[cmake][make] Move -isystem flag at one place passing it to all compiler calls.

Moving from one header file per module to one module (and submodules) introduces
a few new restrictions. For instance, the module is built if any ot its headers
is included. This means that it will build the TGLIncludes.h-related modules
which in turn requires adjusting the -isystem path on OSX, allowing glew.h
to hooked before #include-ing system's gl.h (building system's OpenGL module).

Makefile

@@ -601,10 +601,23 @@ CXXMODULES_MODULEMAP_CONTENTS :=
 ALLHDRS  := include/module.modulemap
 ROOT_CXXMODULES_CXXFLAGS =  -fmodules -fcxx-modules -fmodules-cache-path=$(ROOT_OBJDIR)/include/pcms/
 ROOT_CXXMODULES_CFLAGS =  -fmodules -fmodules-cache-path=$(ROOT_OBJDIR)/include/pcms/
+
 # FIXME: OSX doesn't support -fmodules-local-submodule-visibility because its
 # Frameworks' modulemaps predate the flag.
 ifneq ($(PLATFORM),macosx)
 ROOT_CXXMODULES_CXXFLAGS += -Xclang -fmodules-local-submodule-visibility
+else
+# FIXME: TGLIncludes and alike depend on glew.h doing special preprocessor
+# trickery to override the contents of system's OpenGL.
+# On OSX #include TGLIncludes.h will trigger the creation of the system
+# OpenGL.pcm. Once it is built, glew cannot use preprocessor trickery to 'fix'
+# the translation units which it needs to 'rewrite'. The translation units
+# which need glew support are in graf3d. However, depending on the modulemap
+# organization we could request it implicitly (eg. one big module for ROOT).
+# In these cases we need to 'prepend' this include path to the compiler in order
+# for glew.h to it its trick.
+ROOT_CXXMODULES_CXXFLAGS +=  -isystem $(ROOT_SRCDIR)/graf3d/glew/isystem/
+ROOT_CXXMODULES_CFLAGS +=  -isystem $(ROOT_SRCDIR)/graf3d/glew/isystem/
 endif # not macos
 
 CXXFLAGS += $(ROOT_CXXMODULES_CXXFLAGS)

cmake/modules/CheckCompiler.cmake

@@ -130,7 +130,19 @@ if(cxxmodules)
     file(COPY ${CMAKE_SOURCE_DIR}/build/unix/module.modulemap DESTINATION ${ROOT_INCLUDE_DIR})
     # This var is useful when we want to compile things without cxxmodules.
     set(ROOT_CXXMODULES_CXXFLAGS "-fmodules -fcxx-modules -fmodules-cache-path=${CMAKE_BINARY_DIR}/include/pcms/")
-    if(NOT APPLE)
+    if(APPLE)
+     # FIXME: TGLIncludes and alike depend on glew.h doing special preprocessor
+     # trickery to override the contents of system's OpenGL.
+     # On OSX #include TGLIncludes.h will trigger the creation of the system
+     # OpenGL.pcm. Once it is built, glew cannot use preprocessor trickery to 'fix'
+     # the translation units which it needs to 'rewrite'. The translation units
+     # which need glew support are in graf3d. However, depending on the modulemap
+     # organization we could request it implicitly (eg. one big module for ROOT).
+     # In these cases we need to 'prepend' this include path to the compiler in order
+     # for glew.h to it its trick.
+      set(ROOT_CXXMODULES_CXXFLAGS "${ROOT_CXXMODULES_CFLAGS} -isystem ${CMAKE_SOURCE_DIR}/graf3d/glew/isystem ")
+      set(ROOT_CXXMODULES_CXXFLAGS "${ROOT_CXXMODULES_CXXFLAGS}  -isystem ${CMAKE_SOURCE_DIR}/graf3d/glew/isystem ")
+    else()
       set(ROOT_CXXMODULES_CXXFLAGS "${ROOT_CXXMODULES_CXXFLAGS} -Xclang -fmodules-local-submodule-visibility")
     endif(NOT APPLE)
     set(ROOT_CXXMODULES_CFLAGS "-fmodules -fmodules-cache-path=${CMAKE_BINARY_DIR}/include/pcms/")

graf3d/eve/CMakeLists.txt

@@ -23,10 +23,6 @@ if(MACOSX_GLU_DEPRECATED)
   add_definitions(-Wno-deprecated-declarations)
 endif()
 
-# We need to disallow the direct use of gl.h. This way people will see the error
-# and the suggested fix. This happens by providing our own "fake" system gl.h.
-set(CMAKE_CXX_FLAGS " -isystem ${CMAKE_CURRENT_SOURCE_DIR}/../glew/isystem ${CMAKE_CXX_FLAGS}")
-
 ROOT_GENERATE_DICTIONARY(G__Eve ${headers1} ${headers2} MODULE Eve LINKDEF LinkDef.h)
 
