testsuite: require libc sym for -shared

Targets whose binutils support -shared, but that don't have a shared
libc, and that can't add PDC (non-PIC) to shared libraries, may
succeed at the effective target test for -shared, because it brings
nothing from libc, but tests that rely on -shared and that use bits
from libc, such as g++.dg/lto/pr108772, fail despite requiring the
shared effective target.

Extend the effective target test to bring malloc() from libc, that's
likely to be present in libc and bring a substantial amount of code if
no shared libc is available.


for  gcc/testsuite/ChangeLog

	* lib/target-supports.exp (check_effective_target_shared):
	Check for a static-only libc.

1 files changed, 8 insertions, 2 deletions

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 994e83f..8ee082f 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -1391,10 +1391,16 @@ proc check_effective_target_aarch64_tlsle32 { } {
 proc check_effective_target_shared { } {
     # 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.
+    # requires GOT references, and with a libc symbol that would
+    # bring in significant parts of a static-only libc.  Absent a
+    # shared libc, this would make -shared tests fail, so we don't
+    # want to enable the shared effective target then.
     return [check_no_compiler_messages shared executable {
+	#include <stdlib.h>
 	extern int foo (void); extern int bar;
-	int baz (void) { return foo () + bar; }
+	char *baz (void) {
+	    return foo () + (char*) malloc (bar);
+	}
     } "-shared -fpic"]
 }