[analyzer] pr43179: Make CallDescription defensive against C variadic functions.

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 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.

Differential Revision: https://reviews.llvm.org/D67019

llvm-svn: 371256

4 files changed, 33 insertions, 6 deletions

diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
index b2826a81f40..8d1a672bc61 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
@@ -1064,8 +1064,19 @@ class CallDescription {
   // 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 @@ public:
   /// 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(); }
diff --git a/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
index 7e3ce6874b2..9f3b16a5a34 100644
--- a/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
@@ -116,7 +116,9 @@ const SmallVector<ValistChecker::VAListAccepter, 15>
         // 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
diff --git a/clang/lib/StaticAnalyzer/Core/CallEvent.cpp b/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
index 7226ccb4d75..b5d8599012a 100644
--- a/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
+++ b/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -368,7 +368,8 @@ bool CallEvent::isCalled(const CallDescription &CD) const {
 
   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 @@ bool CallEvent::isCalled(const CallDescription &CD) const {
       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 {
diff --git a/clang/test/Analysis/cast-value-weird.cpp b/clang/test/Analysis/cast-value-weird.cpp
new file mode 100644
index 00000000000..f15cc19c447
--- /dev/null
+++ b/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