Merge branch 'mnt/c++standard' into 'master'

Clean up construction of compiler flags

See merge request fsl/base!4

config/common/buildSettings.mk → config/buildSettings.mk

-# This master make file is based on the "old"
-# systemvars.mk and externallibs.mk files from:
-# 	apple-darwin13-llvm6.0
-# 	linux_64-gcc4.4
-# 	linux_64-gcc4.8
+# This file defines architecture specific commands and compiler flags.
+# It is included before vars.mk, which uses the ARCH* compiler flags
+# to construct the final compiler flag variables that are used in C/C++
+# compilation.
 
 # get system type (Darwin, Linux)
 SYSTYPE := $(shell uname -s)
@@ -27,17 +26,26 @@ TCLSH   ?= ${FSLDIR}/bin/fsltclsh
 #
 #####################################################################
 
-# All platform specific compiler/linker options are added to
-# the following variables. They are populated in the platform-
-# specific branches below. Final values for CFLAGS, CXXFLAGS,
-# and LDFLAGS (including include/library search paths) are
-# constructed in common/vars.mk
+# Platform specific compiler/linker options may be added to
+# the following ARCH* variables. These variables are *always*
+# added to compiler calls.
+#
+# Final values for CFLAGS, CXXFLAGS, and LDFLAGS (including
+# include/library search paths) are constructed in vars.mk.
+#
+# The ARCH* variables here are added to the end of the final
+# FLAGS variables, which means that any options specified here
+# will usually take precedence over options provided by the
+# environment.
 
 # Compiler flags for C projects
-ARCHCFLAGS =
+ARCHCFLAGS = -std=c99
 
 # Compiler flags for C++ projects.
-ARCHCXXFLAGS = -D_GLIBCXX_USE_CXX11_ABI=0
+ARCHCXXFLAGS = -std=c++11
+
+# Preprocesor flags for C/C++ projects.
+ARCHCPPFLAGS =
 
 # Linker flags for all projects
 ARCHLDFLAGS =
@@ -51,6 +59,13 @@ ARCHNVCCFLAGS =
 # Linker flags for CUDA projects.
 ARCHNVCCLDFLAGS =
 
+# Allow flags to be provided by the environment.
+# Default CC, CXX, CFLAGS, CXXFLAGS, and LDFLAGS
+# are set in the platform-specific sections below.
+CPPFLAGS    ?=
+NVCCFLAGS   ?=
+NVCCLDFLAGS ?=
+
 #####################################################################
 #
 # Darwin specific sys vars and ext libs
@@ -58,15 +73,14 @@ ARCHNVCCLDFLAGS =
 #####################################################################
 ifeq ($(SYSTYPE), Darwin)
 
-  # Commands
-  CC  ?= cc
-  CXX ?= c++
-
-  # Compiler flags
-  ARCHCXXFLAGS += -arch x86_64 -Wall -pedantic -fPIC
-  ARCHCFLAGS   += $(ARCHCXXFLAGS) -std=c99
-  ARCHLDFLAGS  += -Wl,-search_paths_first
-  ARCHLIBS     += -llapack -lblas -lz -lm
+  # Compiler flags. CC, CXX, CFLAGS, CXXFLAGS, and
+  # LDFLAGS may be overridden by the environment.
+  CC       ?= clang
+  CXX      ?= clang++
+  CFLAGS   ?= -arch x86_64 -Wall -pedantic -fPIC
+  CXXFLAGS ?= -arch x86_64 -Wall -pedantic -fPIC
+  LDFLAGS  ?= -Wl,-search_paths_first
+  ARCHLIBS += -llapack -lblas -lz -lm
 endif
 
 #####################################################################
@@ -76,16 +90,15 @@ endif
 #####################################################################
 ifeq ($(SYSTYPE), Linux)
 
- # Commands
-  CC  ?= gcc
-  CXX ?= c++
-
-  # Compiler flags
-  ARCHCFLAGS   += -fexpensive-optimizations \
+  # Compiler flags. CC, CXX, CFLAGS, CXXFLAGS, and
+  # LDFLAGS may be overridden by the environment.
+  CC       ?= gcc
+  CXX      ?= g++
+  CFLAGS   ?= -fexpensive-optimizations \
                   -Wall -pedantic -Wno-long-long -fPIC
-  ARCHCXXFLAGS += $(ARCHCFLAGS)
-  ARCHLDFLAGS  += -Wl,-rpath,'$$ORIGIN/../lib'
-  ARCHLIBS     += -lopenblas -lz -lm
+  CXXFLAGS ?= -fexpensive-optimizations \
+  LDFLAGS  ?= -Wl,-rpath,'$$ORIGIN/../lib'
+  ARCHLIBS += -lopenblas -lz -lm
 endif # if Linux
 
