[clang] [analyzer] Prevent crash due to missing EventDispatch in corner case (PR #107294)

[via cfe-commits]

https://github.com/vabridgers updated https://github.com/llvm/llvm-project/pull/107294

>From e8b71519145c710d01734ce01bd6360979a1e577 Mon Sep 17 00:00:00 2001
From: Vince Bridgers <vince.a.bridgers at ericsson.com>
Date: Wed, 4 Sep 2024 20:36:06 +0200
Subject: [PATCH] [analyzer] Prevent crash due to missing EventDispatch in
 corner case

Random testing revealed it's possible to crash the analyzer through a rare
command line invocation:

clang -cc1 -analyze -analyzer-checker=nullability empty.c

where the source file, empty.c is an empty source file. This change simply
registers the ImplictNullDeref Event Dispatcher as is done in other similar
checks to avoid the crash.

clang: <root>/clang/lib/StaticAnalyzer/Core/CheckerManager.cpp:56:
   void clang::ento::CheckerManager::finishedCheckerRegistration():
     Assertion `Event.second.HasDispatcher && "No dispatcher registered for an event"' failed.

PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/

Stack dump:
0.      Program arguments: clang -cc1 -analyze -analyzer-checker=nullability nullability-nocrash.c
 #0 ...
 ...
 #7 <addr> clang::ento::CheckerManager::finishedCheckerRegistration()
 #8 <addr> clang::ento::CheckerManager::CheckerManager(clang::ASTContext&,
             clang::AnalyzerOptions&, clang::Preprocessor const&,
             llvm::ArrayRef<std::__cxx11::basic_string<char, std::char_traits<char>,
             std::allocator<char>>>, llvm::ArrayRef<std::function<void (clang::ento::CheckerRegistry&)>>)
---
 clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp | 1 +
 clang/test/Analysis/nullability-nocrash.c                | 4 ++++
 2 files changed, 5 insertions(+)
 create mode 100644 clang/test/Analysis/nullability-nocrash.c

diff --git a/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
index 04472bb3895a78..65667ba746d826 100644
--- a/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
@@ -84,6 +84,7 @@ class NullabilityChecker
                      check::PostCall, check::PostStmt<ExplicitCastExpr>,
                      check::PostObjCMessage, check::DeadSymbols, eval::Assume,
                      check::Location, check::Event<ImplicitNullDerefEvent>,
+                     EventDispatcher<ImplicitNullDerefEvent>,
                      check::BeginFunction> {
 
 public:
diff --git a/clang/test/Analysis/nullability-nocrash.c b/clang/test/Analysis/nullability-nocrash.c
new file mode 100644
index 00000000000000..4102a4fd3a846f
--- /dev/null
+++ b/clang/test/Analysis/nullability-nocrash.c
@@ -0,0 +1,4 @@
+// RUN: %clang_analyze_cc1 -w -analyzer-checker=nullability \
+// RUN:                       -analyzer-output=text -verify %s
+//
+// expected-no-diagnostics