support: Link links-dso-program-c against libgcc_s

If C++ support is not available, links-dso-program-c is used
instead of the C++ version.  The C version was not linked against
libgcc_s, which meant that thread cancellation and the backtrace
function did not work in containers tests in that situation.

Reviewed-by: Sam James <sam@gentoo.org>

2 files changed, 22 insertions, 0 deletions

diff --git a/support/Makefile b/support/Makefile
index 59a9974..0c67055 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -281,6 +281,8 @@ CFLAGS-temp_file.c += -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64
 
 ifeq (,$(CXX))
 LINKS_DSO_PROGRAM = links-dso-program-c
+CFLAGS-links-dso-program-c.c += -fexceptions
+LDLIBS-links-dso-program-c = -lgcc -lgcc_s $(libunwind)
 else
 LINKS_DSO_PROGRAM = links-dso-program
 LDLIBS-links-dso-program = -lstdc++ -lgcc -lgcc_s $(libunwind)
diff --git a/support/links-dso-program-c.c b/support/links-dso-program-c.c
index 5fcbab2..efe65b4 100644
--- a/support/links-dso-program-c.c
+++ b/support/links-dso-program-c.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <dlfcn.h>
 
 /* makedb needs selinux dso's.  */
 #ifdef HAVE_SELINUX
@@ -13,6 +14,20 @@
    such dependencies.
 */
 
+/* Use attribute cleanup to force linking against libgcc_