[Buildroot] [PATCHv3 for next 2/2] toolchain: create symlink to 'lib' from ARCH_LIB_DIR iso fixed lib32/lib64

[Thomas De Schampheleire <patrickdepinguin@gmail.com>]

From: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>

Currently, following symbolic links are created in both target and
staging directories:
- lib(32|64) --> lib
- usr/lib(32|64) --> lib

The decision for lib32 or lib64 is based on the target architecture
configuration in buildroot (BR2_ARCH_IS_64).

In at least one case this is not correct: when building for a Cavium Octeon
III processor using the toolchain from the Cavium Networks SDK, and
specifying -march=octeon3 in BR2_TARGET_OPTIMIZATION, libraries are expected
in directory 'lib32-fp' rather than 'lib32' (likewise for lib64-fp).

More generally, for external toolchains, the correct symbolic link is
from (usr/)${ARCH_LIB_DIR} to lib. For internal toolchains, current
toolchains always use either lib32 or lib64.

Fix the problem as follows:
- create symlink creation helpers in toolchain/helpers.mk
- for external toolchains, call these helpers based on ARCH_LIB_DIR
- for internal toolchains, call these helpers based on the existing
  fixed lib32/lib64 logic, moved from Makefile
- to fix build order problems, add the correct dependency on
  $(BUILD_DIR) from $(BUILD_DIR)/.root

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>

---
v3:
- update commit message wrapping
- change dependency on $(BUILD_DIR) to a order-only dependency
v2:
- fix 'lib32-fp' leftover in toolchain-buildroot
- silence commands creating symlink with $(Q)
- fix case where ARCH_LIB_DIR is 'lib'

Note: the handling in the internal toolchain is a bit awkward because it
explicitly adds a new target, but I don't see a much better way: it must
be done _before_ the toolchain is being built. The entire logic cannot
be done in Makefile as ARCH_LIB_DIR is not available there.
---
 Makefile                                             | 14 +-------------
 toolchain/helpers.mk                                 | 16 ++++++++++++++++
 toolchain/toolchain-buildroot/toolchain-buildroot.mk | 11 +++++++++++
 toolchain/toolchain-external/toolchain-external.mk   | 12 ++++++++++++
 4 files changed, 40 insertions(+), 13 deletions(-)

diff --git a/Makefile b/Makefile
index 338c992..de202b0 100644
--- a/Makefile
+++ b/Makefile
@@ -449,20 +449,10 @@ world: target-post-image
 $(BUILD_DIR) $(HOST_DIR) $(BINARIES_DIR) $(LEGAL_INFO_DIR) $(REDIST_SOURCES_DIR_TARGET) $(REDIST_SOURCES_DIR_HOST):
 	@mkdir -p $@
 
-# We make a symlink lib32->lib or lib64->lib as appropriate
-# MIPS64/n32 requires lib32 even though it's a 64-bit arch.
-ifeq ($(BR2_ARCH_IS_64)$(BR2_MIPS_NABI32),y)
-LIB_SYMLINK = lib64
-else
-LIB_SYMLINK = lib32
-endif
-
 $(STAGING_DIR):
 	@mkdir -p $(STAGING_DIR)/bin
 	@mkdir -p $(STAGING_DIR)/lib
-	@ln -snf lib $(STAGING_DIR)/$(LIB_SYMLINK)
 	@mkdir -p $(STAGING_DIR)/usr/lib
-	@ln -snf lib $(STAGING_DIR)/usr/$(LIB_SYMLINK)
 	@mkdir -p $(STAGING_DIR)/usr/include
 	@mkdir -p $(STAGING_DIR)/usr/bin
 	@ln -snf $(STAGING_DIR) $(BASE_DIR)/staging
@@ -475,15 +465,13 @@ RSYNC_VCS_EXCLUSIONS = \
 	--exclude .svn --exclude .git --exclude .hg --exclude .bzr \
 	--exclude CVS
 
-$(BUILD_DIR)/.root:
+$(BUILD_DIR)/.root: | $(BUILD_DIR)
 	mkdir -p $(TARGET_DIR)
 	rsync -a --ignore-times $(RSYNC_VCS_EXCLUSIONS) \
 		--chmod=Du+w --exclude .empty --exclude '*~' \
 		$(TARGET_SKELETON)/ $(TARGET_DIR)/
 	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt $(TARGET_DIR_WARNING_FILE)
-	@ln -snf lib $(TARGET_DIR)/$(LIB_SYMLINK)
 	@mkdir -p $(TARGET_DIR)/usr
-	@ln -snf lib $(TARGET_DIR)/usr/$(LIB_SYMLINK)
 	touch $@
 
 $(TARGET_DIR): $(BUILD_DIR)/.root
diff --git a/toolchain/helpers.mk b/toolchain/helpers.mk
index 3121da4..b4879e0 100644
--- a/toolchain/helpers.mk
+++ b/toolchain/helpers.mk
@@ -1,5 +1,21 @@
 # This Makefile fragment declares toolchain related helper functions.
 