 ROOT_LINKER_LIBRARY(Eve *.cxx G__Eve.cxx LIBRARIES ${OPENGL_LIBRARIES} GLEW ${FTGL_LIBRARIES} Core DEPENDENCIES Geom Ged RGL Physics EG)

graf3d/eve/Module.mk

@@ -106,10 +106,7 @@ distclean::     distclean-$(MODNAME)
 ifeq ($(ARCH),win32)
 $(EVEO) $(EVEDO): CXXFLAGS += $(OPENGLINCDIR:%=-I%) $(FTGLINCDIR:%=-I%) $(FTGLCPPFLAGS)
 else
-# We need to disallow the direct use of gl.h. This way people will see the error
-# and the suggested fix. This happens by providing our own "fake" system gl.h.
-$(EVEO) $(EVEDO): CXXFLAGS += -isystem $(ROOT_SRCDIR)/graf3d/glew/isystem/ \
-		  $(OPENGLINCDIR:%=-I%) $(FTGLINCDIR:%=-I%) $(FTGLCPPFLAGS)
+$(EVEO) $(EVEDO): CXXFLAGS += $(OPENGLINCDIR:%=-I%) $(FTGLINCDIR:%=-I%) $(FTGLCPPFLAGS)
 $(EVEO): CXXFLAGS += $(GLEWINCDIR:%=-I%) $(GLEWCPPFLAGS)
 endif
 ifeq ($(MACOSX_GLU_DEPRECATED),yes)

graf3d/gl/CMakeLists.txt

@@ -34,10 +34,6 @@ if(MACOSX_GLU_DEPRECATED)
   add_definitions(-Wno-deprecated-declarations)
 endif()
 
-# We need to disallow the direct use of gl.h. This way people will see the error
-# and the suggested fix. This happens by providing our own "fake" system gl.h.
-set(CMAKE_CXX_FLAGS " -isystem ${CMAKE_CURRENT_SOURCE_DIR}/../glew/isystem ${CMAKE_CXX_FLAGS}")
-
 set_source_files_properties(src/TGLFontManager.cxx PROPERTIES COMPILE_FLAGS "${FTGL_CFLAGS}")
 set_source_files_properties(src/TGLText.cxx PROPERTIES COMPILE_FLAGS "${FTGL_CFLAGS}")
 

graf3d/gl/Module.mk

@@ -128,9 +128,7 @@ $(GLO) $(GLDO): CXXFLAGS += $(OPENGLINCDIR:%=-I%) -I$(WIN32GDKDIR)/gdk/src \
 $(GLDS):        CINTFLAGS += $(OPENGLINCDIR:%=-I%) -I$(WIN32GDKDIR)/gdk/src \
                              $(GDKDIRI:%=-I%) $(GLIBDIRI:%=-I%) $(GL2PSFLAGS)
 else
-# We need to disallow the direct use of gl.h. This way people will see the error
-# and the suggested fix. This happens by providing our own "fake" system gl.h.
-$(GLO) $(GLDO): CXXFLAGS += -isystem $(ROOT_SRCDIR)/graf3d/glew/isystem/ $(OPENGLINCDIR:%=-I%) $(GL2PSFLAGS)
+$(GLO) $(GLDO): CXXFLAGS += $(OPENGLINCDIR:%=-I%) $(GL2PSFLAGS)
 $(GLDS):        CINTFLAGS += $(OPENGLINCDIR:%=-I%) $(GL2PSFLAGS)
 endif
 

graf3d/gl/src/TGLOutput.cxx

@@ -16,10 +16,6 @@
 #include "TVirtualPS.h"
 #include "TGLViewer.h"
 #include "TSystem.h" // For gSystem
-// FIXME: Some gl2ps.h versions (see ROOT-8219) rely on including gl.h, which
-// in we shadow in our isystem/gl.h intentionally. Including TGLIncludes.h, will
-// temporary workaround the issue.
-#include "TGLIncludes.h"
 #include "gl2ps.h"
 #include "TError.h"
 #include <assert.h>

graf3d/glew/CMakeLists.txt

@@ -4,8 +4,5 @@
 
 include_directories(${OPENGL_INCLUDE_DIR})
 
-# We need to disallow the direct use of gl.h. This way people will see the error
-# and the suggested fix. This happens by providing our own "fake" system gl.h.
-set(CMAKE_C_FLAGS " -isystem ${CMAKE_CURRENT_SOURCE_DIR}/isystem ${GLEW_C_FLAGS}")
 ROOT_LINKER_LIBRARY(GLEW *.c LIBRARIES ${OPENGL_LIBRARIES})
 ROOT_INSTALL_HEADERS()

graf3d/glew/Module.mk

@@ -67,6 +67,4 @@ distclean-$(MODNAME): clean-$(MODNAME)
 distclean::     distclean-$(MODNAME)
 
 ##### extra rules ######
-# We need to disallow the direct use of gl.h. This way people will see the error
-# and the suggested fix. This happens by providing our own "fake" system gl.h
-$(GLEWO): CFLAGS += -isystem $(GLEWDIR)/isystem $(OPENGLINCDIR:%=-I%)
+$(GLEWO): CFLAGS += $(OPENGLINCDIR:%=-I%)