string-list: document iterator behavior on NULL input

The for_each_string_list_item() macro takes a string_list and
automatically constructs a for loop to iterate over its contents. This
macro will segfault if the list is non-NULL.

We cannot change the macro to be careful around NULL values because
there are many callers that use the address of a local variable, which
will never be NULL and will cause compile errors with -Werror=address.

For now, leave a documentation comment to try to avoid mistakes in the
future where a caller does not check for a NULL list.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2022-09-27 13:57:01 +00:00 committed by Junio C Hamano
parent 50a044f1e4
commit d151f0cce7
1 changed files with 6 additions and 1 deletions

View File

@ -141,7 +141,12 @@ 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);
/** Iterate over each item, as a macro. */
/**
* Iterate over each item, as a macro.
*
* Be sure that 'list' is non-NULL. The macro cannot perform NULL
* checks due to -Werror=address errors.
*/
#define for_each_string_list_item(item,list) \
for (item = (list)->items; \
item && item < (list)->items + (list)->nr; \