Re: [PATCH] rust: Fix up aarch64-linux bootstrap [PR106072]

[Arthur Cohen]

Hi Jakub,

On 12/14/22 10:14, Jakub Jelinek via Gcc-rust wrote:

Hi!

Bootstrap fails on aarch64-linux and some other arches with:
.../gcc/rust/parse/rust-parse-impl.h: In member function ‘Rust::AST::ClosureParam 
Rust::Parser<ManagedTokenSource>::parse_closure_param() [with 
ManagedTokenSource = Rust::Lexer]’:
.../gcc/rust/parse/rust-parse-impl.h:8916:49: error: ‘this’ pointer is null 
[-Werror=nonnull]
The problem is that while say on x86_64-linux the side-effects in the
arguments are evaluated from last argument to first, on aarch64-linux
it is the other way around, from first to last.  The C++ I believe even
in C++17 makes the evaluation of those side-effects unordered
(indeterminately sequenced with no interleaving), so that is fine.
But, when the call in return statement is evaluated from first to
last, std::move (pattern) happens before pattern->get_locus () and
the former will make pattern (std::unique_ptr) a wrapper object around
nullptr, so dereferencing it later to call get_locus () on it is invalid.

The following patch fixes that, ok for trunk?

2022-12-14  Jakub Jelinek  <ja...@redhat.com>

        PR rust/106072
        * parse/rust-parse-impl.h (parse_closure_param): Store
        pattern->get_locus () in a temporary before std::move (pattern) is
        invoked.

--- gcc/rust/parse/rust-parse-impl.h.jj 2022-12-13 16:50:12.708093521 +0100
+++ gcc/rust/parse/rust-parse-impl.h    2022-12-14 09:50:31.731111932 +0100
@@ -8912,8 +8912,9 @@ Parser<ManagedTokenSource>::parse_closur
        }
      }

-                           std::move (type), std::move (outer_attrs));
+  Location loc = pattern->get_locus ();
+  return AST::ClosureParam (std::move (pattern), loc, std::move (type),
+                           std::move (outer_attrs));
  }


        Jakub

- return AST::ClosureParam (std::move (pattern), pattern->get_locus (), // Parses a grouped or tuple expression (disambiguates).

https://github.com/Rust-GCC/gccrs/pull/1619





All the best,

--
Arthur Cohen <arthur.co...@embecosm.com>

Toolchain Engineer

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Thanks :) this looks good to me. We already have that issue fixed in our upstream dev branch, by this PR: but we have yet to update GCC's master with our upstream dev branch, so in the meantime feel free to apply your patch. When I'll get to updating master, I'm expecting these kinds of tiny conflicts and we'll deal with them. Thanks a lot for working on this and sorry that my tardiness in updating has caused a duplication of efforts.

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