split: avoid failure due to leftover 'errno' value

* src/split.c (lines_chunk_split): Fix logic bug that led to
unwarranted failure of "split -n l/2 /dev/zero" on NetBSD 5.1.
The same would happen when splitting a growing file, where
open/lseek-end gives one size, but by the time we read, there
is more data available.
(bytes_chunk_extract): Likewise.
* NEWS (Bug fixes): Mention this.
* tests/split/l-chunk: The latter case was not exercised.
Add code to do that.
Bug introduced with the chunk-selecting feature in v8.7-25-gbe10739.

Co-authored-by: Jim Meyering <meyering@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/split.c b/src/split.c
index 5b00fe804..2eb343b15 100644
--- a/src/split.c
+++ b/src/split.c
@@ -623,11 +623,11 @@ lines_chunk_split (uintmax_t k, uintmax_t n, char *buf, size_t bufsize,
     {
       char *bp = buf, *eob;
       size_t n_read = full_read (STDIN_FILENO, buf, bufsize);
-      n_read = MIN (n_read, file_size - n_written);
       if (n_read < bufsize && errno)
         error (EXIT_FAILURE, errno, "%s", infile);
       else if (n_read == 0)
         break; /* eof.  */
+      n_read = MIN (n_read, file_size - n_written);
       chunk_truncated = false;
       eob = buf + n_read;
 
@@ -718,11 +718,11 @@ bytes_chunk_extract (uintmax_t k, uintmax_t n, char *buf, size_t bufsize,
   while (start < end)
     {
       size_t n_read = full_read (STDIN_FILENO, buf, bufsize);
-      n_read = MIN (n_read, end - start);
       if (n_read < bufsize && errno)
         error (EXIT_FAILURE, errno, "%s", infile);
       else if (n_read == 0)
         break; /* eof.  */
+      n_read = MIN (n_read, end - start);
       if (full_write (STDOUT_FILENO, buf, n_read) != n_read
           && ! ignorable (errno))
         error (EXIT_FAILURE, errno, "%s", quote ("-"));