 #####################################################################

config/default.mk

-include ${FSLCONFDIR}/common/buildSettings.mk
-include ${FSLCONFDIR}/common/vars.mk
-include ${FSLCONFDIR}/common/rules.mk
+# Platform specific settings and defaults,
+# which are used by vars.mk
+include ${FSLCONFDIR}/buildSettings.mk
+
+# Definition of variables controlling
+# compilation and installation
+include ${FSLCONFDIR}/vars.mk
+
+# Make rules
+include ${FSLCONFDIR}/rules.mk

config/common/vars.mk → config/vars.mk

 #########################################################
 # Variables used for FSL project compilation/installation
+#
+# Default compiler/platform specific variables are
+# initialised in buildSettings.mk, which is included
+# before this file. Project specific variables are
+# initialised in the project Makefile.
 #########################################################
 
 # All projects must specify a name
@@ -12,6 +17,7 @@ USRLDFLAGS      = # Project-specific linker flags
 USRINCFLAGS     = # Project-specific include directories
 USRCFLAGS       = # Project-specific compiler flags for C projects
 USRCXXFLAGS     = # Project-specific compiler flags for C++ projects
+USRCPPFLAGS     = # Project-specific preprocessor flags
 LIBS            = # Project-specific libraries to link against for C
                   # and C++ projects - these are incorporated into the
                   # final LDFLAGS, below.
@@ -66,29 +72,46 @@ INCFLAGS = ${USRINCFLAGS} -I. -I${DEVINCDIR} -I${INCDIR}
 # Final compiler/linker flags
 #############################
 
-# Ignore flags provided by the environment
-CFLAGS      =
-CXXFLAGS    =
-CPPFLAGS    =
-NVCCFLAGS   =
-LDFLAGS     =
-NVCCLDFLAGS =
+# Allow flags to be added by the environment
+CFLAGS      ?=
+CXXFLAGS    ?=
+CPPFLAGS    ?=
+NVCCFLAGS   ?=
+LDFLAGS     ?=
+NVCCLDFLAGS ?=
 
 # All projects must use these flags for
 # compilation/linking, using the form:
 #
-# $(CC)   $(CFLAGS)    <project flags/files> $(LDFLAGS)
-# $(CXX)  $(CXXFLAGS)  <project flags/files> $(LDFLAGS)
-# $(NVCC) $(NVCCFLAGS) <project flags/files> $(NVCCLDFLAGS)
+# $(CC)   $(CFLAGS)    <input/output files> $(LDFLAGS)
+# $(CXX)  $(CXXFLAGS)  <input/output files> $(LDFLAGS)
+# $(NVCC) $(NVCCFLAGS) <input/output files> $(NVCCLDFLAGS)
 #
 # LDFLAGS *must* come at the end, to ensure proper linking.
 
-LDFLAGS       += ${ARCHLDFLAGS} ${USRLDFLAGS} \
-                 -L. -L${DEVLIBDIR} -L${LIBDIR} \
-                  ${LIBS} ${ARCHLIBS}
-NVCCLDFLAGS   += ${ARCHNVCCLDFLAGS} ${USRNVCCLDFLAGS} \
-                 -L. -L${DEVLIBDIR} -L${LIBDIR} \
-                 ${CUDALIBS}
-CFLAGS        += ${ARCHCFLAGS}    ${USRCFLAGS}    ${INCFLAGS}
-CXXFLAGS      += ${ARCHCXXFLAGS}  ${USRCXXFLAGS}  ${INCFLAGS}
-NVCCFLAGS     += ${ARCHNVCCFLAGS} ${USRNVCCFLAGS} ${INCFLAGS}
+# The order in which the final FLAGS variables are
+# constructed here is important:
+#
+#  1. Flags provided by the environment come first
+#  2. ARCH* flags defined in buildSettings.mk come next
+#  3. USR* flags defined in the Project Makefile come
+#     last.
+#
+# Many compiler options, if specified multiple times,
+# are interpreted such that only the last option takes
+# effect. This essentiallyy means that, because of the
+# construction order, a project Makefile can override
+# the default options specified in buildSettings.mk,
+# which in turn can override options provided by the
+# environment.
+
+CPPFLAGS    += ${ARCHCPPFLAGS} ${USRCPPFLAGS}
+CFLAGS      += ${CPPFLAGS} ${ARCHCFLAGS}   ${USRCFLAGS}   ${INCFLAGS}
+CXXFLAGS    += ${CPPFLAGS} ${ARCHCXXFLAGS} ${USRCXXFLAGS} ${INCFLAGS}
+NVCCFLAGS   += ${ARCHNVCCFLAGS} ${USRNVCCFLAGS} ${INCFLAGS}
+LDFLAGS     += ${ARCHLDFLAGS} ${USRLDFLAGS} \
+               -L. -L${DEVLIBDIR} -L${LIBDIR} \
+                ${LIBS} ${ARCHLIBS}
+NVCCLDFLAGS += ${ARCHNVCCLDFLAGS} ${USRNVCCLDFLAGS} \
+               -L. -L${DEVLIBDIR} -L${LIBDIR} \
+               ${CUDALIBS}