From 2a8ac433088fb12dff087fe6bf6a92369ecc7bb4 Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Fri, 28 Oct 2016 12:37:45 -0400
Subject: [PATCH] [SCons] Add fmt.h to system.h and improve PCH dependency
 handling

---
 SConstruct                    | 13 +++++++++----
 include/cantera/base/system.h |  1 +
 src/SConscript                | 12 ++++++++----
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/SConstruct b/SConstruct
index 149799fcc..35aea8563 100644
--- a/SConstruct
+++ b/SConstruct
@@ -60,6 +60,7 @@ if 'clean' in COMMAND_LINE_TARGETS:
     removeDirectory('.sconf_temp')
     removeFile('.sconsign.dblite')
     removeFile('include/cantera/base/config.h')
+    removeFile('include/cantera/base/config.h.build')
     removeFile('include/cantera/base/system.h.gch')
     removeFile('include/cantera/base/system.pch')
     removeFile('include/cantera/base/system.obj')
@@ -1308,11 +1309,15 @@ cdefine('CT_USE_LAPACK', 'use_lapack')
 cdefine('CT_USE_SYSTEM_EIGEN', env['system_eigen'])
 cdefine('CT_USE_SYSTEM_FMT', 'system_fmt')
 
-config_h = env.Command('include/cantera/base/config.h',
-                       'include/cantera/base/config.h.in',
+config_h_build = env.Command('include/cantera/base/config.h.build',
+                             'include/cantera/base/config.h.in',
                        ConfigBuilder(configh))
-env.AlwaysBuild(config_h)
-
+# This separate copy operation, which SCons will skip of config.h.build is
+# unmodified, prevents unnecessary rebuilds of the precompiled header
+config_h = env.Command('include/cantera/base/config.h',
+                       'include/cantera/base/config.h.build',
+                       Copy('$TARGET', '$SOURCE'))
+env.AlwaysBuild(config_h_build)
 env['config_h_target'] = config_h
 
 # *********************
diff --git a/include/cantera/base/system.h b/include/cantera/base/system.h
index e2a41d8b0..13d35240d 100644
--- a/include/cantera/base/system.h
+++ b/include/cantera/base/system.h
@@ -15,5 +15,6 @@
 #include <memory>
 
 #include <boost/algorithm/string.hpp>
+#include "fmt.h"
 
 #endif
diff --git a/src/SConscript b/src/SConscript
index 3d5a7766c..7bd323b76 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -34,24 +34,28 @@ if env['CC'] == 'cl' and env['debug']:
 if env['use_pch']:
     if env['CC'] == 'cl':
         localenv['PCH'], pchobj = localenv.PCH('#include/cantera/base/system.cpp')
+        pch = localenv['PCH']
         libraryTargets.append(pchobj)
         localenv['PCHSTOP'] = 'cantera/base/system.h'
     else:
         localenv['precompiled_header'] = File('#include/cantera/base/system.h')
-        pch = build(localenv.GchSh('#include/cantera/base/system.h.gch',
-                              localenv['precompiled_header']))
-        # To force early compilaton of the precompiled header
-        localenv.Depends(env['config_h_target'], pch)
+        pch = localenv.GchSh('#include/cantera/base/system.h.gch',
+                              localenv['precompiled_header'])
+        # # To force early compilaton of the precompiled header
+        # localenv.Depends(env['config_h_target'], pch)
 
 else:
     removeFile('include/cantera/base/system.h.gch')
     env['pch_flags'] = []
+    pch = None
 
 for subdir, extensions, setup in libs:
     env2 = localenv.Clone()
     source = setup(env2, subdir, extensions)
     objects = env2.SharedObject(source)
     env2.Depends(objects, env2['config_h_target'])
+    if pch:
+        env2.Depends(objects, pch)
     libraryTargets.extend(objects)