scons: Put all config variables in an env['CONF'] sub-dict.

This makes what are configuration and what are internal SCons variables
explicit and separate, and makes it unnecessary to call out what
variables to export to C++.

These variables will also be plumbed into and out of kconfiglib in later
changes.

Change-Id: Iaf5e098d7404af06285c421dbdf8ef4171b3f001
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56892
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/SConscript

@@ -42,14 +42,10 @@ GTest('cprintf.test', 'cprintf.test.cc')
 Executable('cprintftime', 'cprintftime.cc', 'cprintf.cc')
 Source('debug.cc', add_tags=['gem5 trace', 'gem5 events'])
 GTest('debug.test', 'debug.test.cc', 'debug.cc')
-if env['HAVE_FENV']:
-    Source('fenv.cc')
-else:
-    warning("No IEEE FP rounding mode control.\n"
-            "FP results may deviate slightly from other platforms.")
-if env['HAVE_PNG']:
+Source('fenv.cc', tags='fenv')
+if env['CONF']['HAVE_PNG']:
     SourceLib('png')
-    Source('pngwriter.cc')
+Source('pngwriter.cc', tags='png')
 Source('fiber.cc')
 GTest('fiber.test', 'fiber.test.cc', 'fiber.cc')
 GTest('flags.test', 'flags.test.cc')
@@ -70,7 +66,7 @@ Source('pixel.cc')
 GTest('pixel.test', 'pixel.test.cc', 'pixel.cc')
 Source('pollevent.cc')
 Source('random.cc')
-if env['TARGET_ISA'] != 'null':
+if env['CONF']['TARGET_ISA'] != 'null':
     Source('remote_gdb.cc')
 Source('socket.cc')
 GTest('socket.test', 'socket.test.cc', 'socket.cc')

src/base/SConsopts

@@ -31,30 +31,35 @@ import gem5_scons
 
 with gem5_scons.Configure(main) as conf:
     # Check for <fenv.h> (C99 FP environment control)
-    conf.env['HAVE_FENV'] = conf.CheckHeader('fenv.h', '<>')
+    conf.env['CONF']['HAVE_FENV'] = conf.CheckHeader('fenv.h', '<>')
 
-    if not conf.env['HAVE_FENV']:
+    if conf.env['CONF']['HAVE_FENV']:
+        conf.env.TagImplies('fenv', 'gem5 lib')
+    else:
         warning("Header file <fenv.h> not found.\n"
                 "This host has no IEEE FP rounding mode control.")
 
     # Check for <png.h> (libpng library needed if wanting to dump
     # frame buffer image in png format)
-    conf.env['HAVE_PNG'] = conf.CheckHeader('png.h', '<>')
+    conf.env['CONF']['HAVE_PNG'] = conf.CheckHeader('png.h', '<>')
 
-    if not conf.env['HAVE_PNG']:
+    if conf.env['CONF']['HAVE_PNG']:
+        conf.env.TagImplies('png', 'gem5 lib')
+    else:
         warning("Header file <png.h> not found.\n"
                 "This host has no libpng library.\n"
                 "Disabling support for PNG framebuffers.")
 
-    have_posix_clock = \
+    conf.env['CONF']['HAVE_POSIX_CLOCK'] = \
         conf.CheckLibWithHeader([None, 'rt'], 'time.h', 'C',
                                 'clock_nanosleep(0,0,NULL,NULL);')
-    if not have_posix_clock:
+    if not conf.env['CONF']['HAVE_POSIX_CLOCK']:
         warning("Can't find library for POSIX clocks.")
 
     # Valgrind gets much less confused if you tell it when you're using
     # alternative stacks.
-    conf.env['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
+    conf.env['CONF']['HAVE_VALGRIND'] = \
+            conf.CheckCHeader('valgrind/valgrind.h')
 
 
 # Check if the compiler supports the [[gnu::deprecated]] attribute
@@ -64,20 +69,16 @@ werror_env.Append(CCFLAGS=['-Werror'])
 with gem5_scons.Configure(werror_env) as conf:
 
     # Store result in the main environment
-    main['HAVE_DEPRECATED_NAMESPACE'] = conf.TryCompile('''
+    main['CONF']['HAVE_DEPRECATED_NAMESPACE'] = conf.TryCompile('''
         int main() {return 0;}
         namespace [[gnu::deprecated("Test namespace deprecation")]]
         test_deprecated_namespace {}
     ''', '.cc')
 
-    if not main['HAVE_DEPRECATED_NAMESPACE']:
+    if not main['CONF']['HAVE_DEPRECATED_NAMESPACE']:
         warning("Deprecated namespaces are not supported by this compiler.\n"
                 "Please make sure to check the mailing list for deprecation "
                 "announcements.")
 
 sticky_vars.Add(BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks',
-                             have_posix_clock))
-
-
-export_vars.extend([
-        'HAVE_FENV', 'HAVE_PNG', 'HAVE_VALGRIND', 'HAVE_DEPRECATED_NAMESPACE'])
+                             '${CONF["HAVE_POSIX_CLOCK"]}'))

src/base/stats/SConscript

@@ -34,11 +34,10 @@ Source('info.cc')
 Source('storage.cc')
 Source('text.cc')
 
-if env['HAVE_HDF5']:
-    if env['GCC']:
-        Source('hdf5.cc', append={'CXXFLAGS': '-Wno-deprecated-copy'})
-    else:
-        Source('hdf5.cc')
+if env['GCC']:
+    Source('hdf5.cc', append={'CXXFLAGS': '-Wno-deprecated-copy'}, tags='hdf5')
+else:
+    Source('hdf5.cc', tags='hdf5')
 
 GTest('group.test', 'group.test.cc', 'group.cc', 'info.cc',
     with_tag('gem5 trace'))

src/base/stats/SConsopts

@@ -41,13 +41,13 @@ with gem5_scons.Configure(main) as conf:
     # include path and library path provided by pkg-config. We perform
     # this check even if there isn't a pkg-config configuration for hdf5
     # since some installations don't use pkg-config.
-    conf.env['HAVE_HDF5'] = \
+    conf.env['CONF']['HAVE_HDF5'] = \
             conf.CheckLibWithHeader('hdf5', 'hdf5.h', 'C',
                                     'H5Fcreate("", 0, 0, 0);') and \
             conf.CheckLibWithHeader('hdf5_cpp', 'H5Cpp.h', 'C++',
                                     'H5::H5File("", 0);')
 
-    if not conf.env['HAVE_HDF5']:
+    if conf.env['CONF']['HAVE_HDF5']:
+        conf.env.TagImplies('hdf5', 'gem5 lib')
+    else:
         warning("Couldn't find HDF5 C++ libraries. Disabling HDF5 support.")
-
-export_vars.append('HAVE_HDF5')