From fe43a4cb564ef6dc731d52e8246c7ecbd1fd6bf5 Mon Sep 17 00:00:00 2001
From: Chris Mihelich <cmihelic@google.com>
Date: Wed, 5 Jun 2024 15:18:52 -0700
Subject: Demangle preincrement and predecrement, pp_... and mm_....

PiperOrigin-RevId: 640666300
Change-Id: I1dae13f515de5fae3768a54c3808b80083ed63f8
---
 absl/debugging/internal/demangle.cc      | 11 ++++++
 absl/debugging/internal/demangle_test.cc | 60 ++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 8887ee47..7fe8439b 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -1984,6 +1984,8 @@ static bool ParseBracedExpression(State *state) {
 // <expression> ::= <1-ary operator-name> <expression>
 //              ::= <2-ary operator-name> <expression> <expression>
 //              ::= <3-ary operator-name> <expression> <expression> <expression>
+//              ::= pp_ <expression>  # ++e; pp <expression> is e++
+//              ::= mm_ <expression>  # --e; mm <expression> is e--
 //              ::= cl <expression>+ E
 //              ::= cp <simple-id> <expression>* E # Clang-specific.
 //              ::= so <type> <expression> [<number>] <union-selector>* [p] E
@@ -2037,6 +2039,15 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // Preincrement and predecrement.  Postincrement and postdecrement are handled
+  // by the operator-name logic later on.
+  if ((ParseThreeCharToken(state, "pp_") ||
+       ParseThreeCharToken(state, "mm_")) &&
+      ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   // Clang-specific "cp <simple-id> <expression>* E"
   //   https://clang.llvm.org/doxygen/ItaniumMangle_8cpp_source.html#l04338
   if (ParseTwoCharToken(state, "cp") && ParseSimpleId(state) &&
diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index 85a20f0a..7d455651 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -768,6 +768,66 @@ TEST(Demangle, SubobjectAddresses) {
   EXPECT_STREQ("f<>()", tmp);
 }
 
+TEST(Demangle, Preincrement) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> auto f(T t) -> decltype(T{++t}) { return t; }
+  // template auto f<int>(int t) -> decltype(int{++t});
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // decltype(int{++fp}) f<int>(int)
+  EXPECT_TRUE(Demangle("_Z1fIiEDTtlT_pp_fp_EES0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
+TEST(Demangle, Postincrement) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> auto f(T t) -> decltype(T{t++}) { return t; }
+  // template auto f<int>(int t) -> decltype(int{t++});
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // decltype(int{fp++}) f<int>(int)
+  EXPECT_TRUE(Demangle("_Z1fIiEDTtlT_ppfp_EES0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
+TEST(Demangle, Predecrement) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> auto f(T t) -> decltype(T{--t}) { return t; }
+  // template auto f<int>(int t) -> decltype(int{--t});
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // decltype(int{--fp}) f<int>(int)
+  EXPECT_TRUE(Demangle("_Z1fIiEDTtlT_mm_fp_EES0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
+TEST(Demangle, Postdecrement) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> auto f(T t) -> decltype(T{t--}) { return t; }
+  // template auto f<int>(int t) -> decltype(int{t--});
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // decltype(int{fp--}) f<int>(int)
+  EXPECT_TRUE(Demangle("_Z1fIiEDTtlT_mmfp_EES0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 TEST(Demangle, UnaryFoldExpressions) {
   char tmp[80];
 
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