Use system-installed version of fmt library if available

Resolves #348.

SConstruct

@@ -412,6 +412,12 @@ config_options = [
         """Select whether to use Eigen from a system installation ('y'), from
            a git submodule ('n'), or to decide automatically ('default').""",
         'default', ('default', 'y', 'n')),
+    EnumVariable(
+        'system_fmt',
+        """Select whether to use the fmt library from a system installation
+           ('y'), from a git submodule ('n'), or to decide automatically
+           ('default').""",
+        'default', ('default', 'y', 'n')),
     EnumVariable(
         'system_sundials',
         """Select whether to use Sundials from a system installation ('y'), from
@@ -730,19 +736,32 @@ if not conf.CheckCXXHeader('cmath', '<>'):
     config_error('The C++ compiler is not correctly configured.')
 
 # Check for fmt library and checkout submodule if needed
-if not os.path.exists('ext/fmt/fmt/format.h'):
-    if not os.path.exists('.git'):
-        config_error('fmt is missing. Install source in ext/fmt.')
+# Test for 'ostream.h' to ensure that version >= 3.0.0 is available
+if env['system_fmt'] in ('y', 'default'):
+    if conf.CheckCXXHeader('fmt/ostream.h', '""'):
+        env['system_fmt'] = True
+        print """INFO: Using system installation of fmt library."""
+
+    elif env['system_fmt'] == 'y':
+        config_error('Expected system installation of fmt library, but it '
+            'could not be found.')
+
+if env['system_fmt'] in ('n', 'default'):
+    env['system_fmt'] = False
+    print """INFO: Using private installation of fmt library."""
+    if not os.path.exists('ext/fmt/fmt/format.h'):
+        if not os.path.exists('.git'):
+            config_error('fmt is missing. Install source in ext/fmt.')
 
-    try:
-        code = subprocess.call(['git','submodule','update','--init',
-                                '--recursive','ext/fmt'])
-    except Exception:
-        code = -1
-    if code:
-        config_error('fmt submodule checkout failed.\n'
-                     'Try manually checking out the submodule with:\n\n'
-                     '    git submodule update --init --recursive ext/fmt\n')
+        try:
+            code = subprocess.call(['git','submodule','update','--init',
+                                    '--recursive','ext/fmt'])
+        except Exception:
+            code = -1
+        if code:
+            config_error('fmt submodule checkout failed.\n'
+                         'Try manually checking out the submodule with:\n\n'
+                         '    git submodule update --init --recursive ext/fmt\n')
 
 # Check for googletest and checkout submodule if needed
 if env['system_googletest'] in ('y', 'default'):
@@ -1242,6 +1261,7 @@ cdefine('FTN_TRAILING_UNDERSCORE', 'lapack_ftn_trailing_underscore')
 cdefine('LAPACK_NAMES_LOWERCASE', 'lapack_names', 'lower')
 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',
@@ -1335,6 +1355,10 @@ if env['blas_lapack_libs']:
     linkLibs.extend(env['blas_lapack_libs'])
     linkSharedLibs.extend(env['blas_lapack_libs'])
 
+if env['system_fmt']:
+    linkLibs.append('fmt')
+    linkSharedLibs.append('fmt')
+
 # Store the list of needed static link libraries in the environment
 env['cantera_libs'] = linkLibs
 env['cantera_shared_libs'] = linkSharedLibs

ext/SConscript

@@ -26,12 +26,11 @@ def prep_gtest(env):
 def prep_fmt(env):
     localenv = prep_default(env)
     license_files.append(('fmtlib', 'fmt/LICENSE.rst'))
-    build(localenv.Command("#include/cantera/ext/fmt/format.h",
-                           "#ext/fmt/fmt/format.h",
-                           Copy('$TARGET', '$SOURCE')))
-    build(localenv.Command("#include/cantera/ext/fmt/ostream.h",
-                           "#ext/fmt/fmt/ostream.h",
-                           Copy('$TARGET', '$SOURCE')))
+    if not env['system_fmt']:
+        for name in ('format.h', 'ostream.h'):
+            build(localenv.Command("#include/cantera/ext/fmt/" + name,
+                                   "#ext/fmt/fmt/" + name,
+                                    Copy('$TARGET', '$SOURCE')))
     return localenv
 
 # each element of libs is: (subdir, (file extensions), prepfunction)

include/cantera/base/config.h.in

@@ -43,6 +43,7 @@ typedef int ftnlen;       // Fortran hidden string length type
 %(CT_USE_LAPACK)s
 
 %(CT_USE_SYSTEM_EIGEN)s
+%(CT_USE_SYSTEM_FMT)s
 
 //--------- operating system --------------------------------------
 

include/cantera/base/ctexceptions.h

@@ -9,9 +9,8 @@
 #ifndef CT_CTEXCEPTIONS_H
 #define CT_CTEXCEPTIONS_H
 
+#include "cantera/base/fmt.h"
 #include <exception>
-#include <string>
-#include "cantera/ext/fmt/format.h"
 
 namespace Cantera
 {

include/cantera/base/fmt.h

@@ -0,0 +1,10 @@
+//! @file fmt.h Wrapper for either system-installed or local headers for fmt
+#include "ct_defs.h"
+
+#if CT_USE_SYSTEM_FMT
+  #include "fmt/format.h"
+  #include "fmt/ostream.h"
+#else
+  #include "cantera/ext/fmt/format.h"
+  #include "cantera/ext/fmt/ostream.h"
+#endif

include/cantera/base/global.h

@@ -18,7 +18,7 @@
 #define CT_GLOBAL_H
 
 #include "ct_defs.h"
-#include "cantera/ext/fmt/format.h"
+#include "cantera/base/fmt.h"
 
 namespace Cantera
 {

include/cantera/base/stringUtils.h

@@ -8,7 +8,7 @@
 #define CT_STRINGUTILS_H
 
 #include "ct_defs.h"
-#include "cantera/ext/fmt/format.h"
+#include "cantera/base/fmt.h"
 
 #include <string>
 

src/SConscript

@@ -49,6 +49,8 @@ if localenv['OS'] in ('Darwin', 'Windows', 'Cygwin'):
     if localenv['blas_lapack_libs']:
         localenv.Append(LIBS=localenv['blas_lapack_libs'],
                         LIBPATH=localenv['blas_lapack_dir'])
+    if localenv['system_fmt']:
+        localenv.Append(LIBS='fmt')
 
 # Build the Cantera shared library
 if localenv['layout'] != 'debian':

test_problems/surfSolverTest/surfaceSolver.cpp

@@ -18,7 +18,7 @@
 #include "cantera/kinetics.h"
 #include "cantera/kinetics/ImplicitSurfChem.h"
 #include "cantera/kinetics/solveSP.h"
-#include "cantera/ext/fmt/ostream.h"
+#include "cantera/base/fmt.h"
 #include <cstdio>
 #include <fstream>
 

test_problems/surfSolverTest/surfaceSolver2.cpp

@@ -27,7 +27,7 @@ static void printUsage()
 #include "cantera/kinetics.h"
 #include "cantera/kinetics/ImplicitSurfChem.h"
 #include "cantera/kinetics/solveSP.h"
-#include "cantera/ext/fmt/ostream.h"
+#include "cantera/base/fmt.h"
 #include <cstdio>
 #include <fstream>