`-C split-debuginfo=packed` generates duplicate .dwp files for shared objects

[jyn514]

I tried this code:

./configure --set rust.split-debuginfo=packed
x build --stage 0 compiler

I expected to see this happen: rustc/cargo generate a large .dwp file for rustc_driver.so and a small .dwp file for rustc-main.

Instead, this happened: Both crates have duplicate .dwp files:

; ls -lh build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/*rustc*
-rwxrwxr-x 4 jyn jyn 310M Mar 18 09:47 build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/librustc_driver.so
-rw-rw-r-- 2 jyn jyn 254M Mar 18 09:47 build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/librustc_driver.so.dwp
-rwxrwxr-x 3 jyn jyn  20K Mar 18 09:47 build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/rustc-main
-rw-rw-r-- 2 jyn jyn 254M Mar 18 09:47 build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/rustc-main.dwp

Meta

beta is

rust/src/stage0.json

Lines 19 to 22 in bb8a0ff

	"compiler": {
	"date": "2023-03-07",
	"version": "beta"
	},

[jyn514]

Found while investigating #64405 and #104968.

[jyn514]

Windows does not have this bug.

PS C:\Users\jyn\src\rust2> ls .\build\host\stage0-rustc\x86_64-pc-windows-msvc\release\


    Directory: C:\Users\jyn\src\rust2\build\host\stage0-rustc\x86_64-pc-windows-msvc\release


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a----         4/29/2023  11:25 AM         112640 rustc-main.exe
-a----         4/29/2023  11:25 AM      128864768 rustc_driver.dll
-a----         4/29/2023  11:25 AM      282644480 rustc_driver.pdb
-a----         4/29/2023  11:25 AM        3608576 rustc_main.pdb

[jyn514]

I nominated this because I'd like to ship a split-debuginfo rustc-debug component (or similar) for Linux, but this is blocking the work because the size of the component would be too large until it's fixed.

[pnkfelix]

Assigning to @davidtwco for investigation.