scons: Add a convenience method to set RPATH for local libraries.
When linking in a dynamic library which is in the gem5 build directory,
it's useful to set RPATH so that you don't have to set LD_LIBRARY_PATH
when you run gem5 so that the dynamic linker can find it.
Since it's tricky and not entirely obvious how to set up those paths
correctly, this change adds a small convenience function which does
that for you. It also handles situations where the same dynamic
library may be linked into different binaries in different directories
which each need a different relative RPATH. It does that by letting the
environment for each binary set a construction variable which says
how to get from that particular binary back to the build directory.
This helper method then sets RPATH to start at $ORIGIN (the binary),
to follow that relative path to the variant build directory, and then
the per-library but not per-binary path to the library's directory.
This change also adds the -z origin linker flag which makes the linker
handle $ORIGIN properly.
Change-Id: I45f4d72cd14396a73e0b963cea6a39d9bfb7f984
Reviewed-on: https://gem5-review.googlesource.com/c/16566
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>
diff --git a/SConstruct b/SConstruct
index 5c8f649..026327c 100755
--- a/SConstruct
+++ b/SConstruct
@@ -1072,6 +1072,27 @@
main.Append(BUILDERS = { 'PartialShared' : partial_shared_builder,
'PartialStatic' : partial_static_builder })
+def add_local_rpath(env, *targets):
+ '''Set up an RPATH for a library which lives in the build directory.
+
+ The construction environment variable BIN_RPATH_PREFIX should be set to
+ the relative path of the build directory starting from the location of the
+ binary.'''
+ for target in targets:
+ target = env.Entry(target)
+ if not target.isdir():
+ target = target.dir
+ relpath = os.path.relpath(target.abspath, env['BUILDDIR'])
+ components = [
+ '\\$$ORIGIN',
+ '${BIN_RPATH_PREFIX}',
+ relpath
+ ]
+ env.Append(RPATH=[env.Literal(os.path.join(*components))])
+
+main.Append(LINKFLAGS=Split('-z origin'))
+main.AddMethod(add_local_rpath, 'AddLocalRPATH')
+
# builds in ext are shared across all configs in the build root.
ext_dir = abspath(joinpath(str(main.root), 'ext'))
ext_build_dirs = []
diff --git a/src/SConscript b/src/SConscript
index 81b6cd3..ef7e670 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -449,6 +449,10 @@
if objs is None:
objs = self.srcs_to_objs(env, self.sources)
+ env = env.Clone()
+ env['BIN_RPATH_PREFIX'] = os.path.relpath(
+ env['BUILDDIR'], self.path(env).dir.abspath)
+
if env['STRIP_EXES']:
stripped = self.path(env)
unstripped = env.File(str(stripped) + '.unstripped')