+# Create the necessary symlink from (usr/)lib32|lib64|lib32-fp|... to lib
+# In general, for external toolchains, the correct link name is $ARCH_LIB_DIR.
+create_staging_lib_symlink = \
+	LIB_SYMLINK="$(strip $1)" ; \
+	if [ "$${LIB_SYMLINK}" != "lib" ]; then \
+		ln -snf lib $(STAGING_DIR)/$${LIB_SYMLINK} ; \
+		ln -snf lib $(STAGING_DIR)/usr/$${LIB_SYMLINK} ; \
+	fi
+
+create_target_lib_symlink = \
+	LIB_SYMLINK="$(strip $1)" ; \
+	if [ "$${LIB_SYMLINK}" != "lib" ]; then \
+	    ln -snf lib $(TARGET_DIR)/$${LIB_SYMLINK} ; \
+	    ln -snf lib $(TARGET_DIR)/usr/$${LIB_SYMLINK} ; \
+	fi
+
 # The copy_toolchain_lib_root function copies a toolchain library and
 # its symbolic links from the sysroot directory to the target
 # directory. Note that this function is used both by the external
diff --git a/toolchain/toolchain-buildroot/toolchain-buildroot.mk b/toolchain/toolchain-buildroot/toolchain-buildroot.mk
index b30cc33..3ccb030 100644
--- a/toolchain/toolchain-buildroot/toolchain-buildroot.mk
+++ b/toolchain/toolchain-buildroot/toolchain-buildroot.mk
@@ -12,6 +12,17 @@ BR_LIBC = $(call qstrip,$(BR2_TOOLCHAIN_BUILDROOT_LIBC))
 
 TOOLCHAIN_BUILDROOT_DEPENDENCIES = host-gcc-final
 
+ifeq ($(BR2_ARCH_IS_64)$(BR2_MIPS_NABI32),y)
+LIB_SYMLINK = lib64
+else
+LIB_SYMLINK = lib32
+endif
+
+host-gcc-final: create-lib-symlinks
+create-lib-symlinks: $(STAGING_DIR) $(TARGET_DIR)
+	$(call create_staging_lib_symlink,$(LIB_SYMLINK))
+	$(call create_target_lib_symlink,$(LIB_SYMLINK))
+
 TOOLCHAIN_BUILDROOT_ADD_TOOLCHAIN_DEPENDENCY = NO
 
 $(eval $(virtual-package))
diff --git a/toolchain/toolchain-external/toolchain-external.mk b/toolchain/toolchain-external/toolchain-external.mk
index e05957c..16e398c 100644
--- a/toolchain/toolchain-external/toolchain-external.mk
+++ b/toolchain/toolchain-external/toolchain-external.mk
@@ -600,6 +600,16 @@ define TOOLCHAIN_EXTERNAL_INSTALL_SYSROOT_LIBS
 	$(call copy_toolchain_sysroot,$${SYSROOT_DIR},$${ARCH_SYSROOT_DIR},$${ARCH_SUBDIR},$${ARCH_LIB_DIR},$${SUPPORT_LIB_DIR})
 endef
 
+define TOOLCHAIN_EXTERNAL_CREATE_STAGING_LIB_SYMLINK
+	$(Q)ARCH_LIB_DIR="$(call toolchain_find_libdir,$(TOOLCHAIN_EXTERNAL_CC) $(TOOLCHAIN_EXTERNAL_CFLAGS))" ; \
+	$(call create_staging_lib_symlink,$${ARCH_LIB_DIR})
+endef
+
+define TOOLCHAIN_EXTERNAL_CREATE_TARGET_LIB_SYMLINK
+	$(Q)ARCH_LIB_DIR="$(call toolchain_find_libdir,$(TOOLCHAIN_EXTERNAL_CC) $(TOOLCHAIN_EXTERNAL_CFLAGS))" ; \
+	$(call create_target_lib_symlink,$${ARCH_LIB_DIR})
+endef
+
 # Special installation target used on the Blackfin architecture when
 # FDPIC is not the primary binary format being used, but the user has
 # nonetheless requested the installation of the FDPIC libraries to the
@@ -699,6 +709,7 @@ define TOOLCHAIN_EXTERNAL_INSTALL_GDBINIT
 endef
 
 define TOOLCHAIN_EXTERNAL_INSTALL_STAGING_CMDS
+	$(TOOLCHAIN_EXTERNAL_CREATE_STAGING_LIB_SYMLINK)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_SYSROOT_LIBS)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_WRAPPER)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_GDBINIT)
@@ -708,6 +719,7 @@ endef
 # and the target directory, we do everything within the
 # install-staging step, arbitrarily.
 define TOOLCHAIN_EXTERNAL_INSTALL_TARGET_CMDS
+	$(TOOLCHAIN_EXTERNAL_CREATE_TARGET_LIB_SYMLINK)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_TARGET_LIBS)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_BFIN_FDPIC)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_BFIN_FLAT)
-- 
1.8.5.1