[clang] [clang][bytecode][NFC] Add assert to ptrauth_string_discriminator (PR #132527)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>

As pointed out by @<!-- -->shafik, this confuses static analysis and most probably humans as well. Add an assertion to ensure the given array has at least one element.

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Full diff: https://github.com/llvm/llvm-project/pull/132527.diff


1 Files Affected:

- (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+3) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 57037b674feba..a6e1884404287 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1477,6 +1477,9 @@ static bool interp__builtin_ptrauth_string_discriminator(
   const auto &Ptr = S.Stk.peek<Pointer>();
   assert(Ptr.getFieldDesc()->isPrimitiveArray());
 
+  // This should be created for a StringLiteral, so should alway shold at least
+  // one array element.
+  assert(Ptr.getFieldDesc()->getNumElems() >= 1);
   StringRef R(&Ptr.deref<char>(), Ptr.getFieldDesc()->getNumElems() - 1);
   uint64_t Result = getPointerAuthStableSipHash(R);
   pushInteger(S, Result, Call->getType());

``````````

</details>


https://github.com/llvm/llvm-project/pull/132527