support: Change xgetline to return 0 on EOF

The advantage is that the buffer will always contain the number
of characters as returned from the function, which allows one to use
a sequence like

  /* No more audit module output.  */
  line_length = xgetline (&buffer, &buffer_length, fp);
  TEST_COMPARE_BLOB ("", 0, buffer, line_length);

to check for an expected EOF, while also reporting any unexpected
extra data encountered.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/support/xstdio.h b/support/xstdio.h
index 143957b6a8..807c3afc43 100644
--- a/support/xstdio.h
+++ b/support/xstdio.h
@@ -27,7 +27,10 @@ __BEGIN_DECLS
 FILE *xfopen (const char *path, const char *mode);
 void xfclose (FILE *);
 
-ssize_t xgetline (char **lineptr, size_t *n, FILE *stream);
+/* Read a line from FP, using getline.  *BUFFER must be NULL, or a
+   heap-allocated pointer of *LENGTH bytes.  Return the number of
+   bytes in the line if a line was read, or 0 on EOF.  */
+size_t xgetline (char **lineptr, size_t *n, FILE *stream);
 
 __END_DECLS