[gcc r14-8506] testsuite: require libc sym for -shared

[Alexandre Oliva]

https://gcc.gnu.org/g:4bdcc8b3bf239c48140647c19d3addebc5d4b930

commit r14-8506-g4bdcc8b3bf239c48140647c19d3addebc5d4b930
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Mon Jan 29 15:08:35 2024 -0300

    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.

Diff:
---
 gcc/testsuite/lib/target-supports.exp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 994e83fc9e95..8ee082f21f98 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"]
 }