https://issues.dlang.org/show_bug.cgi?id=23112

Susan <su+dlangissues@angel-island.zone> changed:

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https://issues.dlang.org/show_bug.cgi?id=23112

Dennis <dkorpel@live.nl> changed:

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                 CC|                            |dkorpel@live.nl

--- Comment #1 from Dennis <dkorpel@live.nl> ---
An uninstantiated template generates no code, so here's the test modified a
bit:
```
 struct Forward(alias F)
 {
    auto call()()
    {
        return F();
    }
}

auto bar(int a) @nogc nothrow @safe
{
    auto f()
    {
        return a;
    }
    return Forward!f();
}

extern(C) void main() @nogc
{
    assert(bar(3).call() == 3);
}

```

Compile with -betterC and you get: undefined reference to '_d_allocmemory'

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https://issues.dlang.org/show_bug.cgi?id=23112

Walter Bright <bugzilla@digitalmars.com> changed:

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           Keywords|                            |betterC
                 CC|                            |bugzilla@digitalmars.com

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https://issues.dlang.org/show_bug.cgi?id=23112

--- Comment #2 from Walter Bright <bugzilla@digitalmars.com> ---
(In reply to Dennis from comment #1)
>     auto call()()

Rewriting as:

>     auto call()

and it gives the error:

test2.d(8): Error: function `test2.bar` is `@nogc` yet allocates closures with
the GC
test2.d(10):        test2.bar.f closes over variable a at test2.d(8)

which is what we expect. The trouble with the template version is the
semantic3() of bar() should run the semantic3() of Forward.call, which is
necessary to discover that bar() requires a closure. But it does not do the
semantic3() of Forward.call until after semantic3() for bar() has completed.

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https://issues.dlang.org/show_bug.cgi?id=23112

Walter Bright <bugzilla@digitalmars.com> changed:

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https://issues.dlang.org/show_bug.cgi?id=23112

--- Comment #3 from Walter Bright <bugzilla@digitalmars.com> ---
Some further study.

The semantic analysis for call()() cannot be done during the semantic analysis
for bar() or Forward, because the template arguments to call()() are as yet
unknown. We only find out the arguments when main() takes the return value (an
instance of Forward) and calls it.

To fix this, the argument `f` supplied to the parameter `alias F` of `Forward` must be regarded as escaping when the instance of `Forward` is returned from `bar()`.

Not doing this is a major hole in the @safe system.

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https://issues.dlang.org/show_bug.cgi?id=23112

Walter Bright <bugzilla@digitalmars.com> changed:

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           See Also|                            |https://issues.dlang.org/sh
                   |                            |ow_bug.cgi?id=23160

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https://issues.dlang.org/show_bug.cgi?id=23112

--- Comment #4 from Walter Bright <bugzilla@digitalmars.com> ---
A simpler version of this is filed as https://issues.dlang.org/show_bug.cgi?id=23160 which should be fixed first.

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https://issues.dlang.org/show_bug.cgi?id=23112

Dlang Bot <dlang-bot@dlang.rocks> changed:

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--- Comment #5 from Dlang Bot <dlang-bot@dlang.rocks> ---
@WalterBright created dlang/dmd pull request #14183 "fix Issue 23112 - code passes @nogc, allocates anyway" fixing this issue:

- fix Issue 23112 - code passes @nogc, allocates anyway

https://github.com/dlang/dmd/pull/14183

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https://issues.dlang.org/show_bug.cgi?id=23112

Walter Bright <bugzilla@digitalmars.com> changed:

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           See Also|                            |https://issues.dlang.org/sh
                   |                            |ow_bug.cgi?id=14730

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