toolchain: improve musl check to support static toolchains

The check_musl function currently builds a program and verifies if the
program interpreter starts with /lib/ld-musl. While this works fine
for dynamically linked programs, this obviously doesn't work for a
purely static musl toolchain such as [1].

There is no easy way to identify a toolchain as using the musl C
library. For glibc, dynamic linking is always supported, so we look at
the dynamic linker name. For uClibc, there is a distinctive
uClibc_config.h header file. There is no such distinctive feature in
musl.

We end up resorting to looking for the string MUSL_LOCPATH, which is
used by musl locale_map.c source file. This string has been present in
musl since 2014. It certainly isn't a very stable or convincing
solution to identify the C library as being musl, but it's the best we
could find.

Note that we are sure there is a libc.a file, because the
check_unusable_toolchain function checks that there is a such a file.

[1] http://autobuild.buildroot.net/toolchains/tarballs/br-arm-musl-static-2018.05.tar.bz2

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

diff --git a/toolchain/helpers.mk b/toolchain/helpers.mk
index 1792286add096097e7196f6ac7dc4229c5aa5212..e5520c00c321997436aca2105d586f0363095c9d 100644 (file)
--- a/toolchain/helpers.mk
+++ b/toolchain/helpers.mk
@@ -241,14 +241,11 @@ check_glibc = \
 # $2: cross-readelf path
 check_musl = \
        __CROSS_CC=$(strip $1) ; \
-       __CROSS_READELF=$(strip $2) ; \
-       echo 'void main(void) {}' | $${__CROSS_CC} -x c -o $(BUILD_DIR)/.br-toolchain-test.tmp - >/dev/null 2>&1; \
-       if ! $${__CROSS_READELF} -l $(BUILD_DIR)/.br-toolchain-test.tmp 2> /dev/null | grep 'program interpreter: /lib/ld-musl' -q; then \
-               rm -f $(BUILD_DIR)/.br-toolchain-test.tmp*; \
+       libc_a_path=`$${__CROSS_CC} -print-file-name=libc.a` ; \
+       if ! strings $${libc_a_path} | grep -q MUSL_LOCPATH ; then \
                echo "Incorrect selection of the C library" ; \
                exit -1; \
-       fi ; \
-       rm -f $(BUILD_DIR)/.br-toolchain-test.tmp*
+       fi
 
 #
 # Check the conformity of Buildroot configuration with regard to the

diff --git a/toolchain/toolchain-external/pkg-toolchain-external.mk b/toolchain/toolchain-external/pkg-toolchain-external.mk
index 8b2c283654531f47d65413964e91a5d581828545..02d992531da1c4ad4c298b246313efb7721947f4 100644 (file)
--- a/toolchain/toolchain-external/pkg-toolchain-external.mk
+++ b/toolchain/toolchain-external/pkg-toolchain-external.mk
@@ -557,8 +557,7 @@ define $(2)_CONFIGURE_CMDS
                $$(call check_uclibc,$$$${SYSROOT_DIR}) ; \
        elif test "$$(BR2_TOOLCHAIN_EXTERNAL_MUSL)" = "y" ; then \
                $$(call check_musl,\
-                       "$$(TOOLCHAIN_EXTERNAL_CC) $$(TOOLCHAIN_EXTERNAL_CFLAGS)",\
-                       $$(TOOLCHAIN_EXTERNAL_READELF)) ; \
+                       "$$(TOOLCHAIN_EXTERNAL_CC) $$(TOOLCHAIN_EXTERNAL_CFLAGS)") ; \
        else \
                $$(call check_glibc,$$$${SYSROOT_DIR}) ; \
        fi