[clang] [clang][bytecode] Check memove/memcpy for available elements (PR #121383)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>

Both destination and source pointer need to have at least as many elements as 
requested.

---
Full diff: https://github.com/llvm/llvm-project/pull/121383.diff


2 Files Affected:

- (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+38-15) 
- (modified) clang/test/AST/ByteCode/builtin-functions.cpp (+9) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp 
b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 2ae91feb2d9e8e..d0d8b03deab268 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -17,6 +17,7 @@
 #include "clang/Basic/Builtins.h"
 #include "clang/Basic/TargetBuiltins.h"
 #include "clang/Basic/TargetInfo.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/SipHash.h"
 
 namespace clang {
@@ -1837,6 +1838,7 @@ static bool interp__builtin_memcpy(InterpState &S, 
CodePtr OpPC,
   assert(Call->getNumArgs() == 3);
   unsigned ID = Func->getBuiltinID();
   Pointer DestPtr = getParam<Pointer>(Frame, 0);
+  const ASTContext &ASTCtx = S.getASTContext();
   const Pointer &SrcPtr = getParam<Pointer>(Frame, 1);
   const APSInt &Size =
       peekToAPSInt(S.Stk, *S.getContext().classify(Call->getArg(2)));
@@ -1857,34 +1859,55 @@ static bool interp__builtin_memcpy(InterpState &S, 
CodePtr OpPC,
     Pointer DiagPtr = (SrcPtr.isZero() ? SrcPtr : DestPtr);
     S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_memcpy_null)
         << /*IsMove=*/Move << /*IsWchar=*/false << !SrcPtr.isZero()
-        << DiagPtr.toDiagnosticString(S.getASTContext());
+        << DiagPtr.toDiagnosticString(ASTCtx);
     return false;
   }
 
-  QualType ElemType;
-  if (DestPtr.getFieldDesc()->isArray())
-    ElemType = DestPtr.getFieldDesc()->getElemQualType();
-  else
-    ElemType = DestPtr.getType();
+  QualType DestElemType;
+  size_t RemainingDestElems;
+  if (DestPtr.getFieldDesc()->isArray()) {
+    DestElemType = DestPtr.getFieldDesc()->getElemQualType();
+    RemainingDestElems = (DestPtr.getNumElems() - DestPtr.getIndex());
+  } else {
+    DestElemType = DestPtr.getType();
+    RemainingDestElems = 1;
+  }
+  unsigned DestElemSize = 
ASTCtx.getTypeSizeInChars(DestElemType).getQuantity();
 
-  unsigned ElemSize =
-      S.getASTContext().getTypeSizeInChars(ElemType).getQuantity();
-  if (Size.urem(ElemSize) != 0) {
+  if (Size.urem(DestElemSize) != 0) {
     S.FFDiag(S.Current->getSource(OpPC),
              diag::note_constexpr_memcpy_unsupported)
-        << Move << /*IsWchar=*/false << 0 << ElemType << Size << ElemSize;
+        << Move << /*IsWchar=*/false << 0 << DestElemType << Size
+        << DestElemSize;
     return false;
   }
 
   QualType SrcElemType;
-  if (SrcPtr.getFieldDesc()->isArray())
+  size_t RemainingSrcElems;
+  if (SrcPtr.getFieldDesc()->isArray()) {
     SrcElemType = SrcPtr.getFieldDesc()->getElemQualType();
-  else
+    RemainingSrcElems = (SrcPtr.getNumElems() - SrcPtr.getIndex());
+  } else {
     SrcElemType = SrcPtr.getType();
+    RemainingSrcElems = 1;
+  }
+  unsigned SrcElemSize = ASTCtx.getTypeSizeInChars(SrcElemType).getQuantity();
 
-  if (!S.getASTContext().hasSameUnqualifiedType(ElemType, SrcElemType)) {
+  if (!ASTCtx.hasSameUnqualifiedType(DestElemType, SrcElemType)) {
     S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_memcpy_type_pun)
-        << Move << SrcElemType << ElemType;
+        << Move << SrcElemType << DestElemType;
+    return false;
+  }
+
+  // Check if we have enough elements to read from and write to/
+  size_t RemainingDestBytes = RemainingDestElems * DestElemSize;
+  size_t RemainingSrcBytes = RemainingSrcElems * SrcElemSize;
+  if (Size.ugt(RemainingDestBytes) || Size.ugt(RemainingSrcBytes)) {
+    APInt N = Size.udiv(DestElemSize);
+    S.FFDiag(S.Current->getSource(OpPC),
+             diag::note_constexpr_memcpy_unsupported)
+        << Move << /*IsWChar*/ false << (Size.ugt(RemainingSrcBytes) ? 1 : 2)
+        << DestElemType << toString(N, 10, /*Signed=*/false);
     return false;
   }
 
@@ -1905,7 +1928,7 @@ static bool interp__builtin_memcpy(InterpState &S, 
CodePtr OpPC,
   // As a last resort, reject dummy pointers.
   if (DestPtr.isDummy() || SrcPtr.isDummy())
     return false;
-  assert(Size.getZExtValue() % ElemSize == 0);
+  assert(Size.getZExtValue() % DestElemSize == 0);
   if (!DoMemcpy(S, OpPC, SrcPtr, DestPtr, Bytes(Size.getZExtValue()).toBits()))
     return false;
 
diff --git a/clang/test/AST/ByteCode/builtin-functions.cpp 
b/clang/test/AST/ByteCode/builtin-functions.cpp
index c1fd1bc1381503..b0f8ea2e55ee0b 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1244,6 +1244,15 @@ namespace BuiltinMemcpy {
   }
   static_assert(cpyptr());
 
+#ifndef __AVR__
+  constexpr int test_memmove(int a, int b, int n) {
+    int arr[4] = {1, 2, 3, 4};
+    __builtin_memmove(arr + a, arr + b, n); // both-note {{destination is not 
a contiguous array of at least 3 elements of type 'int'}}
+    return result(arr);
+  }
+  static_assert(test_memmove(2, 0, 12) == 4234); // both-error {{constant}} \
+                                                 // both-note {{in call}}
+#endif
 }
 
 namespace Memcmp {

``````````

</details>


https://github.com/llvm/llvm-project/pull/121383
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