[analyzer] Tweak MallocSizeOfChecker to not warn when using sizeof(void*) to allocate a bunch of any pointer type.

This suppresses a common false positive when analyzing libc++.

Along the way, introduce some tests to show this checker actually
works with C++ static_cast<>.

llvm-svn: 220160

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/MallocSizeofChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/MallocSizeofChecker.cpp
index 4a50d936287..296aec66805 100644
--- a/clang/lib/StaticAnalyzer/Checkers/MallocSizeofChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/MallocSizeofChecker.cpp
@@ -137,6 +137,10 @@ public:
 // Determine if the pointee and sizeof types are compatible.  Here
 // we ignore constness of pointer types.
 static bool typesCompatible(ASTContext &C, QualType A, QualType B) {
+  // sizeof(void*) is compatible with any other pointer.
+  if (B->isVoidPointerType() && A->getAs<PointerType>())
+    return true;
+
   while (true) {
     A = A.getCanonicalType();
     B = B.getCanonicalType();