getline.3: !*lineptr is sufficient

No implementation or spec requires *n to be 0 to allocate a new buffer:
  * musl checks for !*lineptr
    (and sets *n=0 for later allocations)
  * glibc checks for !*lineptr || !*n
    (but only because it allocates early)
  * NetBSD checks for !*lineptr
    (and sets *n=0 for later allocations)
    (but specifies *n => mlen(*lineptr) >= *n as a precondition,
     to which this appears to be an exception)
  * FreeBSD checks for !*lineptr and sets *n=0
    (and specifies !*lineptr as sufficient)
  * Lastly, POSIX.1-2017 specifies:
    > If *n is non-zero, the application shall ensure that *lineptr
    > either points to an object of size at least *n bytes,
    > or is a null pointer.

The new wording matches POSIX, even if it arrives at the point slightly
differently

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man3/getline.3 b/man3/getline.3
index a32d7e770e810c97c8cfe0e743cc611260024695..6641ecc3568df92f0e5d3bacc0fb51197bc225ff 100644 (file)
--- a/man3/getline.3
+++ b/man3/getline.3
@@ -59,9 +59,7 @@ one was found.
 .PP
 If
 .I "*lineptr"
-is set to NULL and
-.I *n
-is set 0 before the call, then
+is set to NULL before the call, then
 .BR getline ()
 will allocate a buffer for storing the line.
 This buffer should be freed by the user program