r371605 - [Diagnostics] Add -Wsizeof-array-div
Nico Weber via cfe-commits
cfe-commits at lists.llvm.org
Mon Sep 23 05:54:34 PDT 2019
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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>>
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