[clang] Diagnose dangling references for parenthesized aggregate initialization. (#117690)

Unlike brace initialization, the parenthesized aggregate initialization
in C++20 does not extend the lifet

[clang] Diagnose dangling references for parenthesized aggregate initialization. (#117690)

Unlike brace initialization, the parenthesized aggregate initialization
in C++20 does not extend the lifetime of a temporary object bound to a
reference in an aggreate. This can lead to dangling references:

```
struct A { const int& r; };
A a1(1); // well-formed, but results in a dangling reference.
```

With this patch, clang will diagnose this common dangling issues.

Fixes #101957

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[Clang] Fix some assertions not looking through type sugar (#92299)

Fixes #92284

Co-authored-by: cor3ntin <corentinjabot@gmail.com>

[clang] Fix `static_cast` to array of unknown bound (#96041)

Per P1975R0 an expression like static_cast<U[]>(...) defines the type of
the expression as U[1].

Fixes https://github.com/llvm/llvm-p

[clang] Fix `static_cast` to array of unknown bound (#96041)

Per P1975R0 an expression like static_cast<U[]>(...) defines the type of
the expression as U[1].

Fixes https://github.com/llvm/llvm-project/issues/62863

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"Reapply "[Sema] Fix crash on invalid code with parenthesized aggrega… (#76833)

…te initialization" (#76272)""

With updates the libc++ tests.

This reverts commit 2205d23 and relands
86dc6e1 a

"Reapply "[Sema] Fix crash on invalid code with parenthesized aggrega… (#76833)

…te initialization" (#76272)""

With updates the libc++ tests.

This reverts commit 2205d23 and relands
86dc6e1 and
7ab16fb.

Original commit was reverted because of failing libc++ tests, see #76232
for the discussion.

The errors in the tests are spurious in the first place (coming from
initialization of invalid classes), so update the tests to match new
behavior that does not show those errors.

The original patch was written by @ilya-biryukov

To fix the CI two libc++ tests are temporary disabled for clang-18.

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Revert "Reapply "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)"

This reverts commit 02347fc7191ff4d073f439dde6523add3f5496de.

These changes break the libc++

Revert "Reapply "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)"

This reverts commit 02347fc7191ff4d073f439dde6523add3f5496de.

These changes break the libc++ CI again.
I'll look at a better solution later.

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Reapply "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)

With updates the libc++ tests.

This reverts commit 2205d2334f3c859ad9f6c65ed950bfb3bb6f7cbe and relan

Reapply "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)

With updates the libc++ tests.

This reverts commit 2205d2334f3c859ad9f6c65ed950bfb3bb6f7cbe and relands
86dc6e15f22610bbb53eb4efda0a178ecefc933a and
7ab16fb5207fe187ab999f882069bd632d2e68e5.

Original commit was reverted because of failing libc++ tests, see #76232 for
the discussion.

The errors in the tests are spurious in the first place (coming from initialization
of invalid classes), so update the tests to match new behavior that does
not show those errors.

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Revert "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)

Reverts llvm/llvm-project#76232 and
7ab16fb5207fe187ab999f882069bd632d2e68e5 to recover build bots.

Revert "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)

Reverts llvm/llvm-project#76232 and
7ab16fb5207fe187ab999f882069bd632d2e68e5 to recover build bots.

Breaks libc++ tests, details in #76232

#76228

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[Sema] Update test for previous change

The warning for C++20 extension does not fire in on specific instance
because conversion now fails as class is invalid because of an invalid
member.

The new b

[Sema] Update test for previous change

The warning for C++20 extension does not fire in on specific instance
because conversion now fails as class is invalid because of an invalid
member.

The new behavior is expected, so updating the test accordingly

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Diagnose use of VLAs in C++ by default

Reapplication of 7339c0f782d5c70e0928f8991b0c05338a90c84c with a fix
for a crash involving arrays without a size expression.

Clang supports VLAs in C++ as an

Diagnose use of VLAs in C++ by default

Reapplication of 7339c0f782d5c70e0928f8991b0c05338a90c84c with a fix
for a crash involving arrays without a size expression.

