[clang] 56131e3 - [clang][bytecode] Diagnose incomplete types more consistently (#153368)

[via cfe-commits]

Author: Timm Baeder
Date: 2025-08-13T10:40:21+02:00
New Revision: 56131e3959de744e994a0a9409b079cab3c549a7

URL: https://github.com/llvm/llvm-project/commit/56131e3959de744e994a0a9409b079cab3c549a7
DIFF: https://github.com/llvm/llvm-project/commit/56131e3959de744e994a0a9409b079cab3c549a7.diff

LOG: [clang][bytecode] Diagnose incomplete types more consistently (#153368)

To match the diagnostics of the current interpreter.

Added: 
    

Modified: 
    clang/lib/AST/ByteCode/InterpBuiltin.cpp
    clang/test/AST/ByteCode/builtin-functions.cpp

Removed: 
    


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diff  --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 307b77846969f..ee2d532551583 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1783,11 +1783,24 @@ static bool interp__builtin_memcpy(InterpState &S, CodePtr OpPC,
   if (DestPtr.isDummy() || SrcPtr.isDummy())
     return false;
 
+  if (DestPtr.getType()->isIncompleteType()) {
+    S.FFDiag(S.Current->getSource(OpPC),
+             diag::note_constexpr_memcpy_incomplete_type)
+        << Move << DestPtr.getType();
+    return false;
+  }
+  if (SrcPtr.getType()->isIncompleteType()) {
+    S.FFDiag(S.Current->getSource(OpPC),
+             diag::note_constexpr_memcpy_incomplete_type)
+        << Move << SrcPtr.getType();
+    return false;
+  }
+
   QualType DestElemType = getElemType(DestPtr);
   if (DestElemType->isIncompleteType()) {
     S.FFDiag(S.Current->getSource(OpPC),
-             diag::note_constexpr_ltor_incomplete_type)
-        << DestElemType;
+             diag::note_constexpr_memcpy_incomplete_type)
+        << Move << DestElemType;
     return false;
   }
 
@@ -1832,16 +1845,6 @@ static bool interp__builtin_memcpy(InterpState &S, CodePtr OpPC,
     return false;
   }
 
-  if (DestElemType->isIncompleteType() ||
-      DestPtr.getType()->isIncompleteType()) {
-    QualType DiagType =
-        DestElemType->isIncompleteType() ? DestElemType : DestPtr.getType();
-    S.FFDiag(S.Current->getSource(OpPC),
-             diag::note_constexpr_memcpy_incomplete_type)
-        << Move << DiagType;
-    return false;
-  }
-
   if (!DestElemType.isTriviallyCopyableType(ASTCtx)) {
     S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_memcpy_nontrivial)
         << Move << DestElemType;
@@ -2030,8 +2033,13 @@ static bool interp__builtin_memchr(InterpState &S, CodePtr OpPC,
     return true;
   }
 
-  if (Ptr.isDummy())
+  if (Ptr.isDummy()) {
+    if (Ptr.getType()->isIncompleteType())
+      S.FFDiag(S.Current->getSource(OpPC),
+               diag::note_constexpr_ltor_incomplete_type)
+          << Ptr.getType();
     return false;
+  }
 
   // Null is only okay if the given size is 0.
   if (Ptr.isZero()) {

diff  --git a/clang/test/AST/ByteCode/builtin-functions.cpp b/clang/test/AST/ByteCode/builtin-functions.cpp
index e554ef41a8d0f..1223cf8bdc74f 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1514,7 +1514,7 @@ namespace Memchr {
   extern struct Incomplete incomplete;
   static_assert(__builtin_memchr(&incomplete, 0, 0u) == nullptr);
   static_assert(__builtin_memchr(&incomplete, 0, 1u) == nullptr); // both-error {{not an integral constant}} \
-                                                                  // ref-note {{read of incomplete type 'struct Incomplete'}}
+                                                                  // both-note {{read of incomplete type 'struct Incomplete'}}
 
   const unsigned char &u1 = 0xf0;
   auto &&i1 = (const signed char []){-128};
@@ -1697,6 +1697,15 @@ namespace WMemMove {
                                                                      // both-note {{source of 'wmemmove' is nullptr}}
   static_assert(__builtin_wmemmove(null, &global, sizeof(wchar_t))); // both-error {{}} \
                                                                      // both-note {{destination of 'wmemmove' is nullptr}}
+
+  // Check that a pointer to an incomplete array is rejected.
+  constexpr int test_address_of_incomplete_array_type() { // both-error {{never produces a constant}}
+    extern int arr[];
+    __builtin_memmove(&arr, &arr, 4 * sizeof(arr[0])); // both-note 2{{cannot constant evaluate 'memmove' between objects of incomplete type 'int[]'}}
+    return arr[0] * 1000 + arr[1] * 100 + arr[2] * 10 + arr[3];
+  }
+  static_assert(test_address_of_incomplete_array_type() == 1234); // both-error {{constant}} \
+                                                                  // both-note {{in call}}
 }
 
 namespace Invalid {