Rollup merge of #87320 - danakj:debug-compilation-dir, r=michaelwoerister

Introduce -Z remap-cwd-prefix switch

This switch remaps any absolute paths rooted under the current
working directory to a new value. This includes remapping the
debug info in `DW_AT_comp_dir` and `DW_AT_decl_file`.

Importantly, this flag does not require passing the current working
directory to the compiler, such that the command line can be
run on any machine (with the same input files) and produce the
same results. This is critical property for debugging compiler
issues that crop up on remote machines.

This is based on adetaylor's https://github.com/rust-lang/rust/commit/dbc4ae7cba0ba8d650b91ddd459b86a02a2d05c5

Major Change Proposal: https://github.com/rust-lang/compiler-team/issues/450
Discussed on #38322. Would resolve issue #87325.

5 files changed, 102 insertions, 5 deletions

diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 81433e57102..cfe13b1fd4e 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -754,6 +754,7 @@ 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);
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index fdedb7e6a4a..32aa035e1cd 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/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);
 
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index bb29a87035e..8110afe75fa 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1250,6 +1250,8 @@ 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"),
diff --git a/src/doc/unstable-book/src/compiler-flags/remap-cwd-prefix.md b/src/doc/unstable-book/src/compiler-flags/remap-cwd-prefix.md
new file mode 100644
index 00000000000..977d258529f
--- /dev/null
+++ b/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
+```
diff --git a/src/test/run-make-fulldeps/reproducible-build/Makefile b/src/test/run-make-fulldeps/reproducible-build/Makefile
index a17ec212cfd..adccc153568 100644
--- a/src/test/run-make-fulldeps/reproducible-build/Makefile
+++ b/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