[clang] [clang-format] Fix crashes when the macro expansion is empty (PR #119428)

[via cfe-commits]

https://github.com/amane-ame updated https://github.com/llvm/llvm-project/pull/119428

>From 3a4c1a924faef3a7a09126694fcb943bd7083451 Mon Sep 17 00:00:00 2001
From: amane-ame <i at amane-a.me>
Date: Wed, 11 Dec 2024 02:13:43 +0800
Subject: [PATCH 1/4] Fix crashes when the macro expansion is empty

---
 clang/lib/Format/MacroExpander.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/clang/lib/Format/MacroExpander.cpp b/clang/lib/Format/MacroExpander.cpp
index fd2a16894d643d..ed9e51dfbfef1f 100644
--- a/clang/lib/Format/MacroExpander.cpp
+++ b/clang/lib/Format/MacroExpander.cpp
@@ -233,6 +233,10 @@ MacroExpander::expand(FormatToken *ID,
   if (Result.size() > 1) {
     ++Result[0]->MacroCtx->StartOfExpansion;
     ++Result[Result.size() - 2]->MacroCtx->EndOfExpansion;
+  } else {
+    // If the macro expansion is empty, mark the start and end
+    Result[0]->MacroCtx->StartOfExpansion = 1;
+    Result[0]->MacroCtx->EndOfExpansion = 1;
   }
   return Result;
 }

>From 8bf68f87b897bab9da9464d594082be5012afdb1 Mon Sep 17 00:00:00 2001
From: amane-ame <i at amane-a.me>
Date: Sun, 15 Dec 2024 15:15:17 +0800
Subject: [PATCH 2/4] [clang-format] Add a testcase for empty macro

---
 clang/test/Format/empty-macro.cpp | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 clang/test/Format/empty-macro.cpp

diff --git a/clang/test/Format/empty-macro.cpp b/clang/test/Format/empty-macro.cpp
new file mode 100644
index 00000000000000..81b255219b0c2b
--- /dev/null
+++ b/clang/test/Format/empty-macro.cpp
@@ -0,0 +1,5 @@
+// RUN: grep -Ev "// *[A-Z-]+:" %s | clang-format -style="{Macros: [A(x)=x]}" \
+// RUN:   | FileCheck -strict-whitespace %s
+
+// CHECK: A()
+A()

>From 37a5b1b1877a7292869a93f7bfd4c09999ec9814 Mon Sep 17 00:00:00 2001
From: amane-ame <i at amane-a.me>
Date: Mon, 16 Dec 2024 16:30:27 +0800
Subject: [PATCH 3/4] [clang-format] Move the testcase to unittest

---
 clang/test/Format/empty-macro.cpp                   |  5 -----
 .../unittests/Format/MacroCallReconstructorTest.cpp | 13 +++++++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)
 delete mode 100644 clang/test/Format/empty-macro.cpp

diff --git a/clang/test/Format/empty-macro.cpp b/clang/test/Format/empty-macro.cpp
deleted file mode 100644
index 81b255219b0c2b..00000000000000
--- a/clang/test/Format/empty-macro.cpp
+++ /dev/null
@@ -1,5 +0,0 @@
-// RUN: grep -Ev "// *[A-Z-]+:" %s | clang-format -style="{Macros: [A(x)=x]}" \
-// RUN:   | FileCheck -strict-whitespace %s
-
-// CHECK: A()
-A()
diff --git a/clang/unittests/Format/MacroCallReconstructorTest.cpp b/clang/unittests/Format/MacroCallReconstructorTest.cpp
index b4ee8d0e37efa8..08088fe48fdf6a 100644
--- a/clang/unittests/Format/MacroCallReconstructorTest.cpp
+++ b/clang/unittests/Format/MacroCallReconstructorTest.cpp
@@ -217,6 +217,19 @@ TEST_F(MacroCallReconstructorTest, Identifier) {
   EXPECT_THAT(std::move(Unexp).takeResult(), matchesLine(line(U.consume("X"))));
 }
 
+TEST_F(MacroCallReconstructorTest, EmptyExpansion) {
+  auto Macros = createExpander({"A(x)=y"});
+  Expansion Exp(Lex, *Macros);
+  TokenList Call = Exp.expand("A", {""});
+
+  MacroCallReconstructor Unexp(0, Exp.getUnexpanded());
+  Unexp.addLine(line(Exp.getTokens()));
+  EXPECT_TRUE(Unexp.finished());
+  Matcher U(Call, Lex);
+  EXPECT_THAT(std::move(Unexp).takeResult(),
+              matchesLine(line(U.consume("A()"))));
+}
+
 TEST_F(MacroCallReconstructorTest, NestedLineWithinCall) {
   auto Macros = createExpander({"C(a)=class X { a; };"});
   Expansion Exp(Lex, *Macros);

>From e46f0e059d61fb370c5f76ede99423846f5959c8 Mon Sep 17 00:00:00 2001
From: amane-ame <i at amane-a.me>
Date: Thu, 19 Dec 2024 17:11:16 +0800
Subject: [PATCH 4/4] [clang-format] Fix about Tokens in
 MacroCallReconstructorTest

When the macro expansion is empty, the tok::eof Token should be preserved.
The reason is we have marked the start point and end point on this token in MacroExpander::expand.
---
 clang/unittests/Format/MacroCallReconstructorTest.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/clang/unittests/Format/MacroCallReconstructorTest.cpp b/clang/unittests/Format/MacroCallReconstructorTest.cpp
index 08088fe48fdf6a..1364de0727f4e7 100644
--- a/clang/unittests/Format/MacroCallReconstructorTest.cpp
+++ b/clang/unittests/Format/MacroCallReconstructorTest.cpp
@@ -65,7 +65,9 @@ class Expansion {
     }
     Unexpanded[ID] = std::move(UnexpandedLine);
 
-    auto Expanded = uneof(Macros.expand(ID, Args));
+    auto Expanded = Macros.expand(ID, Args);
+    if (Expanded.size() > 1)
+      Expanded = uneof(Expanded);
     Tokens.append(Expanded.begin(), Expanded.end());
 
     TokenList UnexpandedTokens;
@@ -218,7 +220,7 @@ TEST_F(MacroCallReconstructorTest, Identifier) {
 }
 
 TEST_F(MacroCallReconstructorTest, EmptyExpansion) {
-  auto Macros = createExpander({"A(x)=y"});
+  auto Macros = createExpander({"A(x)=x"});
   Expansion Exp(Lex, *Macros);
   TokenList Call = Exp.expand("A", {""});