r371605 - [Diagnostics] Add -Wsizeof-array-div
Nico Weber via cfe-commits
cfe-commits at lists.llvm.org
Mon Sep 23 06:07:28 PDT 2019
It still warns if the inner array is in a struct. That's probably ok though.
struct Point {
int xy[2];
};
void f() {
Point points[3];
for (int i = 0; i < sizeof(points) / sizeof(int); ++i)
(&points[0].xy[0])[i] = 0;
}
On Mon, Sep 23, 2019 at 8:54 AM Nico Weber <thakis at chromium.org> wrote:
> That was fast. Thanks much! :)
>
> On Mon, Sep 23, 2019 at 8:52 AM Dávid Bolvanský <david.bolvansky at gmail.com>
> wrote:
>
>> Hello,
>>
>> Thanks for the proposed idea, implemented in rL372600.
>>
>> po 23. 9. 2019 o 14:23 Nico Weber <thakis at chromium.org> napísal(a):
>>
>>> We're looking at turning this one.
>>>
>>> One thing that this warns about that's a false positive where we've seen
>>> it is this code for nested arrays:
>>>
>>> float m[4][4];
>>> for (int i = 0; i < sizeof(m) / sizeof(**m); ++i) (&**m)[i] = 0;
>>>
>>> (Why would anyone write code like this? It's a reduced example; consider
>>> e.g. wanting to call std::generate_n() on all elements of a nested array.)
>>>
>>> Can we make the warning not fire when dividing the size of a nested
>>> array by the size of the deepest base type?
>>>
>>> On Wed, Sep 11, 2019 at 6:58 AM David Bolvansky via cfe-commits <
>>> cfe-commits at lists.llvm.org> wrote:
>>>
>>>> Author: xbolva00
>>>> Date: Wed Sep 11 03:59:47 2019
>>>> New Revision: 371605
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=371605&view=rev
>>>> Log:
>>>> [Diagnostics] Add -Wsizeof-array-div
>>>>
>>>> Summary: Clang version of https://www.viva64.com/en/examples/v706/
>>>>
>>>> Reviewers: rsmith
>>>>
>>>> Differential Revision: https://reviews.llvm.org/D67287
>>>>
>>>> Added:
>>>> cfe/trunk/test/Sema/div-sizeof-array.cpp
>>>> Modified:
>>>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>> cfe/trunk/lib/Sema/SemaExpr.cpp
>>>>
>>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=371605&r1=371604&r2=371605&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Wed Sep 11
>>>> 03:59:47 2019
>>>> @@ -3406,6 +3406,10 @@ def note_pointer_declared_here : Note<
>>>> def warn_division_sizeof_ptr : Warning<
>>>> "'%0' will return the size of the pointer, not the array itself">,
>>>> InGroup<DiagGroup<"sizeof-pointer-div">>;
>>>> +def warn_division_sizeof_array : Warning<
>>>> + "expression does not compute the number of elements in this array;
>>>> element "
>>>> + "type is %0, not %1">,
>>>> + InGroup<DiagGroup<"sizeof-array-div">>;
>>>>
>>>> def note_function_warning_silence : Note<
>>>> "prefix with the address-of operator to silence this warning">;
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=371605&r1=371604&r2=371605&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Wed Sep 11 03:59:47 2019
>>>> @@ -9158,17 +9158,28 @@ static void DiagnoseDivisionSizeofPointe
>>>> else
>>>> RHSTy = RUE->getArgumentExpr()->IgnoreParens()->getType();
>>>>
>>>> - if (!LHSTy->isPointerType() || RHSTy->isPointerType())
>>>> - return;
>>>> - if (LHSTy->getPointeeType().getCanonicalType().getUnqualifiedType()
>>>> !=
>>>> - RHSTy.getCanonicalType().getUnqualifiedType())
>>>> - return;
>>>> + if (LHSTy->isPointerType() && !RHSTy->isPointerType()) {
>>>> + if (!S.Context.hasSameUnqualifiedType(LHSTy->getPointeeType(),
>>>> RHSTy))
>>>> + return;
>>>>
>>>> - S.Diag(Loc, diag::warn_division_sizeof_ptr) << LHS <<
>>>> LHS->getSourceRange();
>>>> - if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
