[PATCH] D67019: [analyzer] pr43179: CallDescription: Check number of parameters as well as number of arguments.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ created this revision.
NoQ added reviewers: dcoughlin, xazax.hun, a_sidorin, rnkovacs, Szelethus, baloghadamsoftware, Charusso.
Herald added subscribers: cfe-commits, dkrupp, donat.nagy, mikhail.ramalho, a.sidorin, szepet.
Herald added a project: clang.
NoQ retitled this revision from "[analyzer] CallDescription: Check number of parameters as well as number of arguments." to "[analyzer] pr43179: CallDescription: Check number of parameters as well as number of arguments.".
NoQ edited the summary of this revision.

This is https://bugs.llvm.org/show_bug.cgi?id=43179.

Most functions that our checkers react upon are not C-style variadic functions, and therefore they have as many actual arguments as they have formal parameters.

However, it's not impossible to define a variadic function with the same name. This will crash any checker that relies on `CallDescription` to check the number of arguments but then silently assumes that the number of parameters is the same.

Change `CallDescription` to check both the number of arguments and the number of parameters by default.

If we're intentionally trying to match variadic functions, allow specifying arguments and parameters separately (possibly omitting any of them). For now we only have one `CallDescription` which would make use of those, namely `__builtin_va_start` itself.


Repository:
  rC Clang

https://reviews.llvm.org/D67019

Files:
  clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
  clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
  clang/lib/StaticAnalyzer/Core/CallEvent.cpp
  clang/test/Analysis/cast-value-weird.cpp


Index: clang/test/Analysis/cast-value-weird.cpp
===================================================================
--- /dev/null
+++ clang/test/Analysis/cast-value-weird.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,apiModeling -verify %s
+
+// expected-no-diagnostics
+
+namespace llvm {
+template <typename>
+void cast(...);
+void a() { cast<int>(int()); } // no-crash
+} // namespace llvm
Index: clang/lib/StaticAnalyzer/Core/CallEvent.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/CallEvent.cpp
+++ clang/lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -368,7 +368,8 @@
 
   if (CD.Flags & CDF_MaybeBuiltin) {
     return CheckerContext::isCLibraryFunction(FD, CD.getFunctionName()) &&
-           (!CD.RequiredArgs || CD.RequiredArgs <= getNumArgs());
+           (!CD.RequiredArgs || CD.RequiredArgs <= getNumArgs()) &&
+           (!CD.RequiredParams || CD.RequiredParams <= parameters().size());
   }
 
   if (!CD.IsLookupDone) {
@@ -407,7 +408,8 @@
       return false;
   }
 
-  return (!CD.RequiredArgs || CD.RequiredArgs == getNumArgs());
+  return (!CD.RequiredArgs || CD.RequiredArgs == getNumArgs()) &&
+         (!CD.RequiredParams || CD.RequiredParams == parameters().size());
 }
 
 SVal CallEvent::getArgSVal(unsigned Index) const {
Index: clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
@@ -116,7 +116,9 @@
         // vswprintf is the wide version of vsnprintf,
         // vsprintf has no wide version
         {{"vswscanf", 3}, 2}};
-const CallDescription ValistChecker::VaStart("__builtin_va_start", 2),
+
+const CallDescription
+    ValistChecker::VaStart("__builtin_va_start", /*Args=*/2, /*Params=*/1),
     ValistChecker::VaCopy("__builtin_va_copy", 2),
     ValistChecker::VaEnd("__builtin_va_end", 1);
 } // end anonymous namespace
Index: clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
===================================================================
--- clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
+++ clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
@@ -1064,8 +1064,19 @@
   // e.g. "{a, b}" represent the qualified names, like "a::b".
   std::vector<const char *> QualifiedName;
   Optional<unsigned> RequiredArgs;
+  Optional<size_t> RequiredParams;
   int Flags;
 
+  // A constructor helper.
+  static Optional<size_t> readRequiredParams(Optional<unsigned> RequiredArgs,
+                                             Optional<size_t> RequiredParams) {
+    if (RequiredParams)
+      return RequiredParams;
+    if (RequiredArgs)
+      return static_cast<size_t>(*RequiredArgs);
+    return None;
+  }
+
 public:
   /// Constructs a CallDescription object.
   ///
@@ -1078,14 +1089,17 @@
   /// call. Omit this parameter to match every occurrence of call with a given
   /// name regardless the number of arguments.
   CallDescription(int Flags, ArrayRef<const char *> QualifiedName,
-                  Optional<unsigned> RequiredArgs = None)
+                  Optional<unsigned> RequiredArgs = None,
+                  Optional<size_t> RequiredParams = None)
       : QualifiedName(QualifiedName), RequiredArgs(RequiredArgs),
+        RequiredParams(readRequiredParams(RequiredArgs, RequiredParams)),
         Flags(Flags) {}
 
   /// Construct a CallDescription with default flags.
   CallDescription(ArrayRef<const char *> QualifiedName,
-                  Optional<unsigned> RequiredArgs = None)
-      : CallDescription(0, QualifiedName, RequiredArgs) {}
+                  Optional<unsigned> RequiredArgs = None,
+                  Optional<size_t> RequiredParams = None)
+      : CallDescription(0, QualifiedName, RequiredArgs, RequiredParams) {}
 
   /// Get the name of the function that this object matches.
   StringRef getFunctionName() const { return QualifiedName.back(); }


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