On Mon, Mar 31, 2025 at 02:27:06PM +0200, Patrick Steinhardt wrote:
> One thing I stumbled over: the `--min-batch-size` parameter is parsed
> using `OPT_INTEGER()`, which expects the value pointer to point to an
> integer. But we pass `struct backfill_context::min_batch_size`, which is
> of type `size_t`. Maybe that's causing us to end up with an invalid
> value?
We could teach parse-options to verify at compile time that it got a
'value' pointer to an appropriately sized variable with a simple
trick:
diff --git a/parse-options.h b/parse-options.h
index 997ffbee80..ac63f9548a 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -213,7 +213,7 @@ struct option {
.type = OPTION_INTEGER, \
.short_name = (s), \
.long_name = (l), \
- .value = (v), \
+ .value = (v) + 0/(sizeof(*(v)) == sizeof(int)), \
.argh = N_("n"), \
.help = (h), \
.flags = (f), \
This bug would then cause a compiler error like this:
CC builtin/backfill.o
In file included from builtin/backfill.c:7:
builtin/backfill.c: In function ‘cmd_backfill’:
./parse-options.h:216:25: error: division by zero [-Werror=div-by-zero]
216 | .value = (v) + 0/(sizeof(*v) == sizeof(int)), \
| ^
./parse-options.h:272:37: note: in expansion of macro ‘OPT_INTEGER_F’
272 | #define OPT_INTEGER(s, l, v, h) OPT_INTEGER_F(s, l, v, h, 0)
| ^~~~~~~~~~~~~
builtin/backfill.c:126:17: note: in expansion of macro ‘OPT_INTEGER’
126 | OPT_INTEGER(0, "min-batch-size", &ctx.min_batch_size,
| ^~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [Makefile:2811: builtin/backfill.o] Error 1
Alas, the change is ugly (and we should do the same for many other
OPT_* macros as well) and the error message is far from
to-the-point... Turning this into something usable would require a
more clever trick, and that's more than I can devote to this issue.
