git/string-list.h
Michael Haggerty ac7da78ede for_each_string_list_item: avoid undefined behavior for empty list
If you pass a newly initialized or newly cleared `string_list` to
`for_each_string_list_item()`, then the latter does

    for (
            item = (list)->items; /* NULL */
            item < (list)->items + (list)->nr; /* NULL + 0 */
            ++item)

Even though this probably works almost everywhere, it is undefined
behavior, and it could plausibly cause highly-optimizing compilers to
misbehave.  C99 section 6.5.6 paragraph 8 explains:

    If both the pointer operand and the result point to elements
    of the same array object, or one past the last element of the
    array object, the evaluation shall not produce an overflow;
    otherwise, the behavior is undefined.

and (6.3.2.3.3) a null pointer does not point to anything.

Guard the loop with a NULL check to make the intent crystal clear to
even the most pedantic compiler.  A suitably clever compiler could let
the NULL check only run in the first iteration, but regardless, this
overhead is likely to be dwarfed by the work to be done on each item.

This problem was noticed by Coverity.

[jn: using a NULL check instead of a placeholder empty list;
 fleshed out the commit message based on mailing list discussion]

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-20 14:41:08 +09:00

140 lines
5.4 KiB
C

#ifndef STRING_LIST_H
#define STRING_LIST_H
struct string_list_item {
char *string;
void *util;
};
typedef int (*compare_strings_fn)(const char *, const char *);
struct string_list {
struct string_list_item *items;
unsigned int nr, alloc;
unsigned int strdup_strings:1;
compare_strings_fn cmp; /* NULL uses strcmp() */
};
#define STRING_LIST_INIT_NODUP { NULL, 0, 0, 0, NULL }
#define STRING_LIST_INIT_DUP { NULL, 0, 0, 1, NULL }
void string_list_init(struct string_list *list, int strdup_strings);
void print_string_list(const struct string_list *p, const char *text);
void string_list_clear(struct string_list *list, int free_util);
/* Use this function to call a custom clear function on each util pointer */
/* The string associated with the util pointer is passed as the second argument */
typedef void (*string_list_clear_func_t)(void *p, const char *str);
void string_list_clear_func(struct string_list *list, string_list_clear_func_t clearfunc);
/* Use this function or the macro below to iterate over each item */
typedef int (*string_list_each_func_t)(struct string_list_item *, void *);
int for_each_string_list(struct string_list *list,
string_list_each_func_t, void *cb_data);
#define for_each_string_list_item(item,list) \
for (item = (list)->items; \
item && item < (list)->items + (list)->nr; \
++item)
/*
* Apply want to each item in list, retaining only the ones for which
* the function returns true. If free_util is true, call free() on
* the util members of any items that have to be deleted. Preserve
* the order of the items that are retained.
*/
void filter_string_list(struct string_list *list, int free_util,
string_list_each_func_t want, void *cb_data);
/*
* Remove any empty strings from the list. If free_util is true, call
* free() on the util members of any items that have to be deleted.
* Preserve the order of the items that are retained.
*/
void string_list_remove_empty_items(struct string_list *list, int free_util);
/* Use these functions only on sorted lists: */
int string_list_has_string(const struct string_list *list, const char *string);
int string_list_find_insert_index(const struct string_list *list, const char *string,
int negative_existing_index);
/*
* Inserts the given string into the sorted list.
* If the string already exists, the list is not altered.
* Returns the string_list_item, the string is part of.
*/
struct string_list_item *string_list_insert(struct string_list *list, const char *string);
/*
* Removes the given string from the sorted list.
* If the string doesn't exist, the list is not altered.
*/
extern void string_list_remove(struct string_list *list, const char *string,
int free_util);
/*
* Checks if the given string is part of a sorted list. If it is part of the list,
* return the coresponding string_list_item, NULL otherwise.
*/
struct string_list_item *string_list_lookup(struct string_list *list, const char *string);
/*
* Remove all but the first of consecutive entries with the same
* string value. If free_util is true, call free() on the util
* members of any items that have to be deleted.
*/
void string_list_remove_duplicates(struct string_list *sorted_list, int free_util);
/* Use these functions only on unsorted lists: */
/*
* Add string to the end of list. If list->strdup_string is set, then
* string is copied; otherwise the new string_list_entry refers to the
* input string.
*/
struct string_list_item *string_list_append(struct string_list *list, const char *string);
/*
* Like string_list_append(), except string is never copied. When
* list->strdup_strings is set, this function can be used to hand
* ownership of a malloc()ed string to list without making an extra
* copy.
*/
struct string_list_item *string_list_append_nodup(struct string_list *list, char *string);
void string_list_sort(struct string_list *list);
int unsorted_string_list_has_string(struct string_list *list, const char *string);
struct string_list_item *unsorted_string_list_lookup(struct string_list *list,
const char *string);
void unsorted_string_list_delete_item(struct string_list *list, int i, int free_util);
/*
* Split string into substrings on character delim and append the
* substrings to list. The input string is not modified.
* list->strdup_strings must be set, as new memory needs to be
* allocated to hold the substrings. If maxsplit is non-negative,
* then split at most maxsplit times. Return the number of substrings
* appended to list.
*
* Examples:
* string_list_split(l, "foo:bar:baz", ':', -1) -> ["foo", "bar", "baz"]
* string_list_split(l, "foo:bar:baz", ':', 0) -> ["foo:bar:baz"]
* string_list_split(l, "foo:bar:baz", ':', 1) -> ["foo", "bar:baz"]
* string_list_split(l, "foo:bar:", ':', -1) -> ["foo", "bar", ""]
* string_list_split(l, "", ':', -1) -> [""]
* string_list_split(l, ":", ':', -1) -> ["", ""]
*/
int string_list_split(struct string_list *list, const char *string,
int delim, int maxsplit);
/*
* Like string_list_split(), except that string is split in-place: the
* delimiter characters in string are overwritten with NULs, and the
* new string_list_items point into string (which therefore must not
* be modified or freed while the string_list is in use).
* list->strdup_strings must *not* be set.
*/
int string_list_split_in_place(struct string_list *list, char *string,
int delim, int maxsplit);
#endif /* STRING_LIST_H */