Add run-make-fulldeps test

Implement RUSTC_FORCE_INCR_COMP_ARTIFACT_HEADER

Also makes minor docs edits.

12 files changed, 102 insertions, 31 deletions

diff --git a/compiler/rustc_span/src/def_id.rs b/compiler/rustc_span/src/def_id.rs
index fe5f70f4fd9..690afe1d458 100644
--- a/compiler/rustc_span/src/def_id.rs
+++ b/compiler/rustc_span/src/def_id.rs
@@ -126,14 +126,17 @@ impl Borrow<Fingerprint> for DefPathHash {
     }
 }
 
-/// A [`StableCrateId`] is a 64 bit hash of the crate name combined with all
-/// `-Cmetadata` arguments. It is to [`CrateNum`] what [`DefPathHash`] is to
+/// A [`StableCrateId`] is a 64-bit hash of a crate name, together with all
+/// `-Cmetadata` arguments, and some other data. It is to [`CrateNum`] what [`DefPathHash`] is to
 /// [`DefId`]. It is stable across compilation sessions.
 ///
-/// Since the ID is a hash value there is a (very small) chance that two crates
+/// Since the ID is a hash value, there is a small chance that two crates
 /// end up with the same [`StableCrateId`]. The compiler will check for such
 /// collisions when loading crates and abort compilation in order to avoid
 /// further trouble.
+///
+/// See the discussion in [`DefId`] for more information
+/// on the possibility of hash collisions in rustc,
 #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug)]
 #[derive(HashStable_Generic, Encodable, Decodable)]
 pub struct StableCrateId(pub(crate) u64);
@@ -174,8 +177,14 @@ impl StableCrateId {
         // Also incorporate the rustc version. Otherwise, with -Zsymbol-mangling-version=v0
         // and no -Cmetadata, symbols from the same crate compiled with different versions of
         // rustc are named the same.
-        let rustc_version = option_env!("CFG_VERSION").unwrap_or("unknown version").as_bytes();
-        hasher.write(rustc_version);
+        //
+        // RUSTC_FORCE_INCR_COMP_ARTIFACT_HEADER is used to inject rustc version information
+        // during testing.
+        if let Some(val) = std::env::var_os("RUSTC_FORCE_INCR_COMP_ARTIFACT_HEADER") {
+            hasher.write(val.to_string_lossy().into_owned().as_bytes())
+        } else {
+            hasher.write(option_env!("CFG_VERSION").unwrap_or("unknown version").as_bytes());
+        }
 
         StableCrateId(hasher.finish())
     }
diff --git a/src/test/run-make-fulldeps/crate-hash-rustc-version/Makefile b/src/test/run-make-fulldeps/crate-hash-rustc-version/Makefile
new file mode 100644
index 00000000000..fd66702db7f
--- /dev/null
+++ b/src/test/run-make-fulldeps/crate-hash-rustc-version/Makefile
@@ -0,0 +1,37 @@
+-include ../../run-make-fulldeps/tools.mk
+
+# Ensure that crates compiled with different rustc versions cannot
+# be dynamically linked.
+
+FLAGS := -Cprefer-dynamic -Zsymbol-mangling-version=v0
+UNAME := $(shell uname)
+ifeq ($(UNAME),Linux)
+  EXT=".so"
+  NM_CMD := nm -D
+endif
+ifeq ($(UNAME),Darwin)
+  EXT=".dylib"
+  NM_CMD := nm
+endif
+
+ifndef NM_CMD
+all:
+	exit 0
+else
+all:
+	# a.rs is a dylib
+	$(RUSTC) a.rs --crate-type=dylib $(FLAGS)
+	# Write symbols to disk.
+	$(NM_CMD) $(call DYLIB,a) > $(TMPDIR)/symbolsbefore
+	# b.rs is a binary
+	$(RUSTC) b.rs --extern a=$(TMPDIR)/liba$(EXT) --crate-type=bin -Crpath $(FLAGS)
+	$(call RUN,b)
+	# Now re-compile a.rs with another rustc version
+	RUSTC_FORCE_INCR_COMP_ARTIFACT_HEADER=deadfeed $(RUSTC) a.rs --crate-type=dylib $(FLAGS)
+	# After compiling with a different rustc version, write symbols to disk again.
+	$(NM_CMD) $(call DYLIB,a) > $(TMPDIR)/symbolsafter
+	# As a sanity check, test if the symbols changed:
+	# If the symbols are identical, there's been an error.
