[PATCH] D138914: Make evaluation of nested requirement consistent with requires expr.

[Utkarsh Saxena via Phabricator via cfe-commits]

usaxena95 marked an inline comment as done.
usaxena95 added inline comments.


================
Comment at: clang/lib/Sema/SemaTemplateInstantiate.cpp:2339
+            Req->getConstraintExpr()->getSourceRange(), Satisfaction))
+      TransConstraint = Result[0];
+    assert(!Trap.hasErrorOccurred() && "Substitution failures must be handled "
----------------
rtrieu wrote:
> I have found a crash here when it access vector `Result` without checking the size first, leading to out of bounds memory access.  CReduce gave the following testcase:
> 
> ```
> template <class a, a> struct b;
> template <bool c> using d = b<bool, c>;
> template <class a, class e> using f = d<__is_same(a, e)>;
> template <class a, class e>
> concept g = f<a, e>::h;
> template <class a, class e>
> concept i = g<e, a>;
> template <typename> class j {
>   template <typename k>
>   requires requires { requires i<j, k>; }
>   j();
> };
> template <> j();
> ```
> 
> `clang reduce.ii --std=c++20`
> 
> ```
> assertion failed at llvm/include/llvm/ADT/SmallVector.h:294 in reference llvm::SmallVectorTemplateCommon<clang::Expr *>::operator[](size_type) [T = clang::Expr *]: idx < size()
> ...
> ...
> (anonymous namespace)::TemplateInstantiator::TransformNestedRequirement(clang::concepts::NestedRequirement*) clang/lib/Sema/SemaTemplateInstantiate.cpp:2339:25
> ...
> ...
> ```
Thanks for noticing and sorry for the trouble. I have fixed this forward in https://github.com/llvm/llvm-project/commit/8c0aa53b07caa604d58a0d83dc571d8fcb004972.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D138914/new/

https://reviews.llvm.org/D138914