r371605 - [Diagnostics] Add -Wsizeof-array-div
Dávid Bolvanský via cfe-commits
cfe-commits at lists.llvm.org
Mon Sep 23 05:52:41 PDT 2019
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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