Rollup merge of #89920 - hudson-ayers:location-detail-control, r=davidtwco

Implement -Z location-detail flag

This PR implements the `-Z location-detail` flag as described in https://github.com/rust-lang/rfcs/pull/2091 .

`-Z location-detail=val` controls what location details are tracked when using `caller_location`. This allows users to control what location details are printed as part of panic messages, by allowing them to exclude any combination of filenames, line numbers, and column numbers. This option is intended to provide users with a way to mitigate the size impact of `#[track_caller]`.

Some measurements of the savings of this approach on an embedded binary can be found here: https://github.com/rust-lang/rust/issues/70579#issuecomment-942556822 .

Closes #70580 (unless people want to leave that open as a place for discussion of further improvements).

This is my first real PR to rust, so any help correcting mistakes / understanding side effects / improving my tests is appreciated :)

I have one question: RFC 2091 specified this as a debugging option (I think that is what -Z implies?). Does that mean this can never be stabilized without a separate MCP? If so, do I need to submit an MCP now, or is the initial RFC specifying this option sufficient for this to be merged as is, and then an MCP would be needed for eventual stabilization?

4 files changed, 55 insertions, 6 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs b/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
index d4cbba18029..b5e97ec8fe0 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
@@ -80,10 +80,17 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         line: u32,
         col: u32,
     ) -> MPlaceTy<'tcx, M::PointerTag> {
-        let file =
-            self.allocate_str(&filename.as_str(), MemoryKind::CallerLocation, Mutability::Not);
-        let line = Scalar::from_u32(line);
-        let col = Scalar::from_u32(col);
+        let loc_details = &self.tcx.sess.opts.debugging_opts.location_detail;
+        let file = if loc_details.file {
+            self.allocate_str(&filename.as_str(), MemoryKind::CallerLocation, Mutability::Not)
+        } else {
+            // FIXME: This creates a new allocation each time. It might be preferable to
+            // perform this allocation only once, and re-use the `MPlaceTy`.
+            // See https://github.com/rust-lang/rust/pull/89920#discussion_r730012398
+            self.allocate_str("<redacted>", MemoryKind::CallerLocation, Mutability::Not)
+        };
+        let line = if loc_details.line { Scalar::from_u32(line) } else { Scalar::from_u32(0) };
+        let col = if loc_details.column { Scalar::from_u32(col) } else { Scalar::from_u32(0) };
 
         // Allocate memory for `CallerLocation` struct.
         let loc_ty = self
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 844e5ab56a4..dab4d485e2d 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -5,7 +5,9 @@ use rustc_errors::{emitter::HumanReadableErrorType, registry, ColorConfig};
 use rustc_session::config::InstrumentCoverage;
 use rustc_session::config::Strip;
 use rustc_session::config::{build_configuration, build_session_options, to_crate_config};
-use rustc_session::config::{rustc_optgroups, ErrorOutputType, ExternLocation, Options, Passes};
+use rustc_session::config::{
+    rustc_optgroups, ErrorOutputType, ExternLocation, LocationDetail, Options, Passes,
+};
 use rustc_session::config::{CFGuard, ExternEntry, LinkerPluginLto, LtoCli, SwitchWithOptPath};
 use rustc_session::config::{
     Externs, OutputType, OutputTypes, SymbolManglingVersion, WasiExecModel,
@@ -733,6 +735,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(instrument_mcount, true);
     tracked!(link_only, true);
     tracked!(llvm_plugins, vec![String::from("plugin_name")]);
+    tracked!(location_detail, LocationDetail { file: true, line: false, column: false });
     tracked!(merge_functions, Some(MergeFunctions::Disabled));
     tracked!(mir_emit_retag, true);
     tracked!(mir_opt_level, Some(4));
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index ac4bce7350b..299dfed9d5d 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -174,6 +174,20 @@ impl LinkerPluginLto {
     }
 }
 
+/// The different settings that can be enabled via the `-Z location-detail` flag.
+#[derive(Clone, PartialEq, Hash, Debug)]
+pub struct LocationDetail {
+    pub file: bool,
+    pub line: bool,
+    pub column: bool,
+}
+
+impl LocationDetail {
+    pub fn all() -> Self {
+        Self { file: true, line: true, column: true }
+    }
+}
+
 #[derive(Clone, PartialEq, Hash, Debug)]
 pub enum SwitchWithOptPath {
     Enabled(Option<PathBuf>),
@@ -2422,7 +2436,7 @@ crate mod dep_tracking {
     use super::LdImpl;
     use super::{
         CFGuard, CrateType, DebugInfo, ErrorOutputType, InstrumentCoverage, LinkerPluginLto,
-        LtoCli, OptLevel, OutputType, OutputTypes, Passes, SourceFileHashAlgorithm,
+        LocationDetail, LtoCli, OptLevel, OutputType, OutputTypes, Passes, SourceFileHashAlgorithm,
         SwitchWithOptPath, SymbolManglingVersion, TrimmedDefPaths,
     };
     use crate::lint;
@@ -2513,6 +2527,7 @@ crate mod dep_tracking {
         Option<LdImpl>,
         OutputType,
         RealFileName,
+        LocationDetail,
     );
 
     impl<T1, T2> DepTrackingHash for (T1, T2)
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 059b5dc5175..782055b9a77 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -368,6 +368,8 @@ mod desc {
         "either a boolean (`yes`, `no`, `on`, `off`, etc), `thin`, `fat`, or omitted";
     pub const parse_linker_plugin_lto: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), or the path to the linker plugin";
+    pub const parse_location_detail: &str =
+        "comma seperated list of location details to track: `file`, `line`, or `column`";
     pub const parse_switch_with_opt_path: &str =
         "an optional path to the profiling data output directory";
     pub const parse_merge_functions: &str = "one of: `disabled`, `trampolines`, or `aliases`";
@@ -484,6 +486,25 @@ mod parse {
         }
     }
 
+    crate fn parse_location_detail(ld: &mut LocationDetail, v: Option<&str>) -> bool {
+        if let Some(v) = v {
+            ld.line = false;
+            ld.file = false;
+            ld.column = false;
+            for s in v.split(',') {
+                match s {
+                    "file" => ld.file = true,
+                    "line" => ld.line = true,
+                    "column" => ld.column = true,
+                    _ => return false,
+                }
+            }
+            true
+        } else {
+            false
+        }
+    }
+
     crate fn parse_opt_comma_list(slot: &mut Option<Vec<String>>, v: Option<&str>) -> bool {
         match v {
             Some(s) => {
@@ -1152,6 +1173,9 @@ options! {
         "a list LLVM plugins to enable (space separated)"),
     llvm_time_trace: bool = (false, parse_bool, [UNTRACKED],
         "generate JSON tracing data file from LLVM data (default: no)"),
+    location_detail: LocationDetail = (LocationDetail::all(), parse_location_detail, [TRACKED],
+        "comma seperated list of location details to be tracked when using caller_location \
+        valid options are `file`, `line`, and `column` (default: all)"),
     ls: bool = (false, parse_bool, [UNTRACKED],
         "list the symbols defined by a library crate (default: no)"),
     macro_backtrace: bool = (false, parse_bool, [UNTRACKED],