[clang][bytecode] Use in Expr::tryEvaluateString (llvm#160118)

Fixes llvm#157492

Author: tbaederr

clang/lib/AST/ByteCode/Context.cpp

@@ -237,6 +237,52 @@ bool Context::evaluateCharRange(State &Parent, const Expr *SizeExpr,
   return evaluateStringRepr(Parent, SizeExpr, PtrExpr, Result);
 }
 
+bool Context::evaluateString(State &Parent, const Expr *E,
+                             std::string &Result) {
+  assert(Stk.empty());
+  Compiler<EvalEmitter> C(*this, *P, Parent, Stk);
+
+  auto PtrRes = C.interpretAsPointer(E, [&](const Pointer &Ptr) {
+    const Descriptor *FieldDesc = Ptr.getFieldDesc();
+    if (!FieldDesc->isPrimitiveArray())
+      return false;
+
+    if (!Ptr.isConst())
+      return false;
+
+    unsigned N = Ptr.getNumElems();
+
+    if (Ptr.elemSize() == 1 /* bytes */) {
+      const char *Chars = reinterpret_cast<const char *>(Ptr.getRawAddress());
+      unsigned Length = strnlen(Chars, N);
+      // Wasn't null terminated.
+      if (N == Length)
+        return false;
+      Result.assign(Chars, Length);
+      return true;
+    }
+
+    PrimType ElemT = FieldDesc->getPrimType();
+    for (unsigned I = Ptr.getIndex(); I != N; ++I) {
+      INT_TYPE_SWITCH(ElemT, {
+        auto Elem = Ptr.elem<T>(I);
+        if (Elem.isZero())
+          return true;
+        Result.push_back(static_cast<char>(Elem));
+      });
+    }
+    // We didn't find a 0 byte.
+    return false;
+  });
+
+  if (PtrRes.isInvalid()) {
+    C.cleanup();
+    Stk.clear();
+    return false;
+  }
+  return true;
+}
+
 bool Context::evaluateStrlen(State &Parent, const Expr *E, uint64_t &Result) {
   assert(Stk.empty());
   Compiler<EvalEmitter> C(*this, *P, Parent, Stk);

clang/lib/AST/ByteCode/Context.h

@@ -67,6 +67,10 @@ class Context final {
   bool evaluateCharRange(State &Parent, const Expr *SizeExpr,
                          const Expr *PtrExpr, std::string &Result);
 
+  /// Evaluate \param E and if it can be evaluated to a null-terminated string,
+  /// copy the result into \param Result.
+  bool evaluateString(State &Parent, const Expr *E, std::string &Result);
+
   /// Evalute \param E and if it can be evaluated to a string literal,
   /// run strlen() on it.
   bool evaluateStrlen(State &Parent, const Expr *E, uint64_t &Result);

clang/lib/AST/ExprConstant.cpp

@@ -18905,9 +18905,15 @@ std::optional<std::string> Expr::tryEvaluateString(ASTContext &Ctx) const {
   uint64_t Result;
   std::string StringResult;
 
+  if (Info.EnableNewConstInterp) {
+    if (!Info.Ctx.getInterpContext().evaluateString(Info, this, StringResult))
+      return std::nullopt;
+    return StringResult;
+  }
+
   if (EvaluateBuiltinStrLen(this, Result, Info, &StringResult))
     return StringResult;
-  return {};
+  return std::nullopt;
 }
 
 template <typename T>

clang/test/SemaCXX/verbose-trap.cpp

@@ -1,6 +1,9 @@
 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -fcxx-exceptions -verify %s
 // RUN: %clang_cc1 -std=c++20 -fsyntax-only -fcxx-exceptions -verify %s
 
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -fcxx-exceptions -verify %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -fcxx-exceptions -verify %s -fexperimental-new-constant-interpreter
+
 #if !__has_builtin(__builtin_verbose_trap)
 #error
 #endif
@@ -45,3 +48,14 @@ void f2() {
 void test() {
   f<constCat3, constMsg3>(nullptr);
 }
+
+/// Arguments must be null terminated.
+int foo() {
+  constexpr char K[] = {'a', 'b'};
+  __builtin_verbose_trap("hehe", K); // expected-error {{argument to __builtin_verbose_trap must be a pointer to a constant string}}
+  __builtin_verbose_trap(K, "hehe"); //expected-error {{argument to __builtin_verbose_trap must be a pointer to a constant string}}
+
+  constexpr char K2[] = {'a', 'b', '\0'};
+  __builtin_verbose_trap("hehe", K2);
+  __builtin_verbose_trap(K2, "hehe");
+}