Only using clang in macOS systems that also have GCC

Until now, when Maneage was built on a macOS that had both a clang and GCC,
we would make links to both. But this cause many conflicts in some
high-level programs (for example Numpy and etc, all the programs where we
have explicity set 'export CC=clang' before the build recipe). This happens
because the GCC that is built on a macOS isn't complete for some
operations.

To fix this problem, when we are on a macOS, we explicity set 'gcc' to
point to 'clang' and 'g++' to point to 'clang++'. We also don't link to the
host's C-preprocessor ('cpp') on macOS systems because this is only a GNU
feature and using the GNU CPP is also known to have some basic
problems. For example this was reported by Mahdieh Nabavi (which was the
main trigger for this work):

  ld: Symbol not found: ___keymgr_global
    Referenced from: /Users/Mahdieh/build/software/installed/bin/cpp
    Expected in: /usr/lib/libSystem.B.dylib

Also, to avoid linking to another link on the host tools (in the 'makelink'
function of 'basic.mk'), we are now using 'realpath'.

1 files changed, 58 insertions, 27 deletions

diff --git a/reproduce/software/make/basic.mk b/reproduce/software/make/basic.mk
index 2c7401e..b9678d0 100644
--- a/reproduce/software/make/basic.mk
+++ b/reproduce/software/make/basic.mk
@@ -152,6 +152,12 @@ backupservers = $(filter-out $(topbackupserver),$(backupservers_all))
 #
 # The double quotations after the starting 'export PATH' are necessary in
 # case the user's PATH has space-characters in it.
+#
+# We use 'realpath' here (part of GNU Coreutils which is already installed
+# by the time we use 'makelink') to avoid linking to a link (on the
+# host). 'realpath' will follow a link (and possibly other links in the
+# middle) to an actual file and return its address. When the location isn't
+# a link, it will just return it.
 syspath := $(PATH)
 makelink = origpath="$$PATH"; \
 	export PATH="$$(echo $(syspath) \
@@ -160,9 +166,9 @@ makelink = origpath="$$PATH"; \
 	                     | tr '\n' :)"; \
 	if type $(1) > /dev/null 2> /dev/null; then \
 	  if [ x$(3) = x ]; then \
-	    ln -sf "$$(which $(1))" $(ibdir)/$(1); \
+	    ln -sf "$$(realpath $$(which $(1)))" $(ibdir)/$(1); \
 	  else \
-	    ln -sf "$$(which $(1))" $(ibdir)/$(3); \
+	    ln -sf "$$(realpath $$(which $(1)))" $(ibdir)/$(3); \
 	  fi; \
 	else \
 	  if [ "x$(strip $(2))" = xmandatory ]; then \
@@ -177,11 +183,6 @@ $(ibdir) $(ildir):; mkdir $@
 $(ibidir)/low-level-links: $(ibidir)/grep-$(grep-version) \
                            | $(ibdir) $(ildir)
 
-        # Not-installed (but necessary in some cases) compilers.
-        #  Clang is necessary for CMake.
-	$(call makelink,clang)
-	$(call makelink,clang++)
-
         # Mac OS specific
 	$(call makelink,mig)
 	$(call makelink,xcrun)
@@ -1278,6 +1279,16 @@ $(ibidir)/gcc-$(gcc-version): $(ibidir)/binutils-$(binutils-version)
 	tarball=gcc-$(gcc-version).tar.xz
 	$(call import-source, $(gcc-url), $(gcc-checksum))
 
+        # To avoid any previous build in '.local/bin' causing problems in
+        # this build/links of this GCC, we'll first delete all the possibly
+        # built/existing compilers in this project. Note that GCC also
+        # installs several executables like this 'x86_64-pc-linux-gnu-gcc',
+        # 'x86_64-pc-linux-gnu-gcc-ar' or 'x86_64-pc-linux-gnu-g++'.
+	rm -rf $(ildir)/gcc $(ildir)/libcc* $(ildir)/libgcc*
+	rm -f $(ibdir)/*gcc* $(ibdir)/gcov* $(ibdir)/cc $(ibdir)/c++
+	rm -f $(ibdir)/*g++ $(ibdir)/cpp $(ibdir)/gfortran $(ibdir)/strip
+	rm -rf $(ildir)/libgfortran* $(ildir)/libstdc* rm $(idir)/x86_64*
+
         # GCC builds is own libraries in '$(idir)/lib64'. But all other
         # libraries are in '$(idir)/lib'. Since this project is only for a
         # single architecture, we can trick GCC into building its libraries
@@ -1285,34 +1296,53 @@ $(ibidir)/gcc-$(gcc-version): $(ibidir)/binutils-$(binutils-version)
         # link to '$(idir)/lib'.
 	if [ $(host_cc) = 1 ]; then
 
