From 8961016fe70e2a05028682220f3ef0e83d503e09 Mon Sep 17 00:00:00 2001
From: Dana Robinson <43805+derobins@users.noreply.github.com>
Date: Tue, 12 Mar 2024 17:35:41 -0700
Subject: [PATCH] Update CMake comment about _POSIX_C_SOURCE (#4124)

Was missng the 2008 pread/write info
---
 config/cmake/ConfigureChecks.cmake | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index a004c768bcf..7981b647f03 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -224,7 +224,9 @@ if (CMAKE_SYSTEM_NAME MATCHES "Linux")
   # functionality so clock_gettime and CLOCK_MONOTONIC are defined
   # correctly. This was later updated to 200112L so that
   # posix_memalign() is visible for the direct VFD code on Linux
-  # systems.
+  # systems. Even later, this was changed to 200809L to support
+  # pread/pwrite in VFDs.
+  #
   # POSIX feature information can be found in the gcc manual at:
   # http://www.gnu.org/s/libc/manual/html_node/Feature-Test-Macros.html
   set (HDF_EXTRA_C_FLAGS -D_POSIX_C_SOURCE=200809L)