On Sat, Aug 17, 2013 at 02:40:05PM +0200, Steffen Prohaska wrote:
> Previously, filtering more than 2GB through an external filter (see
> test) failed on Mac OS X 10.8.4 (12E55) with:
>
> error: read from external filter cat failed
> error: cannot feed the input to external filter cat
> error: cat died of signal 13
> error: external filter cat failed 141
> error: external filter cat failed
>
> The reason is that read() immediately returns with EINVAL if len >= 2GB.
> I haven't found any information under which specific conditions this
> occurs. My suspicion is that it happens when reading from a pipe, while
> reading from a standard file should always be fine. I haven't tested
> any other version of Mac OS X, though I'd expect that other versions are
> affected as well.
>
> The problem is fixed by always reading less than 2GB in xread().
> xread() doesn't guarantee to read all the requested data at once, and
> callers are expected to gracefully handle partial reads. Slicing large
> reads into 2GB pieces should not hurt practical performance.
>
> Signed-off-by: Steffen Prohaska <proha...@zib.de>
> ---
> t/t0021-conversion.sh | 9 +++++++++
> wrapper.c | 8 ++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/t/t0021-conversion.sh b/t/t0021-conversion.sh
> index e50f0f7..aec1253 100755
> --- a/t/t0021-conversion.sh
> +++ b/t/t0021-conversion.sh
> @@ -190,4 +190,13 @@ test_expect_success 'required filter clean failure' '
> test_must_fail git add test.fc
> '
>
> +test_expect_success 'filter large file' '
> + git config filter.largefile.smudge cat &&
> + git config filter.largefile.clean cat &&
> + dd if=/dev/zero of=2GB count=2097152 bs=1024 &&
> + echo "/2GB filter=largefile" >.gitattributes &&
> + git add 2GB 2>err &&
> + ! grep -q "error" err
> +'
> +
> test_done
> diff --git a/wrapper.c b/wrapper.c
> index 6a015de..2a2f496 100644
> --- a/wrapper.c
> +++ b/wrapper.c
> @@ -139,6 +139,14 @@ ssize_t xread(int fd, void *buf, size_t len)
> {
> ssize_t nr;
> while (1) {
> +#ifdef __APPLE__
> + const size_t twoGB = (1l << 31);
> + /* len >= 2GB immediately fails on Mac OS X with EINVAL when
> + * reading from pipe. */
> + if (len >= twoGB) {
> + len = twoGB - 1;
> + }
Please don't use unnecessary curly braces here (see
Documentation/CodingGuidelines).
> +#endif
> nr = read(fd, buf, len);
> if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
> continue;
> --
> 1.8.4.rc3.5.gfcb973a
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