There are a number of places in the code where we call sprintf(), with the assumption that the output will fit into the buffer. In many cases this is true (e.g., formatting a number into a large buffer), but it is hard to tell immediately from looking at the code. It would be nice if we had some run-time check to make sure that our assumption is correct (and to communicate to readers of the code that we are not blindly calling sprintf, but have actually thought about this case).
This patch introduces xsnprintf, which behaves just like snprintf, except that it dies whenever the output is truncated. This acts as a sort of assert() for these cases, which can help find places where the assumption is violated (as opposed to truncating and proceeding, which may just silently give a wrong answer). Signed-off-by: Jeff King <p...@peff.net> --- git-compat-util.h | 3 +++ wrapper.c | 16 ++++++++++++++++ 2 files changed, 19 insertions(+) diff --git a/git-compat-util.h b/git-compat-util.h index f649e81..348b9dc 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -744,6 +744,9 @@ static inline size_t xsize_t(off_t len) return (size_t)len; } +__attribute__((format (printf, 3, 4))) +extern int xsnprintf(char *dst, size_t max, const char *fmt, ...); + /* in ctype.c, for kwset users */ extern const unsigned char tolower_trans_tbl[256]; diff --git a/wrapper.c b/wrapper.c index 0e22d43..6fcaa4d 100644 --- a/wrapper.c +++ b/wrapper.c @@ -621,6 +621,22 @@ char *xgetcwd(void) return strbuf_detach(&sb, NULL); } +int xsnprintf(char *dst, size_t max, const char *fmt, ...) +{ + va_list ap; + int len; + + va_start(ap, fmt); + len = vsnprintf(dst, max, fmt, ap); + va_end(ap); + + if (len < 0) + die("BUG: your snprintf is broken"); + if (len >= max) + die("BUG: attempt to snprintf into too-small buffer"); + return len; +} + static int write_file_v(const char *path, int fatal, const char *fmt, va_list params) { -- 2.6.0.rc3.454.g204ad51 -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html