+	if diff $(TMPDIR)/symbolsbefore $(TMPDIR)/symbolsafter; then exit 1; fi
+	$(call FAIL,b)
+endif
diff --git a/src/test/run-make-fulldeps/crate-hash-rustc-version/a.rs b/src/test/run-make-fulldeps/crate-hash-rustc-version/a.rs
new file mode 100644
index 00000000000..d65b5ce8e88
--- /dev/null
+++ b/src/test/run-make-fulldeps/crate-hash-rustc-version/a.rs
@@ -0,0 +1,4 @@
+pub fn foo(mut x: String) -> String {
+    x.push_str(", world!");
+    x
+}
diff --git a/src/test/run-make-fulldeps/crate-hash-rustc-version/b.rs b/src/test/run-make-fulldeps/crate-hash-rustc-version/b.rs
new file mode 100644
index 00000000000..316ac26e73f
--- /dev/null
+++ b/src/test/run-make-fulldeps/crate-hash-rustc-version/b.rs
@@ -0,0 +1,8 @@
+extern crate a;
+
+use a::foo;
+
+fn main() {
+    let x = String::from("Hello");
+    println!("{}", foo(x));
+}
diff --git a/src/test/ui/symbol-names/const-generics-demangling.stderr b/src/test/ui/symbol-names/const-generics-demangling.stderr
index 1a8794e6d14..8aa08b8a22c 100644
--- a/src/test/ui/symbol-names/const-generics-demangling.stderr
+++ b/src/test/ui/symbol-names/const-generics-demangling.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RMCsCRATE_HASH_1cINtB0_8UnsignedKhb_E)
+error: symbol-name(_RMCsCRATE_HASH_1cINtB<REF>_8UnsignedKhb_E)
   --> $DIR/const-generics-demangling.rs:8:1
    |
 LL | #[rustc_symbol_name]
@@ -16,7 +16,7 @@ error: demangling-alt(<c::Unsigned<11>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs_CsCRATE_HASH_1cINtB2_6SignedKsn98_E)
+error: symbol-name(_RMs_CsCRATE_HASH_1cINtB<REF>_6SignedKsn98_E)
   --> $DIR/const-generics-demangling.rs:16:1
    |
 LL | #[rustc_symbol_name]
@@ -34,7 +34,7 @@ error: demangling-alt(<c::Signed<-152>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB3_4BoolKb1_E)
+error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB<REF>_4BoolKb1_E)
   --> $DIR/const-generics-demangling.rs:24:1
    |
 LL | #[rustc_symbol_name]
@@ -52,7 +52,7 @@ error: demangling-alt(<c::Bool<true>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB3_4CharKc2202_E)
+error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB<REF>_4CharKc2202_E)
   --> $DIR/const-generics-demangling.rs:32:1
    |
 LL | #[rustc_symbol_name]
diff --git a/src/test/ui/symbol-names/const-generics-str-demangling.stderr b/src/test/ui/symbol-names/const-generics-str-demangling.stderr
index fa69c2a3d72..06d3cdda2f8 100644
--- a/src/test/ui/symbol-names/const-generics-str-demangling.stderr
+++ b/src/test/ui/symbol-names/const-generics-str-demangling.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RMCsCRATE_HASH_1cINtB0_3StrKRe616263_E)
+error: symbol-name(_RMCsCRATE_HASH_1cINtB<REF>_3StrKRe616263_E)
   --> $DIR/const-generics-str-demangling.rs:9:1
    |
 LL | #[rustc_symbol_name]
@@ -16,7 +16,7 @@ error: demangling-alt(<c::Str<"abc">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs_CsCRATE_HASH_1cINtB2_3StrKRe27_E)
+error: symbol-name(_RMs_CsCRATE_HASH_1cINtB<REF>_3StrKRe27_E)
   --> $DIR/const-generics-str-demangling.rs:15:1
    |
 LL | #[rustc_symbol_name]
@@ -34,7 +34,7 @@ error: demangling-alt(<c::Str<"'">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB3_3StrKRe090a_E)
+error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB<REF>_3StrKRe090a_E)
   --> $DIR/const-generics-str-demangling.rs:21:1
    |
 LL | #[rustc_symbol_name]
