Do not strip debuginfo by default for MSVC

Author: Kobzol

src/cargo/ops/cargo_compile/mod.rs

@@ -436,6 +436,7 @@ pub fn create_bcx<'a, 'gctx>(
         &units,
         &scrape_units,
         host_kind_requested.then_some(explicit_host_kind),
+        &target_data,
     );
 
     let mut extra_compiler_args = HashMap::new();
@@ -575,6 +576,7 @@ fn rebuild_unit_graph_shared(
     roots: &[Unit],
     scrape_units: &[Unit],
     to_host: Option<CompileKind>,
+    target_data: &RustcTargetData<'_>,
 ) -> (Vec<Unit>, Vec<Unit>, UnitGraph) {
     let mut result = UnitGraph::new();
     // Map of the old unit to the new unit, used to avoid recursing into units
@@ -591,6 +593,7 @@ fn rebuild_unit_graph_shared(
                 root,
                 false,
                 to_host,
+                target_data,
             )
         })
         .collect();
@@ -617,6 +620,7 @@ fn traverse_and_share(
     unit: &Unit,
     unit_is_for_host: bool,
     to_host: Option<CompileKind>,
+    target_data: &RustcTargetData<'_>,
 ) -> Unit {
     if let Some(new_unit) = memo.get(unit) {
         // Already computed, no need to recompute.
@@ -634,6 +638,7 @@ fn traverse_and_share(
                 &dep.unit,
                 dep.unit_for.is_for_host(),
                 to_host,
+                target_data,
             );
             new_dep_unit.hash(&mut dep_hash);
             UnitDep {
@@ -657,8 +662,13 @@ fn traverse_and_share(
         _ => unit.kind,
     };
 
+    let is_target_windows_msvc = target_data
+        .short_name(&unit.kind)
+        .ends_with("-pc-windows-msvc");
     let mut profile = unit.profile.clone();
-    if profile.strip.is_deferred() {
+    // For MSVC, rustc currently treats -Cstrip=debuginfo same as -Cstrip=symbols, which causes
+    // this optimization to also remove symbols and thus break backtraces.
+    if profile.strip.is_deferred() && !is_target_windows_msvc {
         // If strip was not manually set, and all dependencies of this unit together
         // with this unit have debuginfo turned off, we enable debuginfo stripping.
         // This will remove pre-existing debug symbols coming from the standard library.