[clang-tidy] Add C++ member function support to custom bugprone-unsafe-functions matches (#117165)

Before, C++ member functions in the format of ``Class instance;
instance.memberfn();`` were unable to be matched.
This PR adds support for this type of call, and it is matched in exactly
the same format as other functions (eg. ``::Class::memberfn`` qualified
name).

Author: Discookie

clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp

@@ -256,13 +256,32 @@ void UnsafeFunctionsCheck::registerMatchers(MatchFinder *Finder) {
                                           .bind(CustomFunctionNamesId)))
                            .bind(DeclRefId),
                        this);
+    // C++ member calls do not contain a DeclRefExpr to the function decl.
+    // Instead, they contain a MemberExpr that refers to the decl.
+    Finder->addMatcher(memberExpr(member(functionDecl(CustomFunctionsMatcher)
+                                             .bind(CustomFunctionNamesId)))
+                           .bind(DeclRefId),
+                       this);
   }
 }
 
 void UnsafeFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
-  const auto *DeclRef = Result.Nodes.getNodeAs<DeclRefExpr>(DeclRefId);
-  const auto *FuncDecl = cast<FunctionDecl>(DeclRef->getDecl());
-  assert(DeclRef && FuncDecl && "No valid matched node in check()");
+  const Expr *SourceExpr;
+  const FunctionDecl *FuncDecl;
+
+  if (const auto *DeclRef = Result.Nodes.getNodeAs<DeclRefExpr>(DeclRefId)) {
+    SourceExpr = DeclRef;
+    FuncDecl = cast<FunctionDecl>(DeclRef->getDecl());
+  } else if (const auto *Member =
+                 Result.Nodes.getNodeAs<MemberExpr>(DeclRefId)) {
+    SourceExpr = Member;
+    FuncDecl = cast<FunctionDecl>(Member->getMemberDecl());
+  } else {
+    llvm_unreachable("No valid matched node in check()");
+    return;
+  }
+
+  assert(SourceExpr && FuncDecl && "No valid matched node in check()");
 
   // Only one of these are matched at a time.
   const auto *AnnexK = Result.Nodes.getNodeAs<FunctionDecl>(
@@ -286,14 +305,15 @@ void UnsafeFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
             Entry.Reason.empty() ? "is marked as unsafe" : Entry.Reason.c_str();
 
         if (Entry.Replacement.empty()) {
-          diag(DeclRef->getExprLoc(), "function %0 %1; it should not be used")
+          diag(SourceExpr->getExprLoc(),
+               "function %0 %1; it should not be used")
               << FuncDecl << Reason << Entry.Replacement
-              << DeclRef->getSourceRange();
+              << SourceExpr->getSourceRange();
         } else {
-          diag(DeclRef->getExprLoc(),
+          diag(SourceExpr->getExprLoc(),
                "function %0 %1; '%2' should be used instead")
               << FuncDecl << Reason << Entry.Replacement
-              << DeclRef->getSourceRange();
+              << SourceExpr->getSourceRange();
         }
 
         return;
@@ -323,9 +343,9 @@ void UnsafeFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
   if (!ReplacementFunctionName)
     return;
 
-  diag(DeclRef->getExprLoc(), "function %0 %1; '%2' should be used instead")
+  diag(SourceExpr->getExprLoc(), "function %0 %1; '%2' should be used instead")
       << FuncDecl << getRationaleFor(FunctionName)
-      << ReplacementFunctionName.value() << DeclRef->getSourceRange();
+      << ReplacementFunctionName.value() << SourceExpr->getSourceRange();
 }
 
 void UnsafeFunctionsCheck::registerPPCallbacks(

clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.h

@@ -43,7 +43,7 @@ class UnsafeFunctionsCheck : public ClangTidyCheck {
 private:
   const std::vector<CheckedFunction> CustomFunctions;
 
-  // If true, the default set of functions are reported.
+  /// If true, the default set of functions are reported.
   const bool ReportDefaultFunctions;
   /// If true, additional functions from widely used API-s (such as POSIX) are
   /// added to the list of reported functions.

clang-tools-extra/docs/ReleaseNotes.rst

@@ -97,6 +97,10 @@ New check aliases
 Changes in existing checks
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Improved :doc:`bugprone-unsafe-functions
+  <clang-tidy/checks/bugprone/unsafe-functions>` check to allow specifying
+  additional C++ member functions to match.
+
 Removed checks
 ^^^^^^^^^^^^^^
 

clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst

@@ -114,6 +114,17 @@ qualified name (i.e. ``std::original``), otherwise the regex is matched against
 If the regular expression starts with `::` (or `^::`), it is matched against the
 fully qualified name (``::std::original``).
 
+.. note::
+
+   Fully qualified names can contain template parameters on certain C++ classes, but not on C++ functions.
+   Type aliases are resolved before matching.
+
+   As an example, the member function ``open`` in the class ``std::ifstream``
+   has a fully qualified name of ``::std::basic_ifstream<char>::open``.
+
+   The example could also be matched with the regex ``::std::basic_ifstream<[^>]*>::open``, which matches all potential
+   template parameters, but does not match nested template classes.
+
 Options
 -------
 

clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions-custom-regex.cpp

@@ -1,11 +1,19 @@
 // RUN: %check_clang_tidy -check-suffix=NON-STRICT-REGEX         %s bugprone-unsafe-functions %t --\
-// RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: '::name_match,replacement,is a qualname match;^::prefix_match,,is matched on qualname prefix'}}"
+// RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: '::name_match,replacement,is a qualname match;^::prefix_match,,is matched on qualname prefix;^::S::member_match_,,is matched on a C++ class member'}}"
 // RUN: %check_clang_tidy -check-suffix=STRICT-REGEX         %s bugprone-unsafe-functions %t --\
-// RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: '^name_match$,replacement,is matched on function name only;^::prefix_match$,,is a full qualname match'}}"
+// RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: '^name_match$,replacement,is matched on function name only;^::prefix_match$,,is a full qualname match;^::S::member_match_1$,,is matched on a C++ class member'}}"
 
 void name_match();
 void prefix_match();
 
+struct S {
+  static void member_match_1() {}
+  void member_match_2() {}
+};
+
+void member_match_1() {}
+void member_match_unmatched() {}
+
 namespace regex_test {
 void name_match();
 void prefix_match();
@@ -42,3 +50,25 @@ void f1() {
   // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'prefix_match_regex' is matched on qualname prefix; it should not be used
   // no-warning STRICT-REGEX
 }
+
+void f2() {
+  S s;
+
+  S::member_match_1();
+  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'member_match_1' is matched on a C++ class member; it should not be used
+  // CHECK-MESSAGES-STRICT-REGEX: :[[@LINE-2]]:3: warning: function 'member_match_1' is matched on a C++ class member; it should not be used
+
+  s.member_match_1();
+  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:5: warning: function 'member_match_1' is matched on a C++ class member; it should not be used
+  // CHECK-MESSAGES-STRICT-REGEX: :[[@LINE-2]]:5: warning: function 'member_match_1' is matched on a C++ class member; it should not be used
+
+  s.member_match_2();
+  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:5: warning: function 'member_match_2' is matched on a C++ class member; it should not be used
+  // no-warning STRICT-REGEX
+
+  member_match_1();
+  // no-warning
+
+  member_match_unmatched();
+  // no-warning
+}