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Wed, 1 Apr 2026 08:14:08 -0400 (EDT) Received: by mail (OpenSMTPD) with ESMTPSA id b80af6a1 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Wed, 1 Apr 2026 12:14:08 +0000 (UTC) Date: Wed, 1 Apr 2026 14:14:05 +0200 From: Patrick Steinhardt To: Junio C Hamano Cc: git@vger.kernel.org Subject: Re: [PATCH 6/6] reftable: introduce "reftable-system.h" header Message-ID: References: <20260331-pks-reftable-portability-fixes-v1-0-46bfae55c68c@pks.im> <20260331-pks-reftable-portability-fixes-v1-6-46bfae55c68c@pks.im> Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Mar 31, 2026 at 11:26:35AM -0700, Junio C Hamano wrote: > Patrick Steinhardt writes: > > > We're including a couple of standard headers like in a bunch > > of locations, which makes it hard for a project to plug in their own > > logic for making required functionality available. For us this is for > > example via "compat/posix.h", which already includes all of the system > > headers relevant to us. > > Hmmm. This is interesting. > > > diff --git a/reftable/reftable-system.h b/reftable/reftable-system.h > > new file mode 100644 > > index 0000000000..f90c415182 > > --- /dev/null > > +++ b/reftable/reftable-system.h > > @@ -0,0 +1,7 @@ > > +#ifndef REFTABLE_SYSTEM_H > > +#define REFTABLE_SYSTEM_H > > + > > +#define MINGW_DONT_HANDLE_IN_USE_ERROR > > +#include "compat/posix.h" > > + > > +#endif > > This one is clearly tailored to be used in the context of our > system. > > > diff --git a/reftable/system.h b/reftable/system.h > > index dffc717bd4..52f964c04b 100644 > > --- a/reftable/system.h > > +++ b/reftable/system.h > > @@ -11,8 +11,7 @@ > > > > /* This header glues the reftable library to the rest of Git */ > > > > -#define MINGW_DONT_HANDLE_IN_USE_ERROR > > -#include "compat/posix.h" > > +#include "reftable-system.h" > > #include "compat/zlib-compat.h" > > > > #define REFTABLE_INLINE(type) static inline type > > And so far in this series, I was getting the impression that > reftable/system.c and reftable/system.h are where the target system > specific definitions are stored. > > The implementation detail of how we obtain the wallclock time at > millisecond resolution is in reftable/system.c, the implementation > detail of how our mmap() emulation can work to build reftable_mmap() > is in reftable/system.c, for example. > > But the corresponding reftable/system.h does not seem to be specific > to the target system at all---it describes the common abstraction, > like "reftable code proper is expected call reftable_mmap() on any > system" and "the way for reftable code is expected to read the > wallclock is by calling reftable_time_ms()". It almost isn't. There are a few small parts in here that are specific. I was also wondering whether I want to try and adapt it so that it can always remain the exact same. > So , just like , is expected > to have a target platform specific "implementation", and not like > that is expected to be platform neutral (this > neutrality comes from the fact that will > implement the interface specified in for the > target platform). > > Which somehow feels confusing. > > Besides, the definition of "REFTABLE_INLINE(type)" being "static > inline type", according to the explanation in [1/6], is valid only > in the context of this project, so shouldn't it be done inside > , not "? For that matter, > what about inclusion of "compat/zlib-compat.h"? Is it widely > applicable across target platforms, or very specific to our codebase > where this library is used/embedded in? It overall is a tiny bit confusing, agreed. The reftable interfaces are split into two parts: - "reftable/foo.h" contains the library-internal API surface. - "reftable/reftable-foo.h" contains the external API surface as it should be consumed by the project that embeds the reftable library. Now for most of the part, headers in the "reftable/reftable-*.h" namespace are self-contained. But naturally, we also use some types there that require us to include headers, like `uint32_t` et al. The requirements that we have here are significantly smaller though than what we expose via "reftable/system.h". So ultimately, the idea was to have "reftable/reftable-system.h" expose the POSIX-like environment that is project-specific to make the other public headers compile as standalone units. And then have the implementeation sit in "reftable/system.c". But I agree that "reftable/system.h" itself still sits somewhere in between of being platform specific and containing project-specific stuff, which isn't great. I'm overall not a 100% happy myself with the split and agree that it's somewhat confusing. An alternative would be to say that it's the caller's responsibility to ensure that our public-facing headers have all dependencies satisfied, which I think is in practice only . I'm very open to alternative suggestions though. Thanks! Patrick