[clang-tools-extra] [clang-tidy] fix crash in altera-id-dependent-backward-branch (PR #113833)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tidy

Author: Julian Schmidt (5chmidti)

<details>
<summary>Changes</summary>

Add some checks for `nullptr` and change some `dyn_cast` to
`dyn_cast_if_present` to avoid crashes.

Fixes #<!-- -->55408


---
Full diff: https://github.com/llvm/llvm-project/pull/113833.diff


1 Files Affected:

- (modified) clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp (+15-4) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp b/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp
index 09f7d8c5c2f952..94db0a793cf53d 100644
--- a/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp
@@ -78,16 +78,22 @@ void IdDependentBackwardBranchCheck::registerMatchers(MatchFinder *Finder) {
 
 IdDependentBackwardBranchCheck::IdDependencyRecord *
 IdDependentBackwardBranchCheck::hasIdDepVar(const Expr *Expression) {
+  if (!Expression)
+    return nullptr;
+
   if (const auto *Declaration = dyn_cast<DeclRefExpr>(Expression)) {
     // It is a DeclRefExpr, so check if it's an ID-dependent variable.
-    const auto *CheckVariable = dyn_cast<VarDecl>(Declaration->getDecl());
+    const auto *CheckVariable =
+        dyn_cast_if_present<VarDecl>(Declaration->getDecl());
+    if (!CheckVariable)
+      return nullptr;
     auto FoundVariable = IdDepVarsMap.find(CheckVariable);
     if (FoundVariable == IdDepVarsMap.end())
       return nullptr;
     return &(FoundVariable->second);
   }
   for (const auto *Child : Expression->children())
-    if (const auto *ChildExpression = dyn_cast<Expr>(Child))
+    if (const auto *ChildExpression = dyn_cast_if_present<Expr>(Child))
       if (IdDependencyRecord *Result = hasIdDepVar(ChildExpression))
         return Result;
   return nullptr;
@@ -95,16 +101,21 @@ IdDependentBackwardBranchCheck::hasIdDepVar(const Expr *Expression) {
 
 IdDependentBackwardBranchCheck::IdDependencyRecord *
 IdDependentBackwardBranchCheck::hasIdDepField(const Expr *Expression) {
+  if (!Expression)
+    return nullptr;
+
   if (const auto *MemberExpression = dyn_cast<MemberExpr>(Expression)) {
     const auto *CheckField =
-        dyn_cast<FieldDecl>(MemberExpression->getMemberDecl());
+        dyn_cast_if_present<FieldDecl>(MemberExpression->getMemberDecl());
+    if (!CheckField)
+      return nullptr;
     auto FoundField = IdDepFieldsMap.find(CheckField);
     if (FoundField == IdDepFieldsMap.end())
       return nullptr;
     return &(FoundField->second);
   }
   for (const auto *Child : Expression->children())
-    if (const auto *ChildExpression = dyn_cast<Expr>(Child))
+    if (const auto *ChildExpression = dyn_cast_if_present<Expr>(Child))
       if (IdDependencyRecord *Result = hasIdDepField(ChildExpression))
         return Result;
   return nullptr;

``````````

</details>


https://github.com/llvm/llvm-project/pull/113833