[llvm-dev] [DebugInfo][DIBuilder] Good way to pass arguments to createClassType/createMemberType

via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 7 08:43:07 PST 2019

Commentary in CGDebugInfo::CreateTypeDefinition says it first creates a forward declaration for the record, then adds the members to it using the forward declaration as the scope; then it does some sort of fixup. It looks like the fixup part is MDNode::replaceWithPermanent which is admittedly not a particularly smooth interface.
Adrian or David might be able to comment on that part.

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Adrian Prantl via llvm-dev
Sent: Wednesday, February 06, 2019 1:26 PM
To: David Blaikie
Cc: Vivien Millet; llvm-dev
Subject: Re: [llvm-dev] [DebugInfo][DIBuilder] Good way to pass arguments to createClassType/createMemberType

At least for generating DWARF the scope of of a composite type member should be irrelevant since it will always be nested inside its parent.

-- adrian

On Feb 6, 2019, at 10:24 AM, David Blaikie <dblaikie at gmail.com<mailto:dblaikie at gmail.com>> wrote:

A good rough rule of thumb here is "what would/does Clang do?" & it looks (to me, on a very cursory glance) like Clang mostly passes the unit's DIFile as the scope parameter for a member - so perhaps it's just ignored? not sure.
On Tue, Feb 5, 2019 at 1:38 PM Vivien Millet via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
I'm trying to use DIBuilder to build my debug info and export it into a PDB, but I don't understand the way some DIBuilder method work.
My question might have a straightforward answer but I don't see it ... (and I can't find any example code using these methods anywhere).
Indeed createClassType takes an "Elements" argument, and createMemberType takes a "Scope" argument. Like the "who's first, egg or hen", I don't know If I need to create my members first using le compilation unit as the scope, put them in an array and give them to createClassType Elements parameter. Or forget the Elements parameter, call createClassType first then give it as "Scope" of createMemberType..
Thanks !
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