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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (vabridgers)

<details>
<summary>Changes</summary>

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: &lt;root&gt;/clang/lib/StaticAnalyzer/Core/CheckerManager.cpp:56:
   void clang::ento::CheckerManager::finishedCheckerRegistration():
     Assertion `Event.second.HasDispatcher &amp;&amp; "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 &lt;addr&gt; 
clang::ento::CheckerManager::finishedCheckerRegistration()
 #<!-- -->8 &lt;addr&gt; 
clang::ento::CheckerManager::CheckerManager(clang::ASTContext&amp;,
             clang::AnalyzerOptions&amp;, clang::Preprocessor const&amp;,
             llvm::ArrayRef&lt;std::__cxx11::basic_string&lt;char, 
std::char_traits&lt;char&gt;,
             std::allocator&lt;char&gt;&gt;&gt;, 
llvm::ArrayRef&lt;std::function&lt;void 
(clang::ento::CheckerRegistry&amp;)&gt;&gt;)

---
Full diff: https://github.com/llvm/llvm-project/pull/107294.diff


2 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp (+1) 
- (added) clang/test/Analysis/nullability-nocrash.c (+4) 


``````````diff
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

``````````

</details>


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