Tay Ray Chuan <rctay89@xxxxxxxxx> writes:
> Copying with structural assignment may not take into account that the
> LHS struct has sufficient memory, especially since the cmdname->name
> member is nonfixed in size. Be unambiguous about it by realloc()'ing it
> to be of sufficient size.
If the original code were
*(cmd->names[cj++]) = *(cmd->names[ci++]);
there may be a structural assignment involved, but
cmds->names[dst] = cmd->names[src]
just copies the pointer that points at a struct cmdname that records
the src command name to another slot of cmds->names[] array, whose
elements are pointers, no? What's there to realloc?
> @@ -58,20 +69,25 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
> {
> int ci, cj, ei;
> int cmp;
> + int last_cj;
>
> ci = cj = ei = 0;
> while (ci < cmds->cnt && ei < excludes->cnt) {
> cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name);
> if (cmp < 0)
> - cmds->names[cj++] = cmds->names[ci++];
> + copy_cmdname(&cmds->names[cj++], cmds->names[ci++]);
> else if (cmp == 0)
> ci++, ei++;
> else if (cmp > 0)
> ei++;
> }
> + last_cj = cj;
>
> while (ci < cmds->cnt)
> - cmds->names[cj++] = cmds->names[ci++];
> + copy_cmdname(&cmds->names[cj++], cmds->names[ci++]);
> +
> + while (last_cj < cmds->cnt)
> + free(cmds->names[last_cj++]);
>
> cmds->cnt = cj;
> }
We shifted cmds->names[] array to skip entries that appear in
excludes. If original cmds->names[] had "0", "1", "2", "3", ...
and excludes had "0" and "1", cmds->names[] would contain "2", "3",
"2", "3"; the first two are copied over "0" and "1" that are
excluded, and the latter two are leftover beyond last_cj. The
corresponding names share the same structure (cmds->names[] is an
array of pointers). Doesn't freeing cmds->names[2] free the
structure that is used by both cmds->names[0] and cmds->names[2]?
Confused.
The function drops cmds->names[ci] when it appears in excludes, so
you may want to free it when it happens, though.
help.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/help.c b/help.c
index 6991492..cae389b 100644
--- a/help.c
+++ b/help.c
@@ -64,9 +64,10 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name);
if (cmp < 0)
cmds->names[cj++] = cmds->names[ci++];
- else if (cmp == 0)
- ci++, ei++;
- else if (cmp > 0)
+ else if (cmp == 0) {
+ ei++;
+ free(cmd->names[ci++]);
+ } else if (cmp > 0)
ei++;
}
--
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