>>>> - if (const ValueDecl *LHSArgDecl = DRE->getDecl())
>>>> - S.Diag(LHSArgDecl->getLocation(),
>>>> diag::note_pointer_declared_here)
>>>> - << LHSArgDecl;
>>>> + S.Diag(Loc, diag::warn_division_sizeof_ptr) << LHS <<
>>>> LHS->getSourceRange();
>>>> + if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
>>>> + if (const ValueDecl *LHSArgDecl = DRE->getDecl())
>>>> + S.Diag(LHSArgDecl->getLocation(),
>>>> diag::note_pointer_declared_here)
>>>> + << LHSArgDecl;
>>>> + }
>>>> + } else if (const auto *ArrayTy = S.Context.getAsArrayType(LHSTy)) {
>>>> + QualType ArrayElemTy = ArrayTy->getElementType();
>>>> + if (ArrayElemTy->isDependentType() || RHSTy->isDependentType() ||
>>>> + S.Context.getTypeSize(ArrayElemTy) ==
>>>> S.Context.getTypeSize(RHSTy))
>>>> + return;
>>>> + S.Diag(Loc, diag::warn_division_sizeof_array)
>>>> + << LHSArg->getSourceRange() << ArrayElemTy << RHSTy;
>>>> + if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
>>>> + if (const ValueDecl *LHSArgDecl = DRE->getDecl())
>>>> + S.Diag(LHSArgDecl->getLocation(),
>>>> diag::note_array_declared_here)
>>>> + << LHSArgDecl;
>>>> + }
>>>> }
>>>> }
>>>>
>>>>
>>>> Added: cfe/trunk/test/Sema/div-sizeof-array.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/div-sizeof-array.cpp?rev=371605&view=auto
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Sema/div-sizeof-array.cpp (added)
>>>> +++ cfe/trunk/test/Sema/div-sizeof-array.cpp Wed Sep 11 03:59:47 2019
>>>> @@ -0,0 +1,28 @@
>>>> +// RUN: %clang_cc1 %s -verify -Wsizeof-array-div -fsyntax-only
>>>> +
>>>> +template <typename Ty, int N>
>>>> +int f(Ty (&Array)[N]) {
>>>> + return sizeof(Array) / sizeof(Ty); // Should not warn
>>>> +}
>>>> +
>>>> +typedef int int32;
>>>> +
>>>> +void test(void) {
>>>> + int arr[12]; // expected-note 2 {{array 'arr'
>>>> declared here}}
>>>> + unsigned long long arr2[4];
>>>> + int *p = &arr[0];
>>>> + int a1 = sizeof(arr) / sizeof(*arr);
>>>> + int a2 = sizeof arr / sizeof p; // expected-warning {{expression
>>>> does not compute the number of elements in this array; element type is
>>>> 'int', not 'int *'}}
>>>> + int a4 = sizeof arr2 / sizeof p;
>>>> + int a5 = sizeof(arr) / sizeof(short); // expected-warning
>>>> {{expression does not compute the number of elements in this array; element
>>>> type is 'int', not 'short'}}
>>>> + int a6 = sizeof(arr) / sizeof(int32);
>>>> + int a7 = sizeof(arr) / sizeof(int);
>>>> + int a9 = sizeof(arr) / sizeof(unsigned int);
>>>> + const char arr3[2] = "A";
>>>> + int a10 = sizeof(arr3) / sizeof(char);
>>>> +
>>>> + int arr4[10][12]; // expected-note 3 {{array
>>>> 'arr4' declared here}}
>>>> + int b1 = sizeof(arr4) / sizeof(arr2[12]); // expected-warning
>>>> {{expression does not compute the number of elements in this array; element
>>>> type is 'int [12]', not 'unsigned long long'}}
>>>> + int b2 = sizeof(arr4) / sizeof(int *); // expected-warning
>>>> {{expression does not compute the number of elements in this array; element
>>>> type is 'int [12]', not 'int *'}}
>>>> + int b3 = sizeof(arr4) / sizeof(short *); // expected-warning
>>>> {{expression does not compute the number of elements in this array; element
>>>> type is 'int [12]', not 'short *'}}
>>>> +}
>>>>
>>>>
>>>> _______________________________________________
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>>>> cfe-commits at lists.llvm.org
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>>>>
>>>
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