@@ -52,7 +52,7 @@ error: demangling-alt(<c::Str<"\t\n">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB3_3StrKRee28882c3bc_E)
+error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB<REF>_3StrKRee28882c3bc_E)
   --> $DIR/const-generics-str-demangling.rs:27:1
    |
 LL | #[rustc_symbol_name]
@@ -70,7 +70,7 @@ error: demangling-alt(<c::Str<"∂ü">>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs2_CsCRATE_HASH_1cINtB3_3StrKRee183a1e18390e183ade1839be18394e1839ae18390e183935fe18392e18394e1839be183a0e18398e18394e1839ae183985fe183a1e18390e18393e18398e1839ae18398_E)
+error: symbol-name(_RMs2_CsCRATE_HASH_1cINtB<REF>_3StrKRee183a1e18390e183ade1839be18394e1839ae18390e183935fe18392e18394e1839be183a0e18398e18394e1839ae183985fe183a1e18390e18393e18398e1839ae18398_E)
   --> $DIR/const-generics-str-demangling.rs:33:1
    |
 LL | #[rustc_symbol_name]
@@ -88,7 +88,7 @@ error: demangling-alt(<c::Str<"საჭმელად_გემრიელი
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs3_CsCRATE_HASH_1cINtB3_3StrKRef09f908af09fa688f09fa686f09f90ae20c2a720f09f90b6f09f9192e29895f09f94a520c2a720f09fa7a1f09f929bf09f929af09f9299f09f929c_E)
+error: symbol-name(_RMs3_CsCRATE_HASH_1cINtB<REF>_3StrKRef09f908af09fa688f09fa686f09f90ae20c2a720f09f90b6f09f9192e29895f09f94a520c2a720f09fa7a1f09f929bf09f929af09f9299f09f929c_E)
   --> $DIR/const-generics-str-demangling.rs:39:1
    |
 LL | #[rustc_symbol_name]
diff --git a/src/test/ui/symbol-names/const-generics-structural-demangling.stderr b/src/test/ui/symbol-names/const-generics-structural-demangling.stderr
index f38342427b1..a4c997477ee 100644
--- a/src/test/ui/symbol-names/const-generics-structural-demangling.stderr
+++ b/src/test/ui/symbol-names/const-generics-structural-demangling.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RMCsCRATE_HASH_1cINtB0_7RefByteKRh7b_E)
+error: symbol-name(_RMCsCRATE_HASH_1cINtB<REF>_7RefByteKRh7b_E)
   --> $DIR/const-generics-structural-demangling.rs:14:1
    |
 LL | #[rustc_symbol_name]
@@ -16,7 +16,7 @@ error: demangling-alt(<c::RefByte<{&123}>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs_CsCRATE_HASH_1cINtB2_6RefZstKRAEE)
+error: symbol-name(_RMs_CsCRATE_HASH_1cINtB<REF>_6RefZstKRAEE)
   --> $DIR/const-generics-structural-demangling.rs:24:1
    |
 LL | #[rustc_symbol_name]
@@ -34,7 +34,7 @@ error: demangling-alt(<c::RefZst<{&[]}>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB3_11Array3BytesKAh1_h2_h3_EE)
+error: symbol-name(_RMs0_CsCRATE_HASH_1cINtB<REF>_11Array3BytesKAh1_h2_h3_EE)
   --> $DIR/const-generics-structural-demangling.rs:32:1
    |
 LL | #[rustc_symbol_name]
@@ -52,7 +52,7 @@ error: demangling-alt(<c::Array3Bytes<{[1, 2, 3]}>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB3_13TupleByteBoolKTh1_b0_EE)
+error: symbol-name(_RMs1_CsCRATE_HASH_1cINtB<REF>_13TupleByteBoolKTh1_b0_EE)
   --> $DIR/const-generics-structural-demangling.rs:40:1
    |
 LL | #[rustc_symbol_name]
@@ -70,7 +70,7 @@ error: demangling-alt(<c::TupleByteBool<{(1, false)}>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs2_CsCRATE_HASH_1cINtB3_11OptionUsizeKVNtINtNtCsCRATE_HASH_4core6option6OptionjE4NoneUE)
+error: symbol-name(_RMs2_CsCRATE_HASH_1cINtB<REF>_11OptionUsizeKVNtINtNtCsCRATE_HASH_4core6option6OptionjE4NoneUE)
   --> $DIR/const-generics-structural-demangling.rs:50:1
    |
 LL | #[rustc_symbol_name]
@@ -88,7 +88,7 @@ error: demangling-alt(<c::OptionUsize<{core::option::Option::<usize>::None}>>)
