Add -Z simulate-remapped-rust-src-base option to simulate path virutalisation during bootstrapping

compiler/rustc_interface/src/tests.rs

@@ -595,6 +595,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(profile_emit, Some(PathBuf::from("abc")));
     tracked!(relax_elf_relocations, Some(true));
     tracked!(relro_level, Some(RelroLevel::Full));
+    tracked!(simulate_remapped_rust_src_base, Some(PathBuf::from("/rustc/abc")));
     tracked!(report_delayed_bugs, true);
     tracked!(sanitizer, SanitizerSet::ADDRESS);
     tracked!(sanitizer_memory_track_origins, 2);

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1707,6 +1707,31 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
                         ..
                     } = source_file_to_import;
 
+                    // If this file is under $sysroot/lib/rustlib/src/ but has not been remapped
+                    // during rust bootstrapping by `remap-debuginfo = true`, and the user
+                    // wish to simulate that behaviour by -Z simulate-remapped-rust-src-base,
+                    // then we change `name` to a similar state as if the rust was bootstrapped
+                    // with `remap-debuginfo = true`.
+                    // This is useful for testing so that tests about the effects of
+                    // `try_to_translate_virtual_to_real` don't have to worry about how the
+                    // compiler is bootstrapped.
+                    if let Some(virtual_dir) =
+                        &sess.opts.debugging_opts.simulate_remapped_rust_src_base
+                    {
+                        if let Some(real_dir) = &sess.opts.real_rust_source_base_dir {
+                            if let rustc_span::FileName::Real(ref mut old_name) = name {
+                                if let rustc_span::RealFileName::LocalPath(local) = old_name {
+                                    if let Ok(rest) = local.strip_prefix(real_dir) {
+                                        *old_name = rustc_span::RealFileName::Remapped {
+                                            local_path: None,
+                                            virtual_name: virtual_dir.join(rest),
+                                        };
+                                    }
+                                }
+                            }
+                        }
+                    }
+
                     // If this file's path has been remapped to `/rustc/$hash`,
                     // we might be able to reverse that (also see comments above,
                     // on `try_to_translate_virtual_to_real`).

compiler/rustc_session/src/options.rs

@@ -1161,6 +1161,9 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "whether ELF relocations can be relaxed"),
     relro_level: Option<RelroLevel> = (None, parse_relro_level, [TRACKED],
         "choose which RELRO level to use"),
+    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"),
     report_delayed_bugs: bool = (false, parse_bool, [TRACKED],
         "immediately print bugs registered with `delay_span_bug` (default: no)"),
     sanitizer: SanitizerSet = (SanitizerSet::empty(), parse_sanitizers, [TRACKED],

src/test/codegen/remap_path_prefix/issue-73167-remap-std.rs

@@ -1,10 +1,13 @@
 // ignore-windows
 
-// compile-flags: -g  -C no-prepopulate-passes --remap-path-prefix=/=/the/root/
+// compile-flags: -g  -C no-prepopulate-passes -Z simulate-remapped-rust-src-base=/rustc/xyz
 
-// Here we check that imported code from std has their path remapped
+// Here we check that importing std will not cause real path to std source files
+// to leak. If rustc was compiled with remap-debuginfo = true, this should be
+// true automatically. If paths to std library hasn't been remapped, we use the
+// above simulate-remapped-rust-src-base option to do it temporarily
 
-// CHECK: !DIFile(filename: "{{/the/root/.*/library/std/src/panic.rs}}"
+// CHECK: !DIFile(filename: "{{/rustc/.*/library/std/src/panic.rs}}"
 fn main() {
     std::thread::spawn(|| {
         println!("hello");