fix atomicity and other issues installing dynamic linker symlink

ln -sf is non-atomic; it unlinks the destination first. instead, make
a temporary link and rename it into place.

this commit also fixes some of the dependency tracking behavior for
the link. depending on the directory it's to be installed in is not
reasonable; it causes a new link to be attempted if the library
directory has been modified, but does not attempt to make a new link
just because libc has been updated. instead, depend on the target to
be linked to. this will ensure that, if prefix has changed but
syslibdir has not, the link will be updated to point to the new
prefix.

diff --git a/Makefile b/Makefile
index 33c2de1b19a2f877ecebf461fc42442a26eb6398..7e634dadfcd01f9aa96b0f5662028b66d7529518 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -155,11 +155,9 @@ $(DESTDIR)$(includedir)/bits/%: arch/$(ARCH)/bits/%
 $(DESTDIR)$(includedir)/%: include/%
        install -D -m 644 $< $@
 
-$(DESTDIR)$(LDSO_PATHNAME): $(DESTDIR)$(syslibdir)
-       ln -sf $(libdir)/libc.so $@ || true
-
-$(DESTDIR)$(syslibdir):
-       install -d -m 755 $(DESTDIR)$(syslibdir)
+$(DESTDIR)$(LDSO_PATHNAME): $(DESTDIR)$(libdir)/libc.so
+       test -d $(DESTDIR)$(syslibdir) || install -d -m 755 $(DESTDIR)$(syslibdir) || true
+       { ln -sf $(libdir)/libc.so $@.tmp.$$$$ && mv -f $@.tmp.$$$$ $@ ; } || true
 
 install-libs: $(ALL_LIBS:lib/%=$(DESTDIR)$(libdir)/%) $(if $(SHARED_LIBS),$(DESTDIR)$(LDSO_PATHNAME),)