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs3_CsCRATE_HASH_1cINtB3_11OptionUsizeKVNtINtNtCsCRATE_HASH_4core6option6OptionjE4SomeTj0_EE)
+error: symbol-name(_RMs3_CsCRATE_HASH_1cINtB<REF>_11OptionUsizeKVNtINtNtCsCRATE_HASH_4core6option6OptionjE4SomeTj0_EE)
   --> $DIR/const-generics-structural-demangling.rs:58:1
    |
 LL | #[rustc_symbol_name]
@@ -106,7 +106,7 @@ error: demangling-alt(<c::OptionUsize<{core::option::Option::<usize>::Some(0)}>>
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs4_CsCRATE_HASH_1cINtB3_4Foo_KVNtB3_3FooS1sRe616263_2chc78_5sliceRAh1_h2_h3_EEE)
+error: symbol-name(_RMs4_CsCRATE_HASH_1cINtB<REF>_4Foo_KVNtB<REF>_3FooS1sRe616263_2chc78_5sliceRAh1_h2_h3_EEE)
   --> $DIR/const-generics-structural-demangling.rs:72:1
    |
 LL | #[rustc_symbol_name]
@@ -124,7 +124,7 @@ error: demangling-alt(<c::Foo_<{c::Foo { s: "abc", ch: 'x', slice: &[1, 2, 3] }}
 LL | #[rustc_symbol_name]
    | ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RMs9_CsCRATE_HASH_1cINtB3_4Bar_KVNtB3_3BarS1xh7b_s_1xt1000_EE)
+error: symbol-name(_RMs9_CsCRATE_HASH_1cINtB<REF>_4Bar_KVNtB<REF>_3BarS1xh7b_s_1xt1000_EE)
   --> $DIR/const-generics-structural-demangling.rs:88:5
    |
 LL |     #[rustc_symbol_name]
diff --git a/src/test/ui/symbol-names/impl1.v0.stderr b/src/test/ui/symbol-names/impl1.v0.stderr
index c9a448f8265..06778e57fb1 100644
--- a/src/test/ui/symbol-names/impl1.v0.stderr
+++ b/src/test/ui/symbol-names/impl1.v0.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RNvMNtCsCRATE_HASH_5impl13fooNtB2_3Foo3bar)
+error: symbol-name(_RNvMNtCsCRATE_HASH_5impl13fooNtB<REF>_3Foo3bar)
   --> $DIR/impl1.rs:14:9
    |
 LL |         #[rustc_symbol_name]
@@ -22,7 +22,7 @@ error: def-path(foo::Foo::bar)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RNvMNtCsCRATE_HASH_5impl13barNtNtB4_3foo3Foo3baz)
+error: symbol-name(_RNvMNtCsCRATE_HASH_5impl13barNtNtB<REF>_3foo3Foo3baz)
   --> $DIR/impl1.rs:32:9
    |
 LL |         #[rustc_symbol_name]
@@ -46,7 +46,7 @@ error: def-path(bar::<impl foo::Foo>::baz)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RNvXNCNvCsCRATE_HASH_5impl14mains_0ARDNtB6_3Foop5AssocFG_KCRL0_hvEuNtB6_9AutoTraitEL_j3_NtB2_3Bar6method)
+error: symbol-name(_RNvXNCNvCsCRATE_HASH_5impl14mains_0ARDNtB<REF>_3Foop5AssocFG_KCRL0_hvEuNtB<REF>_9AutoTraitEL_j3_NtB<REF>_3Bar6method)
   --> $DIR/impl1.rs:62:13
    |
 LL |             #[rustc_symbol_name]
diff --git a/src/test/ui/symbol-names/issue-60925.v0.stderr b/src/test/ui/symbol-names/issue-60925.v0.stderr
index dd95612d8c8..1cddba92085 100644
--- a/src/test/ui/symbol-names/issue-60925.v0.stderr
+++ b/src/test/ui/symbol-names/issue-60925.v0.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RNvMNtCsCRATE_HASH_11issue_609253fooINtB2_3FooNtNtB4_4llvm3FooE3foo)
+error: symbol-name(_RNvMNtCsCRATE_HASH_11issue_609253fooINtB<REF>_3FooNtNtB<REF>_4llvm3FooE3foo)
   --> $DIR/issue-60925.rs:21:9
    |
 LL |         #[rustc_symbol_name]
diff --git a/src/test/ui/symbol-names/issue-75326.v0.stderr b/src/test/ui/symbol-names/issue-75326.v0.stderr
index c691b11a28f..446fb8d6cf6 100644
--- a/src/test/ui/symbol-names/issue-75326.v0.stderr
+++ b/src/test/ui/symbol-names/issue-75326.v0.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RNvXINICsCRATE_HASH_11issue_75326s_0pppEINtB5_3FooppENtB5_9Iterator24nextB5_)
+error: symbol-name(_RNvXINICsCRATE_HASH_11issue_75326s_0pppEINtB<REF>_3FooppENtB<REF>_9Iterator24nextB<REF>_)
