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[Clang][Sema] Fix wrong initialization kind when handling initializing structured bindings from an array with direct-list-initialization #124793

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Merged
merged 6 commits into from
Feb 8, 2025
Merged

[Clang][Sema] Fix wrong initialization kind when handling initializing structured bindings from an array with direct-list-initialization #124793

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16596ad
Fix wrong initialization kind
zwuis Jan 28, 2025
ad033c9
Make tests more clear
zwuis Jan 29, 2025
88f702e
Add assertion
zwuis Feb 4, 2025
8d6b58e
Add release note
zwuis Feb 4, 2025
c8a84df
Merge branch 'main' into fix-wrong-init-kind
zwuis Feb 4, 2025
3c2a989
Merge branch 'main' into fix-wrong-init-kind
zwuis Feb 8, 2025
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5 changes: 3 additions & 2 deletions clang/lib/Sema/SemaInit.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4861,8 +4861,9 @@ static void TryListInitialization(Sema &S,
S.Context.hasSameUnqualifiedType(SubInit[0]->getType(), DestType) &&
"Deduced to other type?");
TryArrayCopy(S,
InitializationKind::CreateCopy(Kind.getLocation(),
InitList->getLBraceLoc()),
InitializationKind::CreateDirect(Kind.getLocation(),
InitList->getLBraceLoc(),
InitList->getRBraceLoc()),
Comment on lines +4869 to +4871
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@cor3ntin cor3ntin Jan 28, 2025

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and each element is copy-initialized or direct-initialized from the corresponding element of the assignment-expression as specified by the form of the initializer. Otherwise, e is defined as-if by

So I think

auto [_]{a}; // direct-initialization
auto [_](a); // copy-initializer

Is my understanding correct that we need that we need to look at Kind.getKind() and call either CreateCopy or CreateDirect?

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@Endilll Endilll Jan 28, 2025

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I think your understanding is correct.

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@shafik shafik Jan 28, 2025

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This looks correct to me as well, can we come up w/ a test case where it makes a difference though.

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@zwuis zwuis Jan 29, 2025

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... Is my understanding correct that we need that we need to look at Kind.getKind() and call either CreateCopy or CreateDirect?

This part of code is in function trylistinitialization. The function handles list-initialization (for structured bindings, it must be direct-list-initialization here) only.

This looks correct to me as well, can we come up w/ a test case where it makes a difference though.

I believe I have added these tests. I will make these tests more clear.

Entity, SubInit[0], DestType, Sequence,
TreatUnavailableAsInvalid);
if (Sequence)
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21 changes: 10 additions & 11 deletions clang/test/SemaCXX/cxx1z-decomposition.cpp
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Expand Up @@ -200,38 +200,37 @@ namespace lambdas {

namespace by_value_array_copy {
struct explicit_copy {
explicit_copy() = default; // expected-note 2{{candidate constructor not viable: requires 0 arguments, but 1 was provided}}
explicit explicit_copy(const explicit_copy&) = default; // expected-note 2{{explicit constructor is not a candidate}}
explicit_copy() = default; // expected-note {{candidate constructor not viable: requires 0 arguments, but 1 was provided}}
explicit explicit_copy(const explicit_copy&) = default; // expected-note {{explicit constructor is not a candidate}}
};

constexpr int direct_initialization_for_elements() {
explicit_copy ec_arr[2];
auto [a1, b1](ec_arr);
auto [a2, b2]{ec_arr};

int arr[3]{1, 2, 3};
auto [a2, b2, c2](arr);
auto [a3, b3, c3](arr);
auto [a4, b4, c4]{arr}; // GH31813
arr[0]--;
return a2 + b2 + c2 + arr[0];
return a3 + b3 + c3 + a4 + b4 + c4 + arr[0];
}
static_assert(direct_initialization_for_elements() == 6);
static_assert(direct_initialization_for_elements() == 12);

constexpr int copy_initialization_for_elements() {
int arr[2]{4, 5};
auto [a1, b1] = arr;
auto [a2, b2]{arr}; // GH31813
arr[0] = 0;
return a1 + b1 + a2 + b2 + arr[0];
return a1 + b1 + arr[0];
}
static_assert(copy_initialization_for_elements() == 18);
static_assert(copy_initialization_for_elements() == 9);

void copy_initialization_for_elements_with_explicit_copy_ctor() {
explicit_copy ec_arr[2];
auto [a1, b1] = ec_arr; // expected-error {{no matching constructor for initialization of 'explicit_copy[2]'}}
auto [a2, b2]{ec_arr}; // expected-error {{no matching constructor for initialization of 'explicit_copy[2]'}}

// Test prvalue
using T = explicit_copy[2];
auto [a3, b3] = T{};
auto [a4, b4]{T{}};
auto [a2, b2] = T{};
}
} // namespace by_value_array_copy