[Buildroot] [PATCH v10 4/4] toolchain-external: create symlink ARCH_LIB_DIR->lib

[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' (ABI=n32; likewise for
lib64-fp in case of ABI=n64)

More generally the correct symbolic link is from (usr/)${ARCH_LIB_DIR}->lib.
However, feedback from Arnout Vandecappelle is that there are packages that
do depend on the lib32/lib64 symlink, even if ARCH_LIB_DIR is different.
Hence, these links must be kept.

Fix the problem as follows:
- For internal toolchains: no change
- For external toolchains: create a symlink ARCH_LIB_DIR->lib if
  ARCH_LIB_DIR is different from lib/lib32/lib64.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: "Yann E. Morin" <yann.morin.1998@free.fr>
Cc: Romain Naour <romain.naour@gmail.com>
Cc: Peter Korsgaard <peter@korsgaard.com>

---
 toolchain/toolchain-external/toolchain-external.mk | 23 ++++++++++++++++++++++
 1 file changed, 23 insertions(+)

v10:
- simplify after realization that skeleton symlink creation can be kept
  (thanks Thomas Petazzoni for noticing this)
v9:
- remove redundant mkdir's (handled by skeleton) (Yann)
v8:
- use helper only for external toolchain and incorporate ARCH_LIB_DIR
  definition (Arnout)
- keep lib32/lib64->lib symlink anyway
v7: rebase
v6: rebase only
v5:
- move internal toolchain logic into gcc-initial.mk
- also silence the internal toolchain link steps with $(Q)
v4:
- merge both helpers into one
- remove the separate target for the internal toolchain and hook into
  gcc-initial
- re-add deleted comment about MIPS64/n32
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: in output/staging/usr/ there would still be more directories than I
think are really necessary. This behavior is not changed by this patch, it
was already present before.
For example, with the mentioned Octeon III toolchain, output/staging/usr/
contains:
    bin      bin32      bin32-fp      bin64-fp,
    lib      lib32      lib32-fp      lib64-fp
    libexec  libexec32  libexec32-fp  libexec64-fp
    sbin     sbin32     sbin32-fp     sbin64-fp

where bin/lib/libexec/sbin seem to be the 64-bit equivalents of
bin32/lib32/libexec32/sbin32.
This is related to the behavior of copy_toolchain_sysroot in
toolchain/helpers.mk. It already attempts to filter out the unnecessary lib*
directories, but does not care about any bin/sbin/libexec directories.
As this poses no known problem and is not impacted by this patch, I make no
attempt to change it.

diff --git a/toolchain/toolchain-external/toolchain-external.mk b/toolchain/toolchain-external/toolchain-external.mk
index ddefd01..10f1edc 100644
--- a/toolchain/toolchain-external/toolchain-external.mk
+++ b/toolchain/toolchain-external/toolchain-external.mk
@@ -517,6 +517,27 @@ endef
 TOOLCHAIN_EXTERNAL_POST_INSTALL_STAGING_HOOKS += TOOLCHAIN_EXTERNAL_MUSL_LD_LINK
 endif
 
+# Create a symlink from (usr/)$(ARCH_LIB_DIR) to lib.
+# Note: the skeleton package additionally creates lib32->lib or lib64->lib
+# (as appropriate)
+#
+# $1: destination directory (TARGET_DIR / STAGING_DIR)
+create_lib_symlinks = \
+       $(Q)DESTDIR="$(strip $1)" ; \
+       ARCH_LIB_DIR="$(call toolchain_find_libdir,$(TOOLCHAIN_EXTERNAL_CC) $(TOOLCHAIN_EXTERNAL_CFLAGS))" ; \
+       if [ "$${ARCH_LIB_DIR}" != "lib" -a "$${ARCH_LIB_DIR}" != "$(SKELETON_LIB_SYMLINK)" ]; then \
+               ln -snf lib "$${DESTDIR}/$${ARCH_LIB_DIR}" ; \
+               ln -snf lib "$${DESTDIR}/usr/$${ARCH_LIB_DIR}" ; \
+       fi
+
+define TOOLCHAIN_EXTERNAL_CREATE_STAGING_LIB_SYMLINK
+       $(call create_lib_symlinks,$(STAGING_DIR))
+endef
+
+define TOOLCHAIN_EXTERNAL_CREATE_TARGET_LIB_SYMLINK
+       $(call create_lib_symlinks,$(TARGET_DIR))
+endef
+
 # Integration of the toolchain into Buildroot: find the main sysroot
 # and the variant-specific sysroot, then copy the needed libraries to
 # the $(TARGET_DIR) and copy the whole sysroot (libraries and headers)
@@ -732,6 +753,7 @@ endef
 TOOLCHAIN_EXTERNAL_BUILD_CMDS = $(TOOLCHAIN_BUILD_WRAPPER)
 
 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)
@@ -741,6 +763,7 @@ 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)
-- 
2.4.10