The gthr weak reference based single thread detection is unsafe with
static linking and in case of dynamic linking it's ineffective on musl
since pthread symbols are defined in libc.so.
Ideally this should be fixed for all targets, since glibc plans to move
libpthread.so into libc.so too and users want to static link to pthread
without --whole-archive: PR87189.
For now we have to explicitly opt out from the broken behaviour in the
config machinery of each target lib and libgcc was previously missed.
libgcc/ChangeLog:
2019-11-15 Szabolcs Nagy <szabolcs.n...@arm.com>
* config.host: Add t-gthr-noweak on *-*-musl*.
* config/t-gthr-noweak: New file.
diff --git a/libgcc/config.host b/libgcc/config.host
index 122113fc519..fe1b9ab93d5 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -1500,3 +1500,10 @@ aarch64*-*-*)
tm_file="${tm_file} aarch64/value-unwind.h"
;;
esac
+
+case ${host} in
+*-*-musl*)
+ # The gthr weak references are unsafe with static linking
+ tmake_file="$tmake_file t-gthr-noweak"
+ ;;
+esac
diff --git a/libgcc/config/t-gthr-noweak b/libgcc/config/t-gthr-noweak
new file mode 100644
index 00000000000..45a21e9361d
--- /dev/null
+++ b/libgcc/config/t-gthr-noweak
@@ -0,0 +1,2 @@
+# Don't use weak references for single-thread detection
+HOST_LIBGCC2_CFLAGS += -DGTHREAD_USE_WEAK=0
