From 9ac2b8965264a7f20a3e07c913b25c375a080c0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder@redhat.com>
Date: Sun, 14 Jul 2024 21:24:21 +0200
Subject: [PATCH] [clang][Interp] Diagnose volatile reads

---
 clang/lib/AST/Interp/Interp.cpp    | 23 +++++++++++++++++++++++
 clang/test/AST/Interp/literals.cpp |  6 ++++++
 2 files changed, 29 insertions(+)

diff --git a/clang/lib/AST/Interp/Interp.cpp b/clang/lib/AST/Interp/Interp.cpp
index 70a470021e7f22..7b2c0480f80ae5 100644
--- a/clang/lib/AST/Interp/Interp.cpp
+++ b/clang/lib/AST/Interp/Interp.cpp
@@ -444,6 +444,27 @@ bool CheckMutable(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   return false;
 }
 
+bool CheckVolatile(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
+                   AccessKinds AK) {
+  assert(Ptr.isLive());
+
+  // FIXME: This check here might be kinda expensive. Maybe it would be better
+  // to have another field in InlineDescriptor for this?
+  if (!Ptr.isBlockPointer())
+    return true;
+
+  QualType PtrType = Ptr.getType();
+  if (!PtrType.isVolatileQualified())
+    return true;
+
+  const SourceInfo &Loc = S.Current->getSource(OpPC);
+  if (S.getLangOpts().CPlusPlus)
+    S.FFDiag(Loc, diag::note_constexpr_access_volatile_type) << AK << PtrType;
+  else
+    S.FFDiag(Loc);
+  return false;
+}
+
 bool CheckInitialized(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
                       AccessKinds AK) {
   assert(Ptr.isLive());
@@ -508,6 +529,8 @@ bool CheckLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
     return false;
   if (!CheckMutable(S, OpPC, Ptr))
     return false;
+  if (!CheckVolatile(S, OpPC, Ptr, AK))
+    return false;
   return true;
 }
 
diff --git a/clang/test/AST/Interp/literals.cpp b/clang/test/AST/Interp/literals.cpp
index af5bcb6d48ae7e..6c214f5a6efa73 100644
--- a/clang/test/AST/Interp/literals.cpp
+++ b/clang/test/AST/Interp/literals.cpp
@@ -1290,3 +1290,9 @@ namespace UnaryOpError {
   }
 }
 #endif
+
+namespace VolatileReads {
+  const volatile int b = 1;
+  static_assert(b, ""); // both-error {{not an integral constant expression}} \
+                        // both-note {{read of volatile-qualified type 'const volatile int' is not allowed in a constant expression}}
+}