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* [Bug c++/98326] New: ICE: in create_tmp_var, at gimple-expr.c:482, converting stateless generic-lambda to function pointer
@ 2020-12-16 18:17 leni536 at gmail dot com
  2020-12-17 11:05 ` [Bug c++/98326] [10/11 Regression] ICE: in create_tmp_var, at gimple-expr.c:482, converting stateless generic-lambda to function pointer since r10-599-gc652ff8312433483 marxin at gcc dot gnu.org
                   ` (6 more replies)
  0 siblings, 7 replies; 8+ messages in thread
From: leni536 at gmail dot com @ 2020-12-16 18:17 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98326

            Bug ID: 98326
           Summary: ICE: in create_tmp_var, at gimple-expr.c:482,
                    converting stateless generic-lambda to function
                    pointer
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: leni536 at gmail dot com
  Target Milestone: ---

version: g++ (Compiler-Explorer-Build) 10.2.0
arguments: -O2 -std=c++17 -pedantic-errors

```
struct A {
    A() = default;
    A(const A&) {}
};

void (*fptr)(A) = [](auto){};
```

<source>: In static member function 'static constexpr decltype
(((const<lambda(auto:1)>*)0)->operator()<auto:1>(static_cast<auto:1&&>(<anonymous>)))<lambda(auto:1)>::_FUN(auto:1)
[with auto:1 = A]':
<source>:6:28: internal compiler error: in create_tmp_var, at gimple-expr.c:482
    6 | void (*fptr)(A) = [](auto){};
      |                            ^


The ICE seems to happen when the by-value parameter's type is not trivially
copyable. It can also be reproduced with a non-trivial destructor.

If the copy-constructor is deleted then it fails to compile with a non-ice
error.

Related: PR 86943

In my understanding gcc tries to copy/move the by-value parameter in the free
function to pass it to `closure{}(args)`. I don't think that copying/moving the
by-value argument is correct. The effect of calling the resulting function
pointer should be equivalent to calling the operator() on the closure object,
it's not expressed in terms of forwarding the parameters:

https://timsong-cpp.github.io/cppwp/n4659/expr.prim.lambda.closure#8

It's more precisely spelled out in C++20, as there it can be expressed it in
terms of a default constructed object of the closure type:

http://eel.is/c++draft/expr.prim.lambda.closure#10.sentence-1

^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2021-02-12  2:50 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-12-16 18:17 [Bug c++/98326] New: ICE: in create_tmp_var, at gimple-expr.c:482, converting stateless generic-lambda to function pointer leni536 at gmail dot com
2020-12-17 11:05 ` [Bug c++/98326] [10/11 Regression] ICE: in create_tmp_var, at gimple-expr.c:482, converting stateless generic-lambda to function pointer since r10-599-gc652ff8312433483 marxin at gcc dot gnu.org
2021-01-04 15:30 ` rguenth at gcc dot gnu.org
2021-02-03 13:22 ` jakub at gcc dot gnu.org
2021-02-08 21:15 ` jason at gcc dot gnu.org
2021-02-09  1:52 ` cvs-commit at gcc dot gnu.org
2021-02-12  2:30 ` cvs-commit at gcc dot gnu.org
2021-02-12  2:50 ` jason at gcc dot gnu.org

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