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

[via cfe-commits]

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

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&)>>)

>From 7e373835f1d6739e388a2c84d2f52a606df4fc45 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..d75dcb5a8cd644 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