-          # Make sure we don't have any of the program we want to link to
-          # in the '.local/bin' directory.
-	  rm -f $(ibdir)/cc
-	  rm -f $(ibdir)/c++
-	  rm -f $(ibdir)/gcc
-	  rm -f $(ibdir)/cpp
-	  rm -f $(ibdir)/strip;
-	  rm -f $(ibdir)/gfortran;
-
-          # Put links to the host's tools in '.local/bin'.
-	  $(call makelink,cc)
-	  $(call makelink,cpp)
-	  $(call makelink,cc,,gcc)
+          # Put links to the host's tools in '.local/bin'. Note that some
+          # macOS systems have both a native clang *and* a GNU C Compiler
+          # (note that this is different from the "normal" macOS situation
+          # where 'gcc' actually points to clang, here we mean when 'gcc'
+          # is actually the GNU C Compiler).
+          #
+          # In such cases, the GCC isn't complete and using it will cause
+          # problems when building high-level tools (for example openBLAS,
+          # rpcsvc-proto, CMake, xlsxio, Python or Matplotlib among
+          # others). To avoid such situations macOSs are configured like
+          # this: we'll simply set 'gcc' to point to 'clang' and won't set
+          # 'gcc' to point to the system's 'gcc'.
+          #
+          # Also, note that LLVM's clang doesn't have a C Pre-Processor. So
+          # we will only put a link to the host's 'cpp' if the system is
+          # not macOS. On macOS systems that have a real GCC installed,
+          # having GNU CPP in the project build directory is known to cause
+          # problems with 'libX11'.
 	  $(call makelink,gfortran)
-	  $(call makelink,c++,,g++)
 	  $(call makelink,strip,mandatory)
+	  if [ x$(on_mac_os) = xyes ]; then
+	    $(call makelink,clang)
+	    $(call makelink,clang++)
+	    $(call makelink,clang,,gcc)
+	    $(call makelink,clang++,,g++)
+	  else
+	    $(call makelink,cpp)
+	    $(call makelink,gcc)
+	    $(call makelink,g++)
+	  fi
+
+          # We also want to have the two 'cc' and 'c++' in the build
+          # directory that point to the selected compiler. With the checks
+          # above, 'gcc' and 'g++' will point to the proper compiler, so
+          # we'll use them to define 'cc' and 'c++'.
+	  $(call makelink,gcc,,cc)
+	  $(call makelink,g++,,c++)
+
+          # Get the first line of the compiler's '--version' output and put
+          # that into the target (so we know want compiler was used).
 	  ccinfo=$$(gcc --version | awk 'NR==1')
 	  echo "C compiler (""$$ccinfo"")" > $@
 
 	else
 
-          # We are building GCC, so to avoid any previous build in
-          # '.local/bin', we'll delete all the files that GCC builds from
-          # there.
+          # Mark the current directory.
 	  current_dir=$$(pwd)
-	  rm -f $(ibdir)/gcc* $(ibdir)/g++ $(ibdir)/gfortran $(ibdir)/gcov*
-	  rm -rf $(ildir)/gcc $(ildir)/libcc* $(ildir)/libgcc*
-	  rm -rf $(ildir)/libgfortran* $(ildir)/libstdc* rm $(idir)/x86_64*
 
           # We don't want '.local/lib' and '.local/lib64' to be separate.
 	  ln -fs $(ildir) $(idir)/lib64
@@ -1406,6 +1436,7 @@ $(ibidir)/gcc-$(gcc-version): $(ibidir)/binutils-$(binutils-version)
 
           # Set 'cc' to point to 'gcc'.
 	  ln -sf $(ibdir)/gcc $(ibdir)/cc
+	  ln -sf $(ibdir)/g++ $(ibdir)/c++
 
           # Write the final target.
 	  echo "GNU Compiler Collection (GCC) $(gcc-version)" > $@