[Static Analyzer] Structured binding to data members

Introducing structured binding to data members.

Differential Revision: https://reviews.llvm.org/D127643

clang/lib/StaticAnalyzer/Core/ExprEngine.cpp

@@ -2591,9 +2591,22 @@ void ExprEngine::VisitCommonDeclRefExpr(const Expr *Ex, const NamedDecl *D,
     // operator&.
     return;
   }
-  if (isa<BindingDecl>(D)) {
+  if (const auto *BD = dyn_cast<BindingDecl>(D)) {
-    // FIXME: proper support for bound declarations.
+    const auto *DD = cast<DecompositionDecl>(BD->getDecomposedDecl());
-    // For now, let's just prevent crashing.
+
+    if (const auto *ME = dyn_cast<MemberExpr>(BD->getBinding())) {
+      const auto *Field = cast<FieldDecl>(ME->getMemberDecl());
+
+      SVal Base = state->getLValue(DD, LCtx);
+      if (DD->getType()->isReferenceType()) {
+        Base = state->getSVal(Base.getAsRegion());
+      }
+
+      SVal V = state->getLValue(Field, Base);
+
+      Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V));
+    }
+
     return;
   }
 

clang/test/Analysis/uninit-structured-binding-struct.cpp

@@ -0,0 +1,116 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -std=c++17 -verify %s
+
+void clang_analyzer_eval(bool);
+
+struct s {
+  int a;
+  int b;
+};
+
+void a(void) {
+  s tst;
+
+  auto [i, j] = tst;
+
+  int x = i; // expected-warning{{Assigned value is garbage or undefined}}
+}
+
+void b(void) {
+  s tst;
+  tst.a = 1;
+
+  auto [i, j] = tst;
+
+  clang_analyzer_eval(i == 1); // expected-warning{{TRUE}}
+  int y = j;                   // expected-warning{{Assigned value is garbage or undefined}}
+}
+
+void c(void) {
+  s tst;
+
+  auto &[i, j] = tst;
+
+  int x = i; // expected-warning{{Assigned value is garbage or undefined}}
+}
+
+void d(void) {
+  s tst;
+  tst.a = 1;
+
+  auto &[i, j] = tst;
+
+  clang_analyzer_eval(i == 1); // expected-warning{{TRUE}}
+  i = 2;
+  clang_analyzer_eval(tst.a == 2); // expected-warning{{TRUE}}
+
+  int y = j; // expected-warning{{Assigned value is garbage or undefined}}
+}
+
+void e(void) {
+  s tst;
+  tst.a = 1;
+
+  auto &[i, j] = tst;
+
+  clang_analyzer_eval(i == 1); // expected-warning{{TRUE}}
+
+  tst.b = 2;
+  clang_analyzer_eval(j == 2); // expected-warning{{TRUE}}
+}
+
+void f(void) {
+  s tst;
+
+  auto &&[i, j] = tst;
+
+  int x = i; // expected-warning{{Assigned value is garbage or undefined}}
+}
+
+void g(void) {
+  s tst;
+  tst.a = 1;
+
+  auto &&[i, j] = tst;
+
+  clang_analyzer_eval(i == 1); // expected-warning{{TRUE}}
+  int y = j;                   // expected-warning{{Assigned value is garbage or undefined}}
+}
+
+struct s2 {
+  int a = 1;
+  int b = 2;
+};
+
+struct s3 {
+  s x;
+  s2 y;
+};
+
+void h(void) {
+  s3 tst;
+
+  clang_analyzer_eval(tst.y.a == 1); // expected-warning{{TRUE}}
+
+  auto [i, j] = tst;
+
+  // FIXME: These should be undefined, but we have to fix
+  // reading undefined from lazy compound values first.
+  clang_analyzer_eval(i.a); // expected-warning{{UNKNOWN}}
+  clang_analyzer_eval(i.b); // expected-warning{{UNKNOWN}}
+
+  clang_analyzer_eval(j.a == 1); // expected-warning{{TRUE}}
+  clang_analyzer_eval(j.b == 2); // expected-warning{{TRUE}}
+}
+
+void i(void) {
+  s3 tst;
+
+  clang_analyzer_eval(tst.y.a == 1); // expected-warning{{TRUE}}
+
+  auto &[i, j] = tst;
+  j.a = 3;
+
+  clang_analyzer_eval(tst.y.a == 3); // expected-warning{{TRUE}}
+  clang_analyzer_eval(tst.y.b == 2); // expected-warning{{TRUE}}
+  clang_analyzer_eval(j.b == 2);     // expected-warning{{TRUE}}
+}