From 86c8c3306bbf02c8b0556c00986c4fdda44b3711 Mon Sep 17 00:00:00 2001
From: Kyle Gerheiser <3209794+kgerheiser@users.noreply.github.com>
Date: Tue, 9 Nov 2021 10:48:01 -0500
Subject: Add variant for the --enable-two-level-namespace option in MPICH
 (#27230)

---
 var/spack/repos/builtin/packages/mpich/package.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/var/spack/repos/builtin/packages/mpich/package.py b/var/spack/repos/builtin/packages/mpich/package.py
index cae3ea70af..16d2035959 100644
--- a/var/spack/repos/builtin/packages/mpich/package.py
+++ b/var/spack/repos/builtin/packages/mpich/package.py
@@ -81,6 +81,15 @@ spack package at this time.''',
             description='Enable Argobots support')
     variant('fortran', default=True, description='Enable Fortran support')
 
+    variant(
+        'two_level_namespace',
+        default=False,
+        description='''Build shared libraries and programs
+built with the mpicc/mpifort/etc. compiler wrappers
+with '-Wl,-commons,use_dylibs' and without
+'-Wl,-flat_namespace'.'''
+    )
+
     provides('mpi@:3.1')
     provides('mpi@:3.0', when='@:3.1')
     provides('mpi@:2.2', when='@:1.2')
@@ -475,6 +484,9 @@ spack package at this time.''',
             config_args.append('--with-thread-package=argobots')
             config_args.append('--with-argobots=' + spec['argobots'].prefix)
 
+        if '+two_level_namespace' in spec:
+            config_args.append('--enable-two-level-namespace')
+
         return config_args
 
     @run_after('install')
-- 
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