Re: [PATCH 3/5] reftable/stack: fix compiler warning due to missing braces

From: Carlo Arenas <carenas@gmail.com>
Date: Aug 12, 2025, 04:18 UTC
Message-ID: <qruwf2zjl2uvf33mp4ajklvgx7wq7ctghu53rxzbgndfojudvh@ylr4otznu2og>
In-Reply-To: <aJGNaQwnd6_A0Ppw@pks.im>

On Tue, Aug 05, 2025 at 06:49:45AM -0800, Patrick Steinhardt wrote:

Show 25 quoted lines

> On Mon, Aug 04, 2025 at 12:14:22PM -0700, Junio C Hamano wrote:
> > Patrick Steinhardt <ps@pks.im> writes:
> > 
> > > Yeah, in general I'm also of the opinion that we shouldn't bother. But
> > > in libgit2 we have pipelines that use such older compilers, and we don't
> > > want to drop those for now. So I think we should treat the reftable
> > > library specially, doubly so as this is the only instance that causes
> > > problems.
> > 
> > Hmph.  Shouldn't there be some kind of "shim" layer where these
> > things are defined per project convention and/or toolchain being
> > used?  So when building for git proper, you'd use {0} just as
> > everybody else do, but for others your include file supplied by that
> > project would use something else (like {{0}} in this case)?  That
> > kind of approach would be a better solution than open coding QSORT()
> > in the longer term, for example.
> 
> We do have a shim layer, but I don't think it makes sense to use it for
> every small piece. The intent of that layer is to paper over platform
> differences that we cannot easily hide away in a generic fashion. So
> things like mmap, random numbers, handling includes or registering
> lockfiles via atexit(3p).
> 
> But I don't think it makes sense to use the shim layer for things like
> `{0}` vs `{{0}}`

I think the suggestion for using a shim layer solution is relevant, because additionally to the compatibility issues of the zero initializer, you also need to take into consideration that the proposed solution will still trigger warnings when compiled as C++ (where {0} should be instead {}).

Why not do instead something like?

diff --git a/reftable/stack.c b/reftable/stack.c
index 4caf96aa1d..80ce8a7083 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -704,8 +704,6 @@ struct reftable_addition {
 	uint64_t next_update_index;
 };
 
-#define REFTABLE_ADDITION_INIT {0}
-
 static int reftable_stack_init_addition(struct reftable_addition *add,
 					struct reftable_stack *st,
 					unsigned int flags)
@@ -859,7 +857,7 @@ int reftable_stack_new_addition(struct reftable_addition **dest,
 				unsigned int flags)
 {
 	int err = 0;
-	struct reftable_addition empty = REFTABLE_ADDITION_INIT;
+	static const struct reftable_addition empty;
 
 	REFTABLE_CALLOC_ARRAY(*dest, 1);
 	if (!*dest)
@@ -879,8 +877,11 @@ static int stack_try_add(struct reftable_stack *st,
 					    void *arg),
 			 void *arg)
 {
-	struct reftable_addition add = REFTABLE_ADDITION_INIT;
-	int err = reftable_stack_init_addition(&add, st, 0);
+	struct reftable_addition add;
+	int err;
+
+	memset(&add, 0, sizeof(add));
+	err = reftable_stack_init_addition(&add, st, 0);
 	if (err < 0)
 		goto done;
 
Carlo