[analyzer] NFC: CallDescription: Implement describing C library functions.

When matching C standard library functions in the checker, it's easy to forget
that they are often implemented as macros that are expanded to builtins.

Such builtins would have a different name, so matching the callee identifier
would fail, or may sometimes have more arguments than expected, so matching
the exact number of arguments would fail, but this is fine as long as we have
all the arguments that we need in their respective places.

This patch adds a set of flags to the CallDescription class so that to handle
various special matching rules, and adds the first flag into this set,
which enables a more fuzzy matching for functions that
may be implemented as compiler builtins.

Differential Revision: https://reviews.llvm.org/D62556

llvm-svn: 364867

1 files changed, 17 insertions, 5 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/CallEvent.cpp b/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
index 6339423f112..81a9ee4d90b 100644
--- a/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
+++ b/clang/lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -356,20 +356,32 @@ bool CallEvent::isCalled(const CallDescription &CD) const {
   // FIXME: Add ObjC Message support.
   if (getKind() == CE_ObjCMessage)
     return false;
+
+  const IdentifierInfo *II = getCalleeIdentifier();
+  if (!II)
+    return false;
+  const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(getDecl());
+  if (!FD)
+    return false;
+
+  if (CD.Flags & CDF_MaybeBuiltin) {
+    return CheckerContext::isCLibraryFunction(FD, CD.getFunctionName()) &&
+           (!CD.RequiredArgs || CD.RequiredArgs <= getNumArgs());
+  }
+
   if (!CD.IsLookupDone) {
     CD.IsLookupDone = true;
     CD.II = &getState()->getStateManager().getContext().Idents.get(
         CD.getFunctionName());
   }
-  const IdentifierInfo *II = getCalleeIdentifier();
-  if (!II || II != CD.II)
+
+  if (II != CD.II)
     return false;
 
-  const Decl *D = getDecl();
   // If CallDescription provides prefix names, use them to improve matching
   // accuracy.
-  if (CD.QualifiedName.size() > 1 && D) {
-    const DeclContext *Ctx = D->getDeclContext();
+  if (CD.QualifiedName.size() > 1 && FD) {
+    const DeclContext *Ctx = FD->getDeclContext();
     // See if we'll be able to match them all.
     size_t NumUnmatched = CD.QualifiedName.size() - 1;
     for (; Ctx && isa<NamedDecl>(Ctx); Ctx = Ctx->getParent()) {