Re: [PATCH] revision: mark blobs needed for resolve-undo as reachable
- From
Jeff King <peff@peff.net>
- Date
- Jun 15, 2022, 03:48 UTC
- Message-ID
- <YqlWhKDFX3KESY0h@coredump.intra.peff.net>
- In-Reply-To
- <Yqk9uMS5kxHD6o7l@nand.local>
On Tue, Jun 14, 2022 at 10:02:32PM -0400, Taylor Blau wrote:
Show 22 quoted lines
> --- >8 --- > > diff --git a/string-list.h b/string-list.h > index d5a744e143..425abc55f4 100644 > --- a/string-list.h > +++ b/string-list.h > @@ -143,7 +143,7 @@ int for_each_string_list(struct string_list *list, > > /** Iterate over each item, as a macro. */ > #define for_each_string_list_item(item,list) \ > - for (item = (list)->items; \ > + for (item = (list) ? (list)->items : NULL; \ > item && item < (list)->items + (list)->nr; \ > ++item) > > --- 8< --- > > > but even with your suggestion, I get this compiler error: > > ...so did I. Though I'm not sure I understand the compiler's warning > here. Surely the thing being passed as list in the macro expansion > _won't_ always evaluate to non-NULL, will it?
In the general case, no, but in this specific expansion of the macro, it is passing the address of a local variable (&cpath), which will never be NULL. The compiler is overeager here; the check is indeed pointless in this expansion, but warning on useless macro-expanded code isn't helpful, since other macro users need it.
Hiding it in a function seems to work, even with -O2 inlining, like:
diff --git a/string-list.h b/string-list.h index d5a744e143..b28b135e11 100644 --- a/string-list.h +++ b/string-list.h @@ -141,9 +141,14 @@ void string_list_clear_func(struct string_list *list, string_list_clear_func_t c int for_each_string_list(struct string_list *list, string_list_each_func_t func, void *cb_data); +static inline struct string_list_item *string_list_first_item(const struct string_list *list) +{ + return list ? list->items : NULL; +} + /** Iterate over each item, as a macro. */ #define for_each_string_list_item(item,list) \ - for (item = (list)->items; \ + for (item = string_list_first_item(list); \ item && item < (list)->items + (list)->nr; \ ++item) -Peff