[clang][bytecode] __builtin_is_aligned needs a declaration (#188011)

tbaederr · web-flow · commit 69fb96ba659f · 2026-03-23T12:30:10.000+01:00
Reject pointers to expressions.
Also remove the bytecode version of this test.
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1221,12 +1221,23 @@ static bool interp__builtin_is_aligned_up_down(InterpState &S, CodePtr OpPC,
   if (!Ptr.isBlockPointer())
     return false;
 
+  const ValueDecl *PtrDecl = Ptr.getDeclDesc()->asValueDecl();
+  // We need a pointer for a declaration here.
+  if (!PtrDecl) {
+    if (BuiltinOp == Builtin::BI__builtin_is_aligned)
+      S.FFDiag(Call->getArg(0), diag::note_constexpr_alignment_compute)
+          << Alignment;
+    else
+      S.FFDiag(Call->getArg(0), diag::note_constexpr_alignment_adjust)
+          << Alignment;
+    return false;
+  }
+
   // For one-past-end pointers, we can't call getIndex() since it asserts.
   // Use getNumElems() instead which gives the correct index for past-end.
   unsigned PtrOffset =
       Ptr.isElementPastEnd() ? Ptr.getNumElems() : Ptr.getIndex();
-  CharUnits BaseAlignment =
-      S.getASTContext().getDeclAlign(Ptr.getDeclDesc()->asValueDecl());
+  CharUnits BaseAlignment = S.getASTContext().getDeclAlign(PtrDecl);
   CharUnits PtrAlign =
       BaseAlignment.alignmentAtOffset(CharUnits::fromQuantity(PtrOffset));
 
diff --git a/clang/test/AST/ByteCode/builtin-align-cxx.cpp b/clang/test/AST/ByteCode/builtin-align-cxx.cpp
diff --git a/clang/test/SemaCXX/builtin-align-cxx.cpp b/clang/test/SemaCXX/builtin-align-cxx.cpp
@@ -1,5 +1,6 @@
 // C++-specific checks for the alignment builtins
 // RUN: %clang_cc1 -triple=x86_64-unknown-unknown -std=c++11 -o - %s -fsyntax-only -verify
+// RUN: %clang_cc1 -triple=x86_64-unknown-unknown -std=c++11 -o - %s -fsyntax-only -verify -fexperimental-new-constant-interpreter
 
 // Check that we don't crash when using dependent types in __builtin_align:
 template <typename a, a b>
@@ -239,5 +240,11 @@ static_assert(!__builtin_is_aligned(static_cast<unsigned long>(7), static_cast<s
 static_assert(!__builtin_is_aligned(static_cast<signed long>(7), static_cast<unsigned short>(4)), "");
 static_assert(!__builtin_is_aligned(static_cast<unsigned short>(7), static_cast<signed long>(4)), "");
 
+// Check that one-past-end pointers work correctly (GH#178647).
+static_assert(__builtin_align_up(&align32array[128], 4) == align32array + 128, "");
+
 // Check the diagnostic message
 _Alignas(void) char align_void_array[1]; // expected-error {{invalid application of '_Alignas' to an incomplete type 'void'}}
+
+static_assert(!__builtin_is_aligned(&"", 4), ""); // expected-error {{not an integral constant expression}} \
+                                                  // expected-note {{cannot constant evaluate whether run-time alignment is at least 4}}
