[clang] [clang-format] Fix crash involving array designators and dangling comma (PR #77045)

[via cfe-commits]

https://github.com/XDeme created https://github.com/llvm/llvm-project/pull/77045

Fixes llvm/llvm-project#76716
Added a check to prevent null deferencing

>From d9cbbe48b96d27bff3fc926b60d039ed05f00489 Mon Sep 17 00:00:00 2001
From: XDeme <fernando.tagawa.gamail.com at gmail.com>
Date: Fri, 5 Jan 2024 01:23:16 -0300
Subject: [PATCH] [clang-format] Fix crash involving array designators and
 dangling comma Fixes llvm/llvm-project#76716 Added a check to prevent null
 deferencing

---
 clang/lib/Format/WhitespaceManager.cpp | 3 ++-
 clang/unittests/Format/FormatTest.cpp  | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
index 3bc6915b8df0a7..95693f4588c631 100644
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -1444,7 +1444,8 @@ WhitespaceManager::CellDescriptions WhitespaceManager::getCells(unsigned Start,
       } else if (C.Tok->is(tok::comma)) {
         if (!Cells.empty())
           Cells.back().EndIndex = i;
-        if (C.Tok->getNextNonComment()->isNot(tok::r_brace)) // dangling comma
+        const FormatToken *Next = C.Tok->getNextNonComment();
+        if (Next && Next->isNot(tok::r_brace)) // dangling comma
           ++Cell;
       }
     } else if (Depth == 1) {
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 881993ede17c3d..c9f91953c13f52 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -21084,6 +21084,12 @@ TEST_F(FormatTest, CatchAlignArrayOfStructuresLeftAlignment) {
       "};",
       Style);
 
+  verifyNoCrash("Foo f[] = {\n"
+                "    [0] = { 1, },\n"
+                "    [1] { 1, },\n"
+                "};",
+                Style);
+
   verifyFormat("return GradForUnaryCwise(g, {\n"
                "                                {{\"sign\"}, \"Sign\", {\"x\", "
                "\"dy\"}   },\n"