Re: [PATCH v2 5/5] convert: add filter.<driver>.process option
- From
- Eric Wong <e@80x24.org>
- Date
- Jul 27, 2016, 09:41 UTC
- Message-ID
- <20160727094102.GA31374@starla>
- In-Reply-To
- <20160727000605.49982-6-larsxschneider@gmail.com>
larsxschneider@gmail.com wrote:
> +static off_t multi_packet_read(struct strbuf *sb, const int fd, const size_t size)
I'm no expert in C, but this might be const-correctness taken too far. I think basing this on the read(2) prototype is less surprising:
static ssize_t multi_packet_read(int fd, struct strbuf *sb, size_t size)
Also what Jeff said about off_t vs size_t, but my previous emails may have confused you w.r.t. off_t usage...
> +static int multi_packet_write(const char *src, size_t len, const int in, const int out)
Same comment about over const ints above. len can probably be off_t based on what is below; but you need to process the loop in ssize_t-friendly chunks.
Show 5 quoted lines
> +{
> + int ret = 1;
> + char header[4];
> + char buffer[8192];
> + off_t bytes_to_write;What Jeff said, this should be ssize_t to match read(2) and xread
Show 12 quoted lines
> + while (ret) {
> + if (in >= 0) {
> + bytes_to_write = xread(in, buffer, sizeof(buffer));
> + if (bytes_to_write < 0)
> + ret &= 0;
> + src = buffer;
> + } else {
> + bytes_to_write = len > LARGE_PACKET_MAX - 4 ? LARGE_PACKET_MAX - 4 : len;
> + len -= bytes_to_write;
> + }
> + if (!bytes_to_write)
> + break;The whole ret &= .. style error handling is hard-to-follow and here, a source of bugs. I think the expected convention on hitting errors is:
1) stop whatever you're doing 2) cleanup 3) propagate the error to callers
"goto" is an acceptable way of accomplishing this.
For example, byte_to_write may still be negative at this point (and interpreted as a really big number when cast to unsigned size_t) and src/buffer could be stack garbage.
Show 8 quoted lines
> + set_packet_header(header, bytes_to_write + 4); > + ret &= write_in_full(out, &header, sizeof(header)) == sizeof(header); > + ret &= write_in_full(out, src, bytes_to_write) == bytes_to_write; > + } > + ret &= write_in_full(out, "0000", 4) == 4; > + return ret; > +} > +
> +static int apply_protocol_filter(const char *path, const char *src, size_t len,
> + int fd, struct strbuf *dst, const char *cmd,
> + const char *filter_type)
> +{<snip>
> + if (fd >= 0 && !src) {
> + ret &= fstat(fd, &file_stat) != -1;
> + len = file_stat.st_size;Same truncation bug I noticed earlier; what I originally meant is the `len' arg probably ought to be off_t, here, not size_t. 32-bit x86 Linux systems have 32-bit size_t (unsigned), but large file support means off_t is 64-bits (signed).
Also, is it worth continuing this function if fstat fails?
Show 7 quoted lines
> + } > + > + sigchain_push(SIGPIPE, SIG_IGN); > + > + packet_write(process->in, "%s\n", filter_type); > + packet_write(process->in, "%s\n", path); > + packet_write(process->in, "%zu\n", len);
I'm not sure if "%zu" is portable since we don't do C99 (yet?) For 64-bit signed off_t, you can probably do:
packet_write(process->in, "%"PRIuMAX"\n", (uintmax_t)len);
Since we don't have PRIiMAX or intmax_t, here, and a negative len would be a bug (probably from failed fstat) anyways.
> + ret &= multi_packet_write(src, len, fd, process->in);
multi_packet_write will probably fail if fstat failed above...
> + strbuf = packet_read_line(process->out, NULL);
And this may just block or timeout if multi_packet_write failed.
Naptime, I may look at the rest another day.