   --> $DIR/issue-75326.rs:41:5
    |
 LL |     #[rustc_symbol_name]
diff --git a/src/test/ui/symbol-names/trait-objects.v0.stderr b/src/test/ui/symbol-names/trait-objects.v0.stderr
index 8d55f42a419..6c5e55ed2ae 100644
--- a/src/test/ui/symbol-names/trait-objects.v0.stderr
+++ b/src/test/ui/symbol-names/trait-objects.v0.stderr
@@ -1,4 +1,4 @@
-error: symbol-name(_RNvXCsCRATE_HASH_13trait_objectsRDG_INtNtNtCsCRATE_HASH_4core3ops8function5FnMutTRL0_hEEp6OutputuEL_NtB2_3Bar6method)
+error: symbol-name(_RNvXCsCRATE_HASH_13trait_objectsRDG_INtNtNtCsCRATE_HASH_4core3ops8function5FnMutTRL0_hEEp6OutputuEL_NtB<REF>_3Bar6method)
   --> $DIR/trait-objects.rs:15:5
    |
 LL |     #[rustc_symbol_name]
@@ -16,7 +16,7 @@ error: demangling-alt(<&dyn for<'a> core::ops::function::FnMut<(&'a u8,), Output
 LL |     #[rustc_symbol_name]
    |     ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RNvXs_CsCRATE_HASH_13trait_objectsRDG_INtNtNtCsCRATE_HASH_4core3ops8function5FnMutTRL0_hEEp6OutputuNtNtBI_6marker4SendEL_NtB4_3Foo6method)
+error: symbol-name(_RNvXs_CsCRATE_HASH_13trait_objectsRDG_INtNtNtCsCRATE_HASH_4core3ops8function5FnMutTRL0_hEEp6OutputuNtNtB<REF>_6marker4SendEL_NtB<REF>_3Foo6method)
   --> $DIR/trait-objects.rs:27:5
    |
 LL |     #[rustc_symbol_name]
@@ -34,7 +34,7 @@ error: demangling-alt(<&dyn for<'a> core::ops::function::FnMut<(&'a u8,), Output
 LL |     #[rustc_symbol_name]
    |     ^^^^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_RNvXs0_CsCRATE_HASH_13trait_objectsRDG_INtNtNtCsCRATE_HASH_4core3ops8function5FnMutTRL0_hEEp6OutputuNtNtBJ_6marker4SendEL_NtB5_3Baz6method)
+error: symbol-name(_RNvXs0_CsCRATE_HASH_13trait_objectsRDG_INtNtNtCsCRATE_HASH_4core3ops8function5FnMutTRL0_hEEp6OutputuNtNtB<REF>_6marker4SendEL_NtB<REF>_3Baz6method)
   --> $DIR/trait-objects.rs:39:5
    |
 LL |     #[rustc_symbol_name]
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index ae97df583a3..f039ba59d23 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -3513,6 +3513,9 @@ impl<'test> TestCx<'test> {
         const V0_CRATE_HASH_PREFIX_REGEX: &str = r"_R.*?Cs[0-9a-zA-Z]+_";
         const V0_CRATE_HASH_REGEX: &str = r"Cs[0-9a-zA-Z]+_";
         const V0_CRATE_HASH_PLACEHOLDER: &str = r"CsCRATE_HASH_";
+        const V0_BACK_REF_PREFIX_REGEX: &str = r"\(_R.*?B[0-9a-zA-Z]_";
+        const V0_BACK_REF_REGEX: &str = r"B[0-9a-zA-Z]_";
+        const V0_BACK_REF_PLACEHOLDER: &str = r"B<REF>_";
         const LEGACY_SYMBOL_HASH_REGEX: &str = r"h[\w]{16}E?\)";
         const LEGACY_SYMBOL_HASH_PLACEHOLDER: &str = r"h<SYMBOL_HASH>)";
         let test_name = self
@@ -3547,6 +3550,16 @@ impl<'test> TestCx<'test> {
                 .replace_all(&normalized, V0_CRATE_HASH_PLACEHOLDER)
                 .into_owned();
         }
+        let back_ref_prefix_re = Regex::new(V0_BACK_REF_PREFIX_REGEX).unwrap();
+        if back_ref_prefix_re.is_match(&normalized) {
+            // Normalize back references (see RFC 2603)
+            let back_ref_regex = format!("{}", V0_BACK_REF_REGEX);
+            let back_ref_placeholder = format!("{}", V0_BACK_REF_PLACEHOLDER);
+            normalized = Regex::new(&back_ref_regex)
+                .unwrap()
+                .replace_all(&normalized, back_ref_placeholder)
+                .into_owned();
+        }
         // Normalize legacy mangled symbols
         normalized = Regex::new(LEGACY_SYMBOL_HASH_REGEX)
             .unwrap()