Renà Scharfe <rene.scharfe@xxxxxxxxxxxxxx> writes:
> Subject: strbuf: clarify assertion in strbuf_setlen()
>
> Commit a8f3e2219 introduced the strbuf_grow() call to strbuf_setlen() to
> make ensure that there was at least one byte available to write the
> mandatory trailing NUL, even for previously unallocated strbufs.
>
> Then b315c5c0 added strbuf_slopbuf for the same reason, only globally for
> all uses of strbufs.
>
> Thus the strbuf_grow() call can be removed now. This avoids readers of
> strbuf.h from mistakenly thinking that strbuf_setlen() can be used to
> extend a strbuf.
>
> The following assert() needs to be changed to cope with the fact that
> sb->alloc can now be zero, which is OK as long as len is also zero. As
> suggested by Junio, use the chance to convert it to a die() with a short
> explanatory message. The pattern of 'die("BUG: ...")' is already used in
> strbuf.c.
>
> This was the only assert() in strbuf.[ch], so assert.h doesn't have to be
> included anymore either.
>
> Signed-off-by: Rene Scharfe <rene.scharfe@xxxxxxxxxxxxxx>
Very nicely explained. I wish everybody wrote his log message as clearly
as this.
Thanks, will queue.
> ---
> strbuf.h | 7 ++-----
> 1 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/strbuf.h b/strbuf.h
> index 07060ce..9e6d9fa 100644
> --- a/strbuf.h
> +++ b/strbuf.h
> @@ -3,8 +3,6 @@
>
> /* See Documentation/technical/api-strbuf.txt */
>
> -#include <assert.h>
> -
> extern char strbuf_slopbuf[];
> struct strbuf {
> size_t alloc;
> @@ -33,9 +31,8 @@ static inline size_t strbuf_avail(const struct strbuf *sb) {
> extern void strbuf_grow(struct strbuf *, size_t);
>
> static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
> - if (!sb->alloc)
> - strbuf_grow(sb, 0);
> - assert(len < sb->alloc);
> + if (len > (sb->alloc ? sb->alloc - 1 : 0))
> + die("BUG: strbuf_setlen() beyond buffer");
> sb->len = len;
> sb->buf[len] = '\0';
> }
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