Clang supports VLAs in C++ as an extension, but we currently only warn
on their use when you pass -Wvla, -Wvla-extension, or -pedantic.
However, VLAs as they're expressed in C have been considered by WG21
and rejected, are easy to use accidentally to the surprise of users
(e.g., https://ddanilov.me/default-non-standard-features/), and they
have potential security implications beyond constant-size arrays
(https://wiki.sei.cmu.edu/confluence/display/c/ARR32-C.+Ensure+size+arguments+for+variable+length+arrays+are+in+a+valid+range).
C++ users should strongly consider using other functionality such as
std::vector instead.

This seems like sufficiently compelling evidence to warn users about
VLA use by default in C++ modes. This patch enables the -Wvla-extension
diagnostic group in C++ language modes by default, and adds the warning
group to -Wall in GNU++ language modes. The warning is still opt-in in
C language modes, where support for VLAs is somewhat less surprising to
users.

RFC: https://discourse.llvm.org/t/rfc-diagnosing-use-of-vlas-in-c/73109
Fixes https://github.com/llvm/llvm-project/issues/62836
Differential Revision: https://reviews.llvm.org/D156565

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Revert "Diagnose use of VLAs in C++ by default"

This reverts commit 7339c0f782d5c70e0928f8991b0c05338a90c84c.

Breaks bots:
https://lab.llvm.org/buildbot/#/builders/139/builds/51875
https://lab.llvm

Revert "Diagnose use of VLAs in C++ by default"

This reverts commit 7339c0f782d5c70e0928f8991b0c05338a90c84c.

Breaks bots:
https://lab.llvm.org/buildbot/#/builders/139/builds/51875
https://lab.llvm.org/buildbot/#/builders/164/builds/45262

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Diagnose use of VLAs in C++ by default

Clang supports VLAs in C++ as an extension, but we currently only warn
on their use when you pass -Wvla, -Wvla-extension, or -pedantic.
However, VLAs as they'r

Diagnose use of VLAs in C++ by default

Clang supports VLAs in C++ as an extension, but we currently only warn
on their use when you pass -Wvla, -Wvla-extension, or -pedantic.
However, VLAs as they're expressed in C have been considered by WG21
and rejected, are easy to use accidentally to the surprise of users
(e.g., https://ddanilov.me/default-non-standard-features/), and they
have potential security implications beyond constant-size arrays
(https://wiki.sei.cmu.edu/confluence/display/c/ARR32-C.+Ensure+size+arguments+for+variable+length+arrays+are+in+a+valid+range).
C++ users should strongly consider using other functionality such as
std::vector instead.

This seems like sufficiently compelling evidence to warn users about
VLA use by default in C++ modes. This patch enables the -Wvla-extension
diagnostic group in C++ language modes by default, and adds the warning
group to -Wall in GNU++ language modes. The warning is still opt-in in
C language modes, where support for VLAs is somewhat less surprising to
users.

RFC: https://discourse.llvm.org/t/rfc-diagnosing-use-of-vlas-in-c/73109
Fixes https://github.com/llvm/llvm-project/issues/62836
Differential Revision: https://reviews.llvm.org/D156565

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[clang][Interp] Create only globals when initializing a global variable

For this code:

struct O {
int &&j;
};

O o1(0);

The generated AST for the initializer of o1 is:

VarDecl 0x62100006ab08 <a

[clang][Interp] Create only globals when initializing a global variable

For this code:

struct O {
int &&j;
};

O o1(0);

The generated AST for the initializer of o1 is:

VarDecl 0x62100006ab08 <array.cpp:119:3, col:9> col:5 o1 'O':'O' parenlistinit
`-ExprWithCleanups 0x62100006b250 <col:7, col:9> 'O':'O'
`-CXXParenListInitExpr 0x62100006b210 <col:7, col:9> 'O':'O'
`-MaterializeTemporaryExpr 0x62100006b1f0 <col:8> 'int' xvalue
`-IntegerLiteral 0x62100006abd0 <col:8> 'int' 0

Before this patch, we create a local temporary variable for the
MaterializeTemporaryExpr and destroy it again when destroying the
EvalEmitter we create to interpret the initializer. However, since
O::j is a reference, this reference now points to a local variable
that doesn't exist anymore.

