From 76103a8f6e838ca5bd9cf16b6236519c7c78e81d Mon Sep 17 00:00:00 2001
From: Zalathar <Zalathar@users.noreply.github.com>
Date: Thu, 2 Nov 2023 17:34:05 +1100
Subject: [PATCH] Remove support for alias `-Z symbol-mangling-version`

---
 compiler/rustc_interface/src/tests.rs         |  1 -
 compiler/rustc_session/src/config.rs          | 33 +++++++------------
 compiler/rustc_session/src/options.rs         |  3 --
 .../crate-hash-rustc-version/Makefile         |  2 +-
 4 files changed, 13 insertions(+), 26 deletions(-)

diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 594283168c98d..8e66083a390fc 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -817,7 +817,6 @@ fn test_unstable_options_tracking_hash() {
     tracked!(split_lto_unit, Some(true));
     tracked!(src_hash_algorithm, Some(SourceFileHashAlgorithm::Sha1));
     tracked!(stack_protector, StackProtector::All);
-    tracked!(symbol_mangling_version, Some(SymbolManglingVersion::V0));
     tracked!(teach, true);
     tracked!(thinlto, Some(true));
     tracked!(thir_unsafeck, true);
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index a8ebab4ae333c..715a7f9cb631b 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -2674,28 +2674,19 @@ pub fn build_session_options(
         );
     }
 
-    // Handle both `-Z symbol-mangling-version` and `-C symbol-mangling-version`; the latter takes
-    // precedence.
-    match (cg.symbol_mangling_version, unstable_opts.symbol_mangling_version) {
-        (Some(smv_c), Some(smv_z)) if smv_c != smv_z => {
-            handler.early_error(
-                "incompatible values passed for `-C symbol-mangling-version` \
-                and `-Z symbol-mangling-version`",
-            );
-        }
-        (Some(SymbolManglingVersion::V0), _) => {}
-        (Some(_), _) if !unstable_opts.unstable_options => {
-            handler
-                .early_error("`-C symbol-mangling-version=legacy` requires `-Z unstable-options`");
-        }
-        (None, None) => {}
-        (None, smv) => {
-            handler.early_warn(
-                "`-Z symbol-mangling-version` is deprecated; use `-C symbol-mangling-version`",
-            );
-            cg.symbol_mangling_version = smv;
+    // Check for unstable values of `-C symbol-mangling-version`.
+    // This is what prevents them from being used on stable compilers.
+    match cg.symbol_mangling_version {
+        // Stable values:
+        None | Some(SymbolManglingVersion::V0) => {}
+        // Unstable values:
+        Some(SymbolManglingVersion::Legacy) => {
+            if !unstable_opts.unstable_options {
+                handler.early_error(
+                    "`-C symbol-mangling-version=legacy` requires `-Z unstable-options`",
+                );
+            }
         }
-        _ => {}
     }
 
     // Check for unstable values of `-C instrument-coverage`.
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 30c8b9d67002c..8669c37e35a4e 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1823,9 +1823,6 @@ written to standard error output)"),
         "control if mem::uninitialized and mem::zeroed panic on more UB"),
     strip: Strip = (Strip::None, parse_strip, [UNTRACKED],
         "tell the linker which information to strip (`none` (default), `debuginfo` or `symbols`)"),
-    symbol_mangling_version: Option<SymbolManglingVersion> = (None,
-        parse_symbol_mangling_version, [TRACKED],
-        "which mangling version to use for symbol names ('legacy' (default) or 'v0')"),
     #[rustc_lint_opt_deny_field_access("use `Session::teach` instead of this field")]
     teach: bool = (false, parse_bool, [TRACKED],
         "show extended diagnostic help (default: no)"),
diff --git a/tests/run-make/crate-hash-rustc-version/Makefile b/tests/run-make/crate-hash-rustc-version/Makefile
index f1d2a36041045..6bf504bf01be5 100644
--- a/tests/run-make/crate-hash-rustc-version/Makefile
+++ b/tests/run-make/crate-hash-rustc-version/Makefile
@@ -4,7 +4,7 @@ include ../tools.mk
 # Ensure that crates compiled with different rustc versions cannot
 # be dynamically linked.
 
-FLAGS := -Cprefer-dynamic -Zsymbol-mangling-version=v0
+FLAGS := -Cprefer-dynamic -Csymbol-mangling-version=v0
 UNAME := $(shell uname)
 ifeq ($(UNAME),Linux)
   EXT=".so"