Re: [PATCH] revision: mark blobs needed for resolve-undo as reachable
From: Jeff King <hidden>
Date: 2022-06-15 03:48:27
Subsystem:
the rest · Maintainer:
Linus Torvalds
On Tue, Jun 14, 2022 at 10:02:32PM -0400, Taylor Blau wrote:
quoted hunk ↗ jump to hunk
--- >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< ---quoted
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