From c1f1f60bcbb7a0f4021e8aa1b6fa7113f2c6d27a Mon Sep 17 00:00:00 2001
From: gftea <1705787+gftea@users.noreply.github.com>
Date: Tue, 20 Dec 2022 14:45:19 +0100
Subject: [PATCH] Update instrument-coverage.md

Document the default for LLVM_PROFILE_FILE and add a recemmondation for setting
it for older versions of Rust which had a different default.
---
 src/doc/rustc/src/instrument-coverage.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/doc/rustc/src/instrument-coverage.md b/src/doc/rustc/src/instrument-coverage.md
index 38fd5c9699763..da91e25595cc7 100644
--- a/src/doc/rustc/src/instrument-coverage.md
+++ b/src/doc/rustc/src/instrument-coverage.md
@@ -201,6 +201,8 @@ $ RUSTFLAGS="-C instrument-coverage" \
     cargo test --tests
 ```
 
+> **Note**: The default for `LLVM_PROFILE_FILE` is `default_%m_%p.profraw`. Versions prior to 1.65 had a default of `default.profraw`, so if using those earlier versions, it is recommended to explicitly set `LLVM_PROFILE_FILE="default_%m_%p.profraw"` to avoid having multiple tests overwrite the `.profraw` files.
+
 Make note of the test binary file paths, displayed after the word "`Running`" in the test output:
 
 ```text