Modifying Anonymous Structs and Unions in Clang's AST - clang

Question

I'm attempting to write an external Clang AST modifier that translates anonymous struct and union definitions to a different form. For example, I have:
typedef struct test_case_t {
struct {
int value;
} first[1];
int second;
int third[1];
} test_case_t;
I would like to transform this to:
struct test_case_t {
struct first{
int value;
};
struct first first[1];
int second;
int third[1];
};
typedef struct test_case_t test_case_t;
However, the transform seems to drop the struct first declaration, so this is what I get instead:
struct test_case_t {
struct{ // this should be "struct first"
int value;
};
struct first first[1];
int second;
int third[1];
};
typedef struct test_case_t test_case_t;
How do I go about modifying the struct definition in place and add the first declaration name? I have the RecordDecl of the first variable definition, but I can't seem to figure out how to transform the struct definition.

Answer 1

Ultimately, this is a rather interesting idiosyncrasy of Clang's AST. When representing nested sets of structs and unions, the nested declarations and definitions are split into unique FieldDecls. The struct declaration is lexically parsed first then the variable definition is parsed. This requires that you save off a reference to the struct/union declaration and match it downstream to subsequent variable definitions. This process can be rather tricky, but mimics the following. Specifically, we're looking for struct declarations that match are not isFreeStanding()
for(RecordDecl::decl_iterator iter = RD->decls_begin(), end =
RD->decls_end(); iter != end; ++iter) {
Decl *StructDecl = nullptr;
if(FieldDecl *FD = dyn_cast_or_null<FieldDecl>(*iter)) {
// create new FD
if(const ElaboratedType * NET =
dyn_cast<ElaboratedType>(SemaRef.Context.getBaseElementType(NewFD->getType())))
{
if( StructDecl ){
RecordDecl *MyDecl = dyn_cast<RecordDecl>(StructDecl);
if( MyDecl )
MyDecl->setDeclName(FD->getDeclName());
}
}
}
}else if(TagDecl *TD = dyn_cast<TagDecl>(*iter)){
if(TD->isThisDeclarationADefinition() && !TD->isFreeStanding()){
// save StructDecl
}
}
}