[PATCH] [libclang] getSizeOf/getAlignOf/getOffsetOf (was [PATCH] Expose AST Record layout attributes to libclang)

[Loïc Jaquemet]

ah yes.
The lookup failure. I forgot that one instance.

Attached patches pass tests on r178827.


2013/4/4 Argyrios Kyrtzidis <akyrtzi at gmail.com>

>
> On Apr 4, 2013, at 12:04 AM, Loïc Jaquemet <loic.jaquemet at gmail.com>
> wrote:
>
>
>
>
> 2013/4/1 Argyrios Kyrtzidis <akyrtzi at gmail.com>
>
>>
>> +  /**
>> +   * \brief One field in the record is an incomplete Type.
>> +   */
>> +  CXTypeLayoutError_IncompleteFieldParent = -6,
>> +  /**
>> +   * \brief One field in the record is a dependent Type.
>> +   */
>> +  CXTypeLayoutError_DependentFieldParent = -7
>> +};
>>
>> This was a bit confusing until I read
>>
>> + * If in the record there is another field's type declaration that is
>> + *   an incomplete type, CXTypeLayoutError_IncompleteFieldParent is
>> returned.
>> + * If in the record there is another field's type declaration that is
>> + *   a dependent type, CXTypeLayoutError_DependentFieldParent is
>> returned.
>> + */
>>
>> Could we change it to a simpler, "the parent record is
>> incomplete/dependent" ?
>>
>>
> Given the radical code change, these confusing errors do not exists any
> more.
>
>
>
>>
>> +/**
>> + * \brief Returns 1 if the cursor specifies a Record member that is a
>> bitfield.
>> + */
>> +CINDEX_LINKAGE unsigned clang_Cursor_isBitField(CXCursor C);
>>
>> the convention that we use is "Returns non-zero if ..."
>>
>>
> done
>
>
>
>>
>> +static long long visitRecordForNamedField(const RecordDecl *RD,
>> +                                          StringRef FieldName) {
>> +  for (RecordDecl::field_iterator I = RD->field_begin(), E =
>> RD->field_end();
>> +       I != E; ++I) {
>>
> [..]
>
>> +  return visitRecordForNamedField(RD, FieldName);
>> +}
>>
>> I think there is a simpler and more efficient way to handle fields in
>> anonymous records, something like this:
>> Inside clang_Type_getOffsetOf():
>>
>>   CXTranslationUnit TU =
>>       static_cast<CXTranslationUnit>(const_cast<void*>(PT.data[1]));
>>   ASTContext &Ctx = cxtu::getASTUnit(TU)->getASTContext();
>>   IdentifierInfo *II = &Ctx.Idents.get(S);
>>   DeclarationName FieldName(II);
>>   RecordDecl::lookup_const_result Res = RD->lookup(FieldName);
>>   if (Res.size() != 1)
>>     return CXTypeLayoutError_InvalidFieldName;
>>   if (const FieldDecl *FD = dyn_cast<FieldDecl>(Res.front()))
>>     return getOffsetOfFieldDecl(FD);
>>   if (const IndirectFieldDecl *IFD =
>> dyn_cast<IndirectFieldDecl>(Res.front()))
>>     return Ctx.getFieldOffset(IFD); // Change getOffsetOfFieldDecl() to
>> accept IFD.
>>
>>   return CXTypeLayoutError_InvalidFieldName;
>>
>>
> Thanks! That was exactly was I was looking for.
>
>
> In the process of implementing that new code, I stumble on some new crash
> tests cases.
> The RecordLayoutBuilder forces me to do a full validation of all records
> fields in a record.
> I have implemented a recursive validation function to do that.
> At the end, it does simplify the testing quite a lot.
> I do have to forget about the two previously confusing error types, as
> they would not be distinguishable.
>
> So, basically, this code is now simpler and more robust.
> I added some tests cases in the Incomplete namespace to demonstrate the
> several issues I uncovered.
>
>
>
>>
>>
>> I also removed the duplicate clang_Cursor_getOffsetOf().
>> After consideration, it did not make sense, especially in the
>> anonymous record situation.
>>
>>
>> Not sure about this, clang_Cursor_getOffsetOf is arguable more useful
>> than clang_Type_getOffsetOf.
>> Let's say you have this use-case: "visit all fields in a record and get
>> their offsets". To do this (as your changes in c-index-test show) you need
>> to use this roundabout way where, you have the field, then you get its
>> name, and pass it to clang_Type_getOffsetOf which looks for the same field.
>> Can't clang_Cursor_getOffsetOf just work, for example if you have a
>> cursor for "foo" in
>>
>> struct S {
>>    struct {
>>       int foo;
>>    };
>> };
>>
>> it should just return the offset of "foo" inside "struct S".
>>
>
> That was also my feeling at the beginning.
> But after several iteration on my own code, I see that my own use of this
> function is always in a context were I do have the record's type and the
> field's name at hand.
> On top of that, the C++ standard calls for a Type signature.
> So I will keep it to that.
>
>
> Please see attached diffs.
>
>
> test/Index/print-type-size.cpp failed when I applied the diffs on top of
> r178800, could you take a look ?
>
>
> * Implementation of sizeof, alignof and offsetof for libclang.
> * Unit Tests
> * Python bindings
> * Python tests
>
> --
> Loïc Jaquemet
> <sizeof-alignof-offsetof-001><sizeof-alignof-offsetof-002-tests>
> <sizeof-alignof-offsetof-003-python-bindings>
> <sizeof-alignof-offsetof-004-python-bindings-tests>
>
>
>


-- 
Loïc Jaquemet
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