	$(RUSTC) reproducible-build-aux.rs
 	mkdir $(TMPDIR)/test
@@ -64,6 +86,45 @@ different_source_dirs:
 		--crate-type rlib)
 	cmp "$(TMPDIR)/libreproducible_build.rlib" "$(TMPDIR)/libfoo.rlib" || exit 1
 
+remap_cwd_bin:
+	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
+	$(RUSTC) reproducible-build-aux.rs
+	mkdir $(TMPDIR)/test
+	cp reproducible-build.rs $(TMPDIR)/test
+	$(RUSTC) reproducible-build.rs --crate-type bin -C debuginfo=2 \
+	  -Z remap-cwd-prefix=.
+	cp $(TMPDIR)/reproducible-build $(TMPDIR)/first
+	(cd $(TMPDIR)/test && \
+	 $(RUSTC) reproducible-build.rs --crate-type bin -C debuginfo=2 \
+	   -Z remap-cwd-prefix=.)
+	cmp "$(TMPDIR)/first" "$(TMPDIR)/reproducible-build" || exit 1
+
+remap_cwd_rlib:
+	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
+	$(RUSTC) reproducible-build-aux.rs
+	mkdir $(TMPDIR)/test
+	cp reproducible-build.rs $(TMPDIR)/test
+	$(RUSTC) reproducible-build.rs --crate-type rlib -C debuginfo=2 \
+	  -Z remap-cwd-prefix=.
+	cp $(TMPDIR)/libreproducible_build.rlib $(TMPDIR)/libfirst.rlib
+	(cd $(TMPDIR)/test && \
+	 $(RUSTC) reproducible-build.rs --crate-type rlib -C debuginfo=2 \
+	   -Z remap-cwd-prefix=.)
+	cmp "$(TMPDIR)/libfirst.rlib" "$(TMPDIR)/libreproducible_build.rlib" || exit 1
+
+remap_cwd_to_empty:
+	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
+	$(RUSTC) reproducible-build-aux.rs
+	mkdir $(TMPDIR)/test
+	cp reproducible-build.rs $(TMPDIR)/test
+	$(RUSTC) reproducible-build.rs --crate-type rlib -C debuginfo=2 \
+	  -Z remap-cwd-prefix=
+	cp $(TMPDIR)/libreproducible_build.rlib $(TMPDIR)/libfirst.rlib
+	(cd $(TMPDIR)/test && \
+	 $(RUSTC) reproducible-build.rs --crate-type rlib -C debuginfo=2 \
+	   -Z remap-cwd-prefix=)
+	cmp "$(TMPDIR)/libfirst.rlib" "$(TMPDIR)/libreproducible_build.rlib" || exit 1
+
 extern_flags:
 	rm -rf $(TMPDIR) && mkdir $(TMPDIR)
 	$(RUSTC) reproducible-build-aux.rs