[analyzer] Support C++17 aggregates with bases without constructors.

RegionStore now knows how to bind a nonloc::CompoundVal that represents the
value of an aggregate initializer when it has its initial segment of sub-values
correspond to base classes.

Additionally, fixes the crash from pr40022.

Differential Revision: https://reviews.llvm.org/D59054

llvm-svn: 356222

clang/lib/StaticAnalyzer/Core/RegionStore.cpp

@@ -2334,12 +2334,57 @@ RegionBindingsRef RegionStoreManager::bindStruct(RegionBindingsConstRef B,
   if (V.isUnknown() || !V.getAs<nonloc::CompoundVal>())
     return bindAggregate(B, R, UnknownVal());
 
+  // The raw CompoundVal is essentially a symbolic InitListExpr: an (immutable)
+  // list of other values. It appears pretty much only when there's an actual
+  // initializer list expression in the program, and the analyzer tries to
+  // unwrap it as soon as possible.
+  // This code is where such unwrap happens: when the compound value is put into
+  // the object that it was supposed to initialize (it's an *initializer* list,
+  // after all), instead of binding the whole value to the whole object, we bind
+  // sub-values to sub-objects. Sub-values may themselves be compound values,
+  // and in this case the procedure becomes recursive.
+  // FIXME: The annoying part about compound values is that they don't carry
+  // any sort of information about which value corresponds to which sub-object.
+  // It's simply a list of values in the middle of nowhere; we expect to match
+  // them to sub-objects, essentially, "by index": first value binds to
+  // the first field, second value binds to the second field, etc.
+  // It would have been much safer to organize non-lazy compound values as
+  // a mapping from fields/bases to values.
   const nonloc::CompoundVal& CV = V.castAs<nonloc::CompoundVal>();
   nonloc::CompoundVal::iterator VI = CV.begin(), VE = CV.end();
 
-  RecordDecl::field_iterator FI, FE;
   RegionBindingsRef NewB(B);
 
+  // In C++17 aggregates may have base classes, handle those as well.
+  // They appear before fields in the initializer list / compound value.
+  if (const auto *CRD = dyn_cast<CXXRecordDecl>(RD)) {
+    assert(CRD->isAggregate() &&
+           "Non-aggregates are constructed with a constructor!");
+
+    for (const auto &B : CRD->bases()) {
+      // (Multiple inheritance is fine though.)
+      assert(!B.isVirtual() && "Aggregates cannot have virtual base classes!");
+
+      if (VI == VE)
+        break;
+
+      QualType BTy = B.getType();
+      assert(BTy->isStructureOrClassType() && "Base classes must be classes!");
+
+      const CXXRecordDecl *BRD = BTy->getAsCXXRecordDecl();
+      assert(BRD && "Base classes must be C++ classes!");
+
+      const CXXBaseObjectRegion *BR =
+          MRMgr.getCXXBaseObjectRegion(BRD, R, /*IsVirtual=*/false);
+
+      NewB = bindStruct(NewB, BR, *VI);
+
+      ++VI;
+    }
+  }
+
+  RecordDecl::field_iterator FI, FE;
+
   for (FI = RD->field_begin(), FE = RD->field_end(); FI != FE; ++FI) {
 
     if (VI == VE)

clang/test/Analysis/array-struct-region.cpp

@@ -1,7 +1,21 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core,debug.ExprInspection -verify -x c %s
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core,debug.ExprInspection -verify -x c++ -analyzer-config c++-inlining=constructors %s
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core,debug.ExprInspection -DINLINE -verify -x c %s
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core,debug.ExprInspection -DINLINE -verify -x c++ -analyzer-config c++-inlining=constructors %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core\
+// RUN:                    -analyzer-checker=debug.ExprInspection -verify\
+// RUN:                    -x c %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core\
+// RUN:                    -analyzer-checker=debug.ExprInspection -verify\
+// RUN:                    -x c++ -std=c++14 %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core\
+// RUN:                    -analyzer-checker=debug.ExprInspection -verify\
+// RUN:                    -x c++ -std=c++17 %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core\
+// RUN:                    -analyzer-checker=debug.ExprInspection -verify\
+// RUN:                    -DINLINE -x c %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core\
+// RUN:                    -analyzer-checker=debug.ExprInspection -verify\
+// RUN:                    -DINLINE -x c++ -std=c++14 %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core\
+// RUN:                    -analyzer-checker=debug.ExprInspection -verify\
+// RUN:                    -DINLINE -x c++ -std=c++17 %s
 
 void clang_analyzer_eval(int);
 
@@ -196,4 +210,49 @@ namespace EmptyClass {
   }
 }
 
+#if __cplusplus >= 201703L
+namespace aggregate_inheritance_cxx17 {
+struct A {
+  int x;
+};
+
+struct B {
+  int y;
+};
+
+struct C: B {
+  int z;
+};
+
+struct D: A, C {
+  int w;
+};
+
+void foo() {
+  D d{1, 2, 3, 4};
+  clang_analyzer_eval(d.x == 1); // expected-warning{{TRUE}}
+  clang_analyzer_eval(d.y == 2); // expected-warning{{TRUE}}
+  clang_analyzer_eval(d.z == 3); // expected-warning{{TRUE}}
+  clang_analyzer_eval(d.w == 4); // expected-warning{{TRUE}}
+}
+} // namespace aggregate_inheritance_cxx17
+#endif
+
+namespace flex_array_inheritance_cxx17 {
+struct A {
+  int flexible_array[];
+};
+
+struct B {
+  long cookie;
+};
+
+struct C : B {
+  A a;
+};
+
+void foo() {
+  C c{}; // no-crash
+}
+} // namespace flex_array_inheritance_cxx17
 #endif