From 44e077d6660f06e5500a604b48f8c109396d6d0d Mon Sep 17 00:00:00 2001
From: Chris Mihelich <cmihelic@google.com>
Date: Tue, 28 May 2024 15:15:46 -0700
Subject: Demangle thread_local helper functions.

PiperOrigin-RevId: 638039514
Change-Id: I623d87e91ebe0a1166fee175151179b61ef54249
---
 absl/debugging/internal/demangle.cc      | 27 +++++++++++++++++++++++----
 absl/debugging/internal/demangle_test.cc | 10 ++++++++++
 2 files changed, 33 insertions(+), 4 deletions(-)

(limited to 'absl')

diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 1290ff65..36713e77 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -1049,7 +1049,8 @@ static bool ParseOperatorName(State *state, int *arity) {
 //                ::= TT <type>
 //                ::= TI <type>
 //                ::= TS <type>
-//                ::= TH <type>  # thread-local
+//                ::= TW <name>  # thread-local wrapper
+//                ::= TH <name>  # thread-local initialization
 //                ::= Tc <call-offset> <call-offset> <(base) encoding>
 //                ::= GV <(object) name>
 //                ::= T <call-offset> <(base) encoding>
@@ -1062,13 +1063,31 @@ static bool ParseOperatorName(State *state, int *arity) {
 //                ::= Th <call-offset> <(base) encoding>
 //                ::= Tv <call-offset> <(base) encoding>
 //
-// Note: we don't care much about them since they don't appear in
-// stack traces.  The are special data.
+// Note: Most of these are special data, not functions that occur in stack
+// traces.  Exceptions are TW and TH, which denote functions supporting the
+// thread_local feature.  For these see:
+//
+// https://maskray.me/blog/2021-02-14-all-about-thread-local-storage
 static bool ParseSpecialName(State *state) {
   ComplexityGuard guard(state);
   if (guard.IsTooComplex()) return false;
   ParseState copy = state->parse_state;
-  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "VTISH") &&
+
+  if (ParseTwoCharToken(state, "TW")) {
+    MaybeAppend(state, "thread-local wrapper routine for ");
+    if (ParseName(state)) return true;
+    state->parse_state = copy;
+    return false;
+  }
+
+  if (ParseTwoCharToken(state, "TH")) {
+    MaybeAppend(state, "thread-local initialization routine for ");
+    if (ParseName(state)) return true;
+    state->parse_state = copy;
+    return false;
+  }
+
+  if (ParseOneCharToken(state, 'T') && ParseCharClass(state, "VTIS") &&
       ParseType(state)) {
     return true;
   }
diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index 5fd50aff..a2586e34 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -631,6 +631,16 @@ TEST(Demangle, ReferenceQualifiedFunctionTypes) {
   EXPECT_STREQ("f()", tmp);
 }
 
+TEST(Demangle, ThreadLocalWrappers) {
+  char tmp[80];
+
+  EXPECT_TRUE(Demangle("_ZTWN2ns3varE", tmp, sizeof(tmp)));
+  EXPECT_STREQ("thread-local wrapper routine for ns::var", tmp);
+
+  EXPECT_TRUE(Demangle("_ZTHN2ns3varE", tmp, sizeof(tmp)));
+  EXPECT_STREQ("thread-local initialization routine for ns::var", tmp);
+}
+
 // Test one Rust symbol to exercise Demangle's delegation path.  Rust demangling
 // itself is more thoroughly tested in demangle_rust_test.cc.
 TEST(Demangle, DelegatesToDemangleRustSymbolEncoding) {
-- 
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