1 //===- TemplateArgumentHasher.h - Hash Template Arguments -------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "clang/AST/TemplateBase.h" 10 11 namespace clang { 12 namespace serialization { 13 14 /// Calculate a stable hash value for template arguments. We guarantee that 15 /// the same template arguments must have the same hashed values. But we don't 16 /// guarantee that the template arguments with the same hashed value are the 17 /// same template arguments. 18 /// 19 /// ODR hashing may not be the best mechanism to hash the template 20 /// arguments. ODR hashing is (or perhaps, should be) about determining whether 21 /// two things are spelled the same way and have the same meaning (as required 22 /// by the C++ ODR), whereas what we want here is whether they have the same 23 /// meaning regardless of spelling. Maybe we can get away with reusing ODR 24 /// hashing anyway, on the basis that any canonical, non-dependent template 25 /// argument should have the same (invented) spelling in every translation 26 /// unit, but it is not sure that's true in all cases. There may still be cases 27 /// where the canonical type includes some aspect of "whatever we saw first", 28 /// in which case the ODR hash can differ across translation units for 29 /// non-dependent, canonical template arguments that are spelled differently 30 /// but have the same meaning. But it is not easy to raise examples. 31 unsigned StableHashForTemplateArguments(llvm::ArrayRef<TemplateArgument> Args); 32 33 } // namespace serialization 34 } // namespace clang 35