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

[Argyrios Kyrtzidis]

On Apr 4, 2013, at 6:33 PM, Loïc Jaquemet <loic.jaquemet at gmail.com> wrote:

> ah yes.
> The lookup failure. I forgot that one instance.
> 
> Attached patches pass tests on r178827.

I think you meant to attach different files, these look like earlier versions of your patches (e.g. clang_getAlignOf, instead of clang_Type_getAlignOf)

> 
> 
> 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
> <expose-ast-record-layout-001><expose-ast-record-layout-002-tests><expose-ast-record-layout-003-python-bindings><expose-ast-record-layout-004-python-bindings-tests>

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