Differential Revision: https://reviews.llvm.org/D156453

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[Clang] Fix the location of default init expressions

Default member initializations constructed from
a parenthesized aggregate initialization should be constructed
at the location of the left paren,

[Clang] Fix the location of default init expressions

Default member initializations constructed from
a parenthesized aggregate initialization should be constructed
at the location of the left paren, to be consistent with
brace initialization.
Otherwise we get diagmostics and source_location in the wrong places.

Fixes #63903

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D155573

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[clang] Fix a crash when casting to an array type

In C++20, if Clang fails to perform constructor overload on a
RecordType, then Clang will try to perform parentesized aggregate
initialization. If t

[clang] Fix a crash when casting to an array type

In C++20, if Clang fails to perform constructor overload on a
RecordType, then Clang will try to perform parentesized aggregate
initialization. If that fails and the initialization was attempted as
part of a cast, then we should get the diagnostics from the failed
constructor overload attempt. However, we don't attempt constructor
overloading for arrays, so previously, if we try to diagnose an
overloaded cast for a parenthesized aggregate initialization of an
array, we crash. To fix this, we now exit tryDiagnoseOverloadedCast(...)
for failed parentesized list initialization if the destination type is
an array.

Fixes #63758

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D155523

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[Clang] Fix a crash when trying to initialize an invalid aggregate.

We did not return an error when failing to producing
a valid expression when performing the initialization of
an aggregate initial

[Clang] Fix a crash when trying to initialize an invalid aggregate.

We did not return an error when failing to producing
a valid expression when performing the initialization of
an aggregate initialized with a parenthesized list of expressions.

This is a regression introduced in Clang 17.

Fixes #63278

Reviewed By: aaron.ballman, #clang-language-wg

Differential Revision: https://reviews.llvm.org/D154486

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[clang] Fix crash when passing a braced-init list to a parentehsized aggregate init expression

The previous code incorrectly assumed that we would never call
warnBracedScalarInit(...) with a EK_Pare

[clang] Fix crash when passing a braced-init list to a parentehsized aggregate init expression

The previous code incorrectly assumed that we would never call
warnBracedScalarInit(...) with a EK_ParenAggInitMember. This patch fixes
the bug by warning when a scalar member is initialized via a braced-init
list when performing a parentehsized aggregate initialization. This
behavior is consistent with parentehsized list aggregate initialization.

Fixes #63008

Reviewed By: shafik

Differential Revision: https://reviews.llvm.org/D151763

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[clang] Fix overly aggressive lifetime checks for parenthesized aggregate initialization

Before this patch, initialized class members would have the LifetimeKind
LK_MemInitializer, which does not al

[clang] Fix overly aggressive lifetime checks for parenthesized aggregate initialization

Before this patch, initialized class members would have the LifetimeKind
LK_MemInitializer, which does not allow for binding a temporary to a
reference. Binding to a temporary however is allowed in parenthesized
aggregate initialization, even if it leads to a dangling reference. To
fix this, we create a new EntityKind, EK_ParenAggInitMember, which has
LifetimeKind LK_FullExpression.

This patch does *not* attempt to diagnose dangling references as a
result of using this feature.

This patch also refactors TryOrBuildParenListInitialization(...) to
accomodate creating different InitializedEntity objects.

Fixes #61567

[0]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0960r3.html

Reviewed By: shafik

Differential Revision: https://reviews.llvm.org/D148274

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[clang] Fix a crash with parenthesized aggregate initialization and base classes

When calling InitializeBase(...), TryOrBuidlParenListInit(...) needs to
pass in the parent entity; otherwise, we erro

[clang] Fix a crash with parenthesized aggregate initialization and base classes

When calling InitializeBase(...), TryOrBuidlParenListInit(...) needs to
pass in the parent entity; otherwise, we erroneously try to cast
CurContext to a CXXConstructorDecl[0], which can't be done since we're
performing aggregate initialization, not constructor initialization.

Field initialization is not affected, but this patch still adds some
tests for it.

Fixes 62296

[0]: https://github.com/llvm/llvm-project/blob/33d6bd1c667456f7f4a9d338a7996a30a3af50a3/clang/lib/Sema/SemaAccess.cpp#L1696

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D149301

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[clang] Fix 2 bugs with parenthesized aggregate initialization

* Fix an issue where temporaries initialized via parenthesized aggregate
initialization don't get destroyed.
* Fix an issue where agg

[clang] Fix 2 bugs with parenthesized aggregate initialization

* Fix an issue where temporaries initialized via parenthesized aggregate
initialization don't get destroyed.
* Fix an issue where aggregate initialization omits calls to class
members' move constructors after a TreeTransform. This occurs because
the CXXConstructExpr wrapping the call to the move constructor gets
unboxed during a TreeTransform of the wrapping FunctionalCastExpr (as with a
InitListExpr), but unlike InitListExpr, we dont reperform the
InitializationSequence for the list's expressions to regenerate the
CXXConstructExpr. This patch fixes this bug by treating
CXXParenListInitExpr identically to InitListExpr in this regard.

Fixes #61145

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D146465

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[clang] Reland parenthesized aggregate init patches

This commit relands the patches for implementing P0960R3 and P1975R0,
which describe initializing aggregates via a parenthesized list.

The reland

[clang] Reland parenthesized aggregate init patches

This commit relands the patches for implementing P0960R3 and P1975R0,
which describe initializing aggregates via a parenthesized list.

The relanded commits are:

* 40c52159d3ee - P0960R3 and P1975R0: Allow initializing aggregates from
a parenthesized list of values
* c77a91bb7ba7 - Remove overly restrictive aggregate paren init logic
* 32d7aae04fdb - Fix a clang crash on invalid code in C++20 mode

This patch also fixes a crash in the original implementation.
Previously, if the input tried to call an implicitly deleted copy or
move constructor of a union, we would then try to initialize the union
by initializing it's first element with a reference to a union. This
behavior is incorrect (we should fail to initialize) and if the type of
the first element has a constructor with a single template typename
parameter, then Clang will explode. This patch fixes that issue by
checking that constructor overload resolution did not result in a
deleted function before attempting parenthesized aggregate
initialization.

Additionally, this patch also includes D140159, which contains some
minor fixes made in response to code review comments in the original
implementation that were made after that patch was submitted.

Co-authored-by: Sheng <ox59616e@gmail.com>

Fixes #54040, Fixes #59675

Reviewed By: ilya-biryukov

Differential Revision: https://reviews.llvm.org/D141546

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[clang][C++20] P0960R3 and P1975R0: Allow initializing aggregates from a parenthesized list of values

This patch implements P0960R3, which allows initialization of aggregates
via parentheses.

As an

[clang][C++20] P0960R3 and P1975R0: Allow initializing aggregates from a parenthesized list of values

This patch implements P0960R3, which allows initialization of aggregates
via parentheses.

As an example:

```
struct S { int i, j; };
S s1(1, 1);

int arr1[2](1, 2);
```

This patch also implements P1975R0, which fixes the wording of P0960R3
for single-argument parenthesized lists so that statements like the
following are allowed:

```
S s2(1);
S s3 = static_cast<S>(1);
S s4 = (S)1;

int (&&arr2)[] = static_cast<int[]>(1);
int (&&arr3)[2] = static_cast<int[2]>(1);
```

This patch was originally authored by @0x59616e and completed by
@ayzhao.

Fixes #54040, Fixes #54041

Co-authored-by: Sheng <ox59616e@gmail.com>

Full write up : https://discourse.llvm.org/t/c-20-rfc-suggestion-desired-regarding-the-implementation-of-p0960r3/63744

Reviewed By: ilya-biryukov

Differential Revision: https://reviews.llvm.org/D129531

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