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Unable to use std::initializer_list in constant expressions #15489

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DougGregor opened this issue Jan 30, 2013 · 5 comments
Closed

Unable to use std::initializer_list in constant expressions #15489

DougGregor opened this issue Jan 30, 2013 · 5 comments
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bugzilla Issues migrated from bugzilla c++11

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@DougGregor
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Bugzilla Link 15117
Resolution FIXED
Resolved on Jun 12, 2013 17:32
Version trunk
OS All
CC @DougGregor,@zygoloid

Extended Description

The following is well-formed:

#include <initializer_list>
constexpr auto foo{1, 2};

but Clang rejects it with

t2.cpp:3:16: error: constexpr variable 'foo' must be initialized by a constant
expression
constexpr auto foo{1, 2};
^ ~~~~~~

because RecordExprEvaluator::VisitInitListExpr doesn't handle std::initializer_lists. What it should do is create an array and then set the pointer/length fields of the std::initializer_list to point into that array.
@DougGregor
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This is also rdar://problem/13096001.

@zygoloid
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Mannequin

zygoloid mannequin commented Jan 30, 2013

This was ill-formed in FDIS (initializer_list wasn't a literal type). I guess LWG are adding core language features now? :)

@DougGregor
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Sneaky, eh?

@zygoloid
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Mannequin

zygoloid mannequin commented Jan 31, 2013

Ugh, our current constant value representation can't handle this in the case where the initializer_list initialization creates additional unnamed static-storage-duration arrays.

We have a similar problem for nested initializer_list objects outside the constant expression evaluator:

:2:56: error: cannot compile this nested global std::initializer_list yet
std::initializer_list<std::initializer_list> x = {{1,2},{3,4,5}};
^~~~~

@zygoloid
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Mannequin

zygoloid mannequin commented Jun 13, 2013

Fixed in r183872.

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 4, 2021
This issue was closed.
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@DougGregor