testsuite, Darwin: Allow for undefined symbols in shared test.

Darwin's linker defaults to error on undefined (which makes it look as
if we do not support shared, leading to tests being marked incorrectly
as unsupported).

This fixes the issue by allowing the symbols used in the target
supports test to be undefined.

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp (check_effective_target_shared):
	Allow the external symbols referenced in the test to be undefined.

1 files changed, 8 insertions, 1 deletions

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 8aefb32..f66dcaa 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -1385,6 +1385,13 @@ proc check_effective_target_aarch64_tlsle32 { } {
 # emitted, 0 otherwise.
 
 proc check_effective_target_shared { } {
+    # Darwin's linker defaults to error on undefined (which makes it look as
+    # if we do not support shared) but we can tell it to allow the symbols used
+    # here to be undefined.
+    set extra_flags ""
+    if { [istarget *-*-darwin\[912\]*] } {
+      set extra_flags "-Wl,-U,_foo,-U,_bar"
+    }
     # Note that M68K has a multilib that supports -fpic but not
     # -fPIC, so we need to check both.  We test with a program that
     # requires GOT references, and with a libc symbol that would
@@ -1397,7 +1404,7 @@ proc check_effective_target_shared { } {
 	char *baz (void) {
 	    return foo () + (char*) malloc (bar);
 	}
-    } "-shared -fpic"]
+    } "-shared -fpic $extra_flags"]
 }
 
 # Return 1 if -pie, -fpie and -fPIE are supported, 0 otherwise.