[clang] 2bd8493 - Improve type printing of const arrays to normalize array-of-const and const-array
David Blaikie via cfe-commits
cfe-commits at lists.llvm.org
Tue Oct 12 19:35:28 PDT 2021
On Mon, Oct 11, 2021 at 2:46 PM Richard Smith <richard at metafoo.co.uk> wrote:
> On Wed, 15 Sept 2021 at 13:52, David Blaikie <dblaikie at gmail.com> wrote:
>
>> On Tue, Sep 14, 2021 at 10:04 AM Richard Smith <richard at metafoo.co.uk>
>> wrote:
>>
>>> On Mon, 13 Sept 2021 at 19:24, David Blaikie via cfe-commits <
>>> cfe-commits at lists.llvm.org> wrote:
>>>
>>>>
>>>> Author: David Blaikie
>>>> Date: 2021-09-13T19:17:05-07:00
>>>> New Revision: 2bd84938470bf2e337801faafb8a67710f46429d
>>>>
>>>> URL:
>>>> https://github.com/llvm/llvm-project/commit/2bd84938470bf2e337801faafb8a67710f46429d
>>>> DIFF:
>>>> https://github.com/llvm/llvm-project/commit/2bd84938470bf2e337801faafb8a67710f46429d.diff
>>>>
>>>> LOG: Improve type printing of const arrays to normalize array-of-const
>>>> and const-array
>>>>
>>>> Since these map to the same effective type - render them the same/in the
>>>> more legible way (const x[n]).
>>>>
>>>
>>> Nice!
>>>
>>>
>>>> Added:
>>>>
>>>>
>>>> Modified:
>>>> clang/lib/AST/TypePrinter.cpp
>>>> clang/test/ARCMT/cxx-checking.mm
>>>> clang/test/AST/ast-dump-APValue-arithmetic.cpp
>>>> clang/test/AST/ast-dump-APValue-array.cpp
>>>> clang/test/CXX/basic/basic.types/p10.cpp
>>>> clang/test/Sema/assign.c
>>>> clang/test/Sema/typedef-retain.c
>>>> clang/test/SemaCXX/reinterpret-cast.cpp
>>>> clang/test/SemaCXX/static-assert-cxx17.cpp
>>>>
>>>> Removed:
>>>>
>>>>
>>>>
>>>>
>>>> ################################################################################
>>>> diff --git a/clang/lib/AST/TypePrinter.cpp
>>>> b/clang/lib/AST/TypePrinter.cpp
>>>> index aef1e4f3f4953..251db97c7db08 100644
>>>> --- a/clang/lib/AST/TypePrinter.cpp
>>>> +++ b/clang/lib/AST/TypePrinter.cpp
>>>> @@ -200,11 +200,12 @@ bool TypePrinter::canPrefixQualifiers(const Type
>>>> *T,
>>>> // type expands to a simple string.
>>>> bool CanPrefixQualifiers = false;
>>>> NeedARCStrongQualifier = false;
>>>> - Type::TypeClass TC = T->getTypeClass();
>>>> + const Type *UnderlyingType = T;
>>>> if (const auto *AT = dyn_cast<AutoType>(T))
>>>> - TC = AT->desugar()->getTypeClass();
>>>> + UnderlyingType = AT->desugar().getTypePtr();
>>>> if (const auto *Subst = dyn_cast<SubstTemplateTypeParmType>(T))
>>>> - TC = Subst->getReplacementType()->getTypeClass();
>>>> + UnderlyingType = Subst->getReplacementType().getTypePtr();
>>>> + Type::TypeClass TC = UnderlyingType->getTypeClass();
>>>>
>>>> switch (TC) {
>>>> case Type::Auto:
>>>> @@ -243,6 +244,9 @@ bool TypePrinter::canPrefixQualifiers(const Type *T,
>>>>
>>>> case Type::ConstantArray:
>>>> case Type::IncompleteArray:
>>>> + return canPrefixQualifiers(
>>>> +
>>>> cast<ArrayType>(UnderlyingType)->getElementType().getTypePtr(),
>>>> + NeedARCStrongQualifier);
>>>> case Type::VariableArray:
>>>> case Type::DependentSizedArray:
>>>>
>>>
>>> Can we give these two cases the same treatment?
>>>
>>
>> Handled the DependentSizedArray in
>> https://github.com/llvm/llvm-project/commit/40acc0adad59ac39e9a7a02fcd93161298500c00
>>
>> But per the comment in that commit I wasn't able to reproduce the problem
>> with a variable array - though we could include it in the handling on
>> principle/for consistency, even without a test/etc. Perhaps there's a way
>> to test/provoke the behavior you might know that I couldn't figure out?
>>
>> Details from the commit:
>>
>> The VariableArray case I couldn't figure out how to test/provoke -
>> you
>>
>> can't write/form a variable array in any context other than a local
>>
>> variable that I know of, and in that case `const int x[n]` is the
>>
>> normalized form already (array-of-const) and you can't use typedefs
>>
>> (since you can't typedef int[n] with variable 'n') to force the
>>
>> const-array AST that would produce the undesirable type printing "int
>>
>> const [n]".
>>
>
> C has a fairly surprising rule here -- you actually can define a VLA type
> in a local typedef. For example,
>
> void f(int n) {
> typedef int arr[n];
> const arr x;
> }
>
> ... is valid in C. In C++ mode, this produces:
>
> <source>:3:15: error: default initialization of an object of const type
> 'const arr' (aka 'int const[n]')
>
> (note, 'int const[n]' not 'const int[n]').
>
Oh, right, good to understand! Yep, fixed and tested with this:
39093279f2ede4af9048b89d048d7fe9182a50f8
Huh, funny diagnostic experience aside here: https://godbolt.org/z/W46b3qc49
void f(int i) {
typedef int x[i];
const x y = {};
}
<source>:2:19: error: variable-sized object may not be initialized
typedef int x[i];
^
With no pointer/note/etc to the 'y' variable - the typedef and variable
could be quite far apart. The diagnostic would be hard to read/understand.
> Oh, also - another quirk of array type printing that I'd be up for
>> addressing if you've got an opinion on it:
>>
>> "int [n]" is printed with a space between the "int" and array.
>> "int *const[n]" is printed without a space before the array (though both
>> have a space after "int")
>>
>> ClangFormat formats these as "int[n]" and "int *const[n]" - with *
>> left/right depending on ClangFormat's heuristics/configuration.
>>
>> Reckon we should remove the space in "int[n]"?
>>
>
> I think we should make it consistent, one way or the other. Beyond that,
> the decision seems somewhat arbitrary, but following clang-format seems
> reasonable to me. I certainly would expect `int *[n]` rather than `int *
> [n]`, which similarly suggests omitting the space here.
>
It looks like the cause is this:
https://github.com/llvm/llvm-project/blob/40acc0adad59ac39e9a7a02fcd93161298500c00/clang/lib/AST/TypePrinter.cpp#L508
But there seem to be a lot of similar code with NonEmptyPH that presumably
has similar effects - any idea why?
Cases include:
PointerBefore (changes 'char *' to 'char*' (though 'char *[N]' keeps the
space before the '*')
PointerAfter (ah, seems to be related to the closing ")" in "void (*const)"
- so I would've /thought/ the leading "(" would be disabled by removing the
NonEmptyPH in PointerBefore... but apparently not? So I'm not sure why the
asymmetry here - might be more related to the PrevPHIsEmpty in
printBefore(Type*, Qualifiers, raw_ostream))
BlockPointerBefore
BlockPointerAfter
LValueReferenceBefore
LValueReferenceAfter
RValueReferenceBefore
RValueReferenceAfter
MemberPointerBefore
MemberPointerAfter
ConstantArrayBefore
IncompleteArrayBefore
VariableArrayBefore
DependentSizedArrayBefore
FunctionProtoAfter
FunctionNoProtoAfter
Still playing around with some other cases here to better understand. I
guess some stuff uses NonEmptyPlaceHolder for when, for instance, the
qualifier has to go on the right ("void *const") so when printing the
underlying pointer type, it has a non-empty place holder (the const) but
the const itself has an empty placeholder (no variable name), etc.
I'll try just removing the array ones, see what that looks like.
NeedARCStrongQualifier = true;
>>>
>>>
>>>> diff --git a/clang/test/ARCMT/cxx-checking.mm b/clang/test/ARCMT/
>>>> cxx-checking.mm
>>>> index 952f3cdcbb79c..d6441def09b40 100644
>>>> --- a/clang/test/ARCMT/cxx-checking.mm
>>>> +++ b/clang/test/ARCMT/cxx-checking.mm
>>>> @@ -80,7 +80,7 @@
>>>>
>>>> struct FlexibleArrayMember0 {
>>>> int length;
>>>> - id array[]; // expected-error{{flexible array member 'array' of type
>>>> 'id __strong[]' with non-trivial destruction}}
>>>> + id array[]; // expected-error{{flexible array member 'array' of type
>>>> '__strong id []' with non-trivial destruction}}
>>>> };
>>>>
>>>> struct FlexibleArrayMember1 {
>>>>
>>>> diff --git a/clang/test/AST/ast-dump-APValue-arithmetic.cpp
>>>> b/clang/test/AST/ast-dump-APValue-arithmetic.cpp
>>>> index 835d8c8108346..e51c1cee04cfe 100644
>>>> --- a/clang/test/AST/ast-dump-APValue-arithmetic.cpp
>>>> +++ b/clang/test/AST/ast-dump-APValue-arithmetic.cpp
>>>> @@ -36,13 +36,13 @@ void Test() {
>>>> // CHECK-NEXT: | |-value: ComplexFloat 3.141500e+00 +
>>>> 4.200000e+01i
>>>>
>>>> constexpr _Complex int ArrayOfComplexInt[10] = {ComplexInt,
>>>> ComplexInt, ComplexInt, ComplexInt};
>>>> - // CHECK: | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> ArrayOfComplexInt '_Complex int const[10]' constexpr cinit
>>>> + // CHECK: | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> ArrayOfComplexInt 'const _Complex int [10]' constexpr cinit
>>>> // CHECK-NEXT: | |-value: Array size=10
>>>> // CHECK-NEXT: | | |-elements: ComplexInt 42 + 24i, ComplexInt 42
>>>> + 24i, ComplexInt 42 + 24i, ComplexInt 42 + 24i
>>>> // CHECK-NEXT: | | `-filler: 6 x ComplexInt 0 + 0i
>>>>
>>>> constexpr _Complex float ArrayOfComplexFloat[10] = {ComplexFloat,
>>>> ComplexFloat, ComplexInt, ComplexInt};
>>>> - // CHECK: `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> ArrayOfComplexFloat '_Complex float const[10]' constexpr cinit
>>>> + // CHECK: `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> ArrayOfComplexFloat 'const _Complex float [10]' constexpr cinit
>>>> // CHECK-NEXT: |-value: Array size=10
>>>> // CHECK-NEXT: | |-elements: ComplexFloat 3.141500e+00 +
>>>> 4.200000e+01i, ComplexFloat 3.141500e+00 + 4.200000e+01i, ComplexFloat
>>>> 4.200000e+01 + 2.400000e+01i, ComplexFloat 4.200000e+01 + 2.400000e+01i
>>>> // CHECK-NEXT: | `-filler: 6 x ComplexFloat 0.000000e+00 +
>>>> 0.000000e+00i
>>>>
>>>> diff --git a/clang/test/AST/ast-dump-APValue-array.cpp
>>>> b/clang/test/AST/ast-dump-APValue-array.cpp
>>>> index f9b38ec332a5b..72e519208ac56 100644
>>>> --- a/clang/test/AST/ast-dump-APValue-array.cpp
>>>> +++ b/clang/test/AST/ast-dump-APValue-array.cpp
>>>> @@ -43,7 +43,7 @@ void Test() {
>>>> constexpr float arr_f[3][5] = {
>>>> {1, 2, 3, 4, 5},
>>>> };
>>>> - // CHECK: | `-VarDecl {{.*}} <line:{{.*}}, line:{{.*}}> line:{{.*}}
>>>> arr_f 'float const[3][5]' constexpr cinit
>>>> + // CHECK: | `-VarDecl {{.*}} <line:{{.*}}, line:{{.*}}> line:{{.*}}
>>>> arr_f 'const float [3][5]' constexpr cinit
>>>> // CHECK-NEXT: | |-value: Array size=3
>>>> // CHECK-NEXT: | | |-element: Array size=5
>>>> // CHECK-NEXT: | | | |-elements: Float 1.000000e+00, Float
>>>> 2.000000e+00, Float 3.000000e+00, Float 4.000000e+00
>>>> @@ -52,7 +52,7 @@ void Test() {
>>>> // CHECK-NEXT: | | `-filler: 5 x Float 0.000000e+00
>>>>
>>>> constexpr S0 arr_s0[2] = {{1, 2}, {3, 4}};
>>>> - // CHECK: | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> arr_s0 'S0 const[2]' constexpr cinit
>>>> + // CHECK: | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> arr_s0 'const S0 [2]' constexpr cinit
>>>> // CHECK-NEXT: | |-value: Array size=2
>>>> // CHECK-NEXT: | | |-element: Struct
>>>> // CHECK-NEXT: | | | `-field: Array size=2
>>>> @@ -62,12 +62,12 @@ void Test() {
>>>> // CHECK-NEXT: | | `-elements: Int 3, Int 4
>>>>
>>>> constexpr U0 arr_u0[2] = {{.i = 42}, {.f = 3.1415f}};
>>>> - // CHECK: | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> arr_u0 'U0 const[2]' constexpr cinit
>>>> + // CHECK: | `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> arr_u0 'const U0 [2]' constexpr cinit
>>>> // CHECK-NEXT: | |-value: Array size=2
>>>> // CHECK-NEXT: | | `-elements: Union .i Int 42, Union .f Float
>>>> 3.141500e+00
>>>>
>>>> constexpr S1 arr_s1[2] = {};
>>>> - // CHECK: `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> arr_s1 'S1 const[2]' constexpr cinit
>>>> + // CHECK: `-VarDecl {{.*}} <col:{{.*}}, col:{{.*}}> col:{{.*}}
>>>> arr_s1 'const S1 [2]' constexpr cinit
>>>> // CHECK-NEXT: |-value: Array size=2
>>>> // CHECK-NEXT: | |-element: Struct
>>>> // CHECK-NEXT: | | |-field: Struct
>>>>
>>>> diff --git a/clang/test/CXX/basic/basic.types/p10.cpp
>>>> b/clang/test/CXX/basic/basic.types/p10.cpp
>>>> index aac07c76bed2e..eae0c6513ac24 100644
>>>> --- a/clang/test/CXX/basic/basic.types/p10.cpp
>>>> +++ b/clang/test/CXX/basic/basic.types/p10.cpp
>>>> @@ -32,7 +32,7 @@ struct Incomplete; // expected-note 2{{forward
>>>> declaration of 'Incomplete'}}
>>>> template<class T> struct ClassTemp {};
>>>>
>>>> constexpr Incomplete incomplete = {}; // expected-error {{constexpr
>>>> variable cannot have non-literal type 'const Incomplete'}} expected-note
>>>> {{incomplete type 'const Incomplete' is not a literal type}}
>>>> -constexpr Incomplete incomplete2[] = {}; // expected-error {{constexpr
>>>> variable cannot have non-literal type 'Incomplete const[]'}} expected-note
>>>> {{incomplete type 'Incomplete const[]' is not a literal type}}
>>>> +constexpr Incomplete incomplete2[] = {}; // expected-error {{constexpr
>>>> variable cannot have non-literal type 'const Incomplete []'}} expected-note
>>>> {{incomplete type 'const Incomplete []' is not a literal type}}
>>>> constexpr ClassTemp<int> classtemplate = {};
>>>> constexpr ClassTemp<int> classtemplate2[] = {};
>>>>
>>>>
>>>> diff --git a/clang/test/Sema/assign.c b/clang/test/Sema/assign.c
>>>> index 3edd5d4feaf2e..d65f9bf26547e 100644
>>>> --- a/clang/test/Sema/assign.c
>>>> +++ b/clang/test/Sema/assign.c
>>>> @@ -13,7 +13,7 @@ typedef int arr[10];
>>>> void test3() {
>>>> const arr b; // expected-note {{variable 'b' declared const
>>>> here}}
>>>> const int b2[10]; // expected-note {{variable 'b2' declared const
>>>> here}}
>>>> - b[4] = 1; // expected-error {{cannot assign to variable 'b'
>>>> with const-qualified type 'const arr' (aka 'int const[10]')}}
>>>> + b[4] = 1; // expected-error {{cannot assign to variable 'b'
>>>> with const-qualified type 'const arr' (aka 'const int [10]')}}
>>>> b2[4] = 1; // expected-error {{cannot assign to variable 'b2'
>>>> with const-qualified type 'const int [10]'}}
>>>> }
>>>>
>>>>
>>>> diff --git a/clang/test/Sema/typedef-retain.c
>>>> b/clang/test/Sema/typedef-retain.c
>>>> index 70e2abc1da5b8..d4358bce5ee5b 100644
>>>> --- a/clang/test/Sema/typedef-retain.c
>>>> +++ b/clang/test/Sema/typedef-retain.c
>>>> @@ -17,7 +17,7 @@ typedef int a[5];
>>>> void test3() {
>>>> typedef const a b;
>>>> b r; // expected-note {{variable 'r' declared const here}}
>>>> - r[0] = 10; // expected-error {{cannot assign to variable 'r' with
>>>> const-qualified type 'b' (aka 'int const[5]')}}
>>>> + r[0] = 10; // expected-error {{cannot assign to variable 'r' with
>>>> const-qualified type 'b' (aka 'const int [5]')}}
>>>> }
>>>>
>>>> int test4(const a y) {
>>>>
>>>> diff --git a/clang/test/SemaCXX/reinterpret-cast.cpp
>>>> b/clang/test/SemaCXX/reinterpret-cast.cpp
>>>> index 6a4bc91665448..f427af1efbafc 100644
>>>> --- a/clang/test/SemaCXX/reinterpret-cast.cpp
>>>> +++ b/clang/test/SemaCXX/reinterpret-cast.cpp
>>>> @@ -132,7 +132,7 @@ void const_arrays() {
>>>> const STRING *s;
>>>> const char *c;
>>>>
>>>> - (void)reinterpret_cast<char *>(s); // expected-error
>>>> {{reinterpret_cast from 'const STRING *' (aka 'char const (*)[10]') to
>>>> 'char *' casts away qualifiers}}
>>>> + (void)reinterpret_cast<char *>(s); // expected-error
>>>> {{reinterpret_cast from 'const STRING *' (aka 'const char (*)[10]') to
>>>> 'char *' casts away qualifiers}}
>>>> (void)reinterpret_cast<const STRING *>(c);
>>>> }
>>>>
>>>>
>>>> diff --git a/clang/test/SemaCXX/static-assert-cxx17.cpp
>>>> b/clang/test/SemaCXX/static-assert-cxx17.cpp
>>>> index fe02f8f29965f..d5601839bdd3e 100644
>>>> --- a/clang/test/SemaCXX/static-assert-cxx17.cpp
>>>> +++ b/clang/test/SemaCXX/static-assert-cxx17.cpp
>>>> @@ -94,7 +94,7 @@ void foo6() {
>>>> static_assert(static_cast<const X<typename T::T> *>(nullptr));
>>>> // expected-error at -1{{static_assert failed due to requirement
>>>> 'static_cast<const X<int> *>(nullptr)'}}
>>>> static_assert((const X<typename T::T>[]){} == nullptr);
>>>> - // expected-error at -1{{static_assert failed due to requirement
>>>> '(X<int> const[0]){} == nullptr'}}
>>>> + // expected-error at -1{{static_assert failed due to requirement
>>>> '(const X<int> [0]){} == nullptr'}}
>>>> static_assert(sizeof(X<decltype(X<typename T::T>().X<typename
>>>> T::T>::~X())>) == 0);
>>>> // expected-error at -1{{static_assert failed due to requirement
>>>> 'sizeof(X<void>) == 0'}}
>>>> static_assert(constexpr_return_false<typename T::T, typename
>>>> T::U>());
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> cfe-commits mailing list
>>>> cfe-commits at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>>
>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20211012/fe633ab5/attachment-0001.html>
More information about the cfe-commits
mailing list