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From: Iain Sandoe <idsandoe@googlemail.com>
To: Ben Boeckel <ben.boeckel@kitware.com>
Cc: Boris Kolpackov <boris@codesynthesis.com>, gcc@gcc.gnu.org
Subject: Re: [modules] Preprocessing requires compiled header unit modules
Date: Thu, 21 Apr 2022 18:59:56 +0100	[thread overview]
Message-ID: <ABB90190-BA3E-40DD-9319-0970CBCE28CF@googlemail.com> (raw)
In-Reply-To: <YmFIjb/GwaEX9GVQ@farprobe>

Hi Ben,

> On 21 Apr 2022, at 13:05, Ben Boeckel via Gcc <gcc@gcc.gnu.org> wrote:
> 
> On Thu, Apr 21, 2022 at 06:05:52 +0200, Boris Kolpackov wrote:
>> I don't think it is. A header unit (unlike a named module) may export
>> macros which could affect further dependencies. Consider:
>> 
>> import "header-unit.hpp"; // May or may not export macro FOO.

1.  If you know how this was built, then you could do an -E -fdirectives-only build (both
   GCC and clang support this now) to obtain the macros.

2.  I suppose we could invent a tool (or FE mode) to dump the macros exported by a HU ***

>> #ifdef FOO
>> import "header-unit2.hpp"
>> #endif
> 
> I agree that the header needs to be *found*, but scanning cannot require
> a pre-existing BMI for that header. A new mode likely needs to be laid
> down to get the information necessary (instead of just piggy-backing on
> `-E` behavior to get what I want).

perhaps that means (2)?

Iain

*** it’s kinda frustrating that this is hard infomation to get as a developer, so
    perhaps we can anticipate users wanting such output.


  reply	other threads:[~2022-04-21 17:59 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-24 23:46 Ben Boeckel
2022-04-21  4:05 ` Boris Kolpackov
2022-04-21 12:05   ` Ben Boeckel
2022-04-21 17:59     ` Iain Sandoe [this message]
2022-04-21 18:08       ` Ben Boeckel
2022-04-21 18:18         ` Iain Sandoe
2022-04-22 14:08     ` Boris Kolpackov
2022-04-22 15:06       ` Iain Sandoe
2022-04-25  9:20         ` Boris Kolpackov
2022-04-22 16:05       ` Ben Boeckel
2022-04-25  9:42         ` Boris Kolpackov
2022-04-25 11:34           ` Ben Boeckel

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