Re: [PATCH 1/2] builtin/merge-file: fix compiler error on MacOS with clang 11.0.0

["René Scharfe" <l.s.r@web.de>]

Am 06.10.22 um 21:43 schrieb Jeff Hostetler via GitGitGadget:
> From: Jeff Hostetler <jeffhost@microsoft.com>
>
> Add extra set of braces around zero initialization of two array/structure
> variables to resolve compiler errors/warnings from clang 11.0.0 on MacOS.
> This is not needed on clang 14.0.

Not sure how the Apple version numbers map to LLVM versions.  I can
reproduce it with Godbolt's Compiler Explorer with clang 8, but not
with clang 9 or higher: https://godbolt.org/z/f7f7s9xxz

Funny that type of the "inner" member seems to affect the warning.

>
> $ uname -a
> Darwin jeffhost-mbp.local 19.6.0 Darwin Kernel Version 19.6.0: \
>        Mon Apr 18 21:50:40 PDT 2022; \
>        root:xnu-6153.141.62~1/RELEASE_X86_64 x86_64
> $ clang -v
> Apple clang version 11.0.0 (clang-1100.0.33.17)
> Target: x86_64-apple-darwin19.6.0
> [...]
>
> $ make builtin/merge-file.o
>     CC builtin/merge-file.o
> builtin/merge-file.c:29:23: error: suggest braces around initialization \
> 			    of subobject [-Werror,-Wmissing-braces]
>         mmfile_t mmfs[3] = { 0 };
>                              ^
>                              {}

{0} is an idiom to zero-initialize any struct, no matter how deeply
nested.  It's valid C and the compiler warning about it is not helpful.
Shouldn't we rather silence it with -Wno-missing-braces?

On the other hand: Uglifying just three initializations in total isn't
that bad.  The issue may reappear, though, because most people use
compilers that don't issue that spurious warning, I imagine.

> builtin/merge-file.c:31:20: error: suggest braces around initialization \
> 			    of subobject [-Werror,-Wmissing-braces]
>         xmparam_t xmp = { 0 };
>                           ^
>                           {}
> 2 errors generated.
> make: *** [builtin/merge-file.o] Error 1
>
> Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
> ---
>  builtin/merge-file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/merge-file.c b/builtin/merge-file.c
> index c923bbf2abb..607c3d3f9e1 100644
> --- a/builtin/merge-file.c
> +++ b/builtin/merge-file.c
> @@ -26,9 +26,9 @@ static int label_cb(const struct option *opt, const char *arg, int unset)
>  int cmd_merge_file(int argc, const char **argv, const char *prefix)
>  {
>  	const char *names[3] = { 0 };
> -	mmfile_t mmfs[3] = { 0 };
> +	mmfile_t mmfs[3] = { { 0 } };
>  	mmbuffer_t result = { 0 };
> -	xmparam_t xmp = { 0 };
> +	xmparam_t xmp = { { 0 } };
>  	int ret = 0, i = 0, to_stdout = 0;
>  	int quiet = 0;
>  	struct option options[] = {