From ffcb3542377c62cf972ff683c101e7268332f8a0 Mon Sep 17 00:00:00 2001
From: Dana Robinson <43805+derobins@users.noreply.github.com>
Date: Wed, 25 Nov 2020 07:26:35 -0800
Subject: Minor/solaris gcc fix (#126)

* Adds gnu99 as the standard when building with gcc on Solaris

* Adds a note to RELEASE.txt and improves comments

For Solaris + gcc fix (HDFFV-11191)
---
 config/gnu-flags         | 12 ++++++++----
 release_docs/RELEASE.txt | 13 +++++++++++++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/config/gnu-flags b/config/gnu-flags
index 7cf90b8..5c6745c 100644
--- a/config/gnu-flags
+++ b/config/gnu-flags
@@ -118,12 +118,16 @@ if test "X-gcc" = "X-$cc_vendor"; then
     esac
 
     case "$host_os-$host_cpu" in
-        # cygwin needs the "-std=c99" flag removed, so make
-        # a specific case for Cygwin without the flag and a default
-        # case to add the flag everywhere else
+        # Cygwin needs the "-std=c99" flag removed.
         cygwin-*)
             ;;
-
+        # On Solaris, gcc needs the gnu99 standard to pick up certain POSIX
+        # things. Do NOT use this as the gcc norm as this encourages the use
+        # of non-standard gcc extensions.
+        *solaris*)
+            H5_CFLAGS="$H5_CFLAGS -std=gnu99"
+            ;;
+        # Everybody else gets c99 as the standard.
         *)
             H5_CFLAGS="$H5_CFLAGS -std=c99"
             ;;
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 67fbe51..690635a 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -47,6 +47,19 @@ New Features
 
     Configuration:
     -------------
+    - Fixed POSIX problems when building w/ gcc on Solaris
+
+      When building on Solaris using gcc, the POSIX symbols were not
+      being set correctly, which could lead to issues like clock_gettime()
+      not being found.
+
+      The standard is now set to gnu99 when building with gcc on Solaris,
+      which allows POSIX things to be #defined and linked correctly. This
+      differs slightly from the gcc norm, where we set the standard to c99
+      and manually set POSIX #define symbols.
+
+      (DER - 2020/11/25, HDFFV-11191)
+
     - Added a configure-time option to consider certain compiler warnings
       as errors
 
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