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commit    d25d392e89440f97bfafc0e80dc7737872659d76
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Tue Jul 01 16:40:35 2025 +0000
First released in: 16.10, 17.6, 18.0

    Make sure IOV_MAX is defined.
    
    We stopped defining IOV_MAX on non-Windows systems in 75357ab94, on
    the assumption that every non-Windows system defines it in <limits.h>
    as required by X/Open.  GNU Hurd, however, doesn't follow that
    standard either.  Put back the old logic to assume 16 if it's
    not defined.
    
    Author: Michael Banck <mbanck@gmx.net>
    Co-authored-by: Christoph Berg <myon@debian.org>
    Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
    Discussion: https://postgr.es/m/6862e8d1.050a0220.194b8d.76fa@mx.google.com
    Discussion: https://postgr.es/m/6846e0c3.df0a0220.39ef9b.c60e@mx.google.com
    Backpatch-through: 16


 src/include/port/pg_iovec.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/include/port/pg_iovec.h b/src/include/port/pg_iovec.h
index 689799c4258..5882c5b20f0 100644
--- a/src/include/port/pg_iovec.h
+++ b/src/include/port/pg_iovec.h
@@ -20,9 +20,6 @@
 
 #else
 
-/* POSIX requires at least 16 as a maximum iovcnt. */
-#define IOV_MAX 16
-
 /* Define our own POSIX-compatible iovec struct. */
 struct iovec
 {
@@ -32,6 +29,15 @@ struct iovec
 
 #endif
 
+/*
+ * If <limits.h> didn't define IOV_MAX, define our own.  X/Open requires at
+ * least 16.  (GNU Hurd apparently feel that they're not bound by X/Open,
+ * because they don't define this symbol at all.)
+ */
+#ifndef IOV_MAX
+#define IOV_MAX 16
+#endif
+
 /* Define a reasonable maximum that is safe to use on the stack. */
 #define PG_IOV_MAX Min(IOV_MAX, 32)
 


[parent: 3a2617e4f0be]