Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time
From: Junio C Hamano <hidden>
Date: 2016-06-15 22:51:07
Possibly related (same subject, not in this thread)
- 2016-06-15 · [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time · Nguyễn Thái Ngọc Duy <hidden>
- 2016-06-15 · Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time · Nguyen Thai Ngoc Duy <hidden>
- 2016-06-15 · Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time · Junio C Hamano <hidden>
- 2016-06-15 · Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time · Nguyen Thai Ngoc Duy <hidden>
- 2016-06-15 · Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time · René Scharfe <hidden>
René Scharfe [off-list ref] 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 <redacted>Very nicely explained. I wish everybody wrote his log message as clearly as this. Thanks, will queue.
quoted hunk ↗ jump to hunk
--- 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'; }