From 9e0746492d1e252eae29108c5dd9456ddc5b6e97 Mon Sep 17 00:00:00 2001
From: bors <bors@rust-lang.org>
Date: Thu, 26 Jan 2023 18:14:08 +0000
Subject: [PATCH] Auto merge of #11347 - kamirr:fix-split-debuginfo-windows,
 r=weihanglo

Fix split-debuginfo support detection

cargo assumed that if `-Csplit-debuginfo=packed` worked, all values would be correct. This however is not the case -- as of Rust 1.65.0, rustc supports `packed`, but not `unpacked` or `off` on Windows. Because of this, having `split-debuginfo="unpacked`" on Windows has caused builds to fail, as cargo assumed that the option is fine (`split-debuginfo=packed` worked), but rustc then failed when being passed `-Csplit-debuginfo=unpacked`.

Consider an empty project with the following change to `Cargo.toml`:
```toml
[profile.dev]
split-debuginfo="unpacked"
```
`cargo +1.64.0 build` will work, but `cargo +1.65.0 build` will fail with the following error message:

```
PS C:\REDACTED> cargo build
   Compiling tmp v0.1.0 (C:\REDACTED)
error: `-Csplit-debuginfo=unpacked` is unstable on this platform

error: could not compile `tmp` due to previous error
```

With this patch and 1.65.0 rustc, cargo will ignore all `split-debuginfo` settings, but with https://github.com/rust-lang/rust/pull/104104 rustc (approved, awaiting merge), it will properly detect supported values for `split-debuginfo` and only ignore those that are unsupported.
---
 src/cargo/core/compiler/build_context/target_info.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/cargo/core/compiler/build_context/target_info.rs b/src/cargo/core/compiler/build_context/target_info.rs
index 754adcf3c..298900f1b 100644
--- a/src/cargo/core/compiler/build_context/target_info.rs
+++ b/src/cargo/core/compiler/build_context/target_info.rs
@@ -168,6 +168,18 @@ impl TargetInfo {
         loop {
             let extra_fingerprint = kind.fingerprint_hash();
 
+            // Query rustc for supported -Csplit-debuginfo values
+            let support_split_debuginfo = rustc
+                .cached_output(
+                    rustc.workspace_process().arg("--print=split-debuginfo"),
+                    extra_fingerprint,
+                )
+                .unwrap_or_default()
+                .0
+                .lines()
+                .map(String::from)
+                .collect();
+
             // Query rustc for several kinds of info from each line of output:
             // 0) file-names (to determine output file prefix/suffix for given crate type)
             // 1) sysroot