[clang] [clang-format] Handle sizeof in C compound literals (PR #187633)

[via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/187633

Fixes #168237

>From ba0c47f2f679423b641b14859b4b68e34ebbfc68 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Thu, 19 Mar 2026 22:46:50 -0700
Subject: [PATCH] [clang-format] Handle sizeof in C compound literals

Fixes #168237
---
 clang/lib/Format/TokenAnnotator.cpp   | 11 +++++++++++
 clang/unittests/Format/FormatTest.cpp |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 55a6d1a9427f9..ee14469cfc968 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -4991,6 +4991,17 @@ bool TokenAnnotator::spaceRequiredBetween(const AnnotatedLine &Line,
                spaceRequiredBeforeParens(Right);
       }
     }
+    auto CompoundLiteral = [](const FormatToken &Tok) {
+      if (Tok.isNot(tok::l_paren))
+        return false;
+      const auto *RParen = Tok.MatchingParen;
+      if (!RParen)
+        return false;
+      const auto *Next = RParen->Next;
+      return Next && Next->is(tok::l_brace) && Next->is(BK_BracedInit);
+    };
+    if (Left.is(tok::kw_sizeof) && CompoundLiteral(Right))
+      return true;
     // Handle builtins like identifiers.
     if (Line.Type != LT_PreprocessorDirective &&
         (Left.Tok.getIdentifierInfo() || Left.is(tok::r_paren))) {
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 7628195e74a77..f88f930bfd23f 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -17532,6 +17532,8 @@ TEST_F(FormatTest, ConfigurableSpaceBeforeParens) {
                "#elif ((a || b) && c) || d\n"
                "#endif",
                NoSpace);
+  // Space between sizeof and C compound literal.
+  verifyFormat("a = sizeof (int){};", NoSpace);
 
   FormatStyle Space = getLLVMStyle();
   Space.SpaceBeforeParens = FormatStyle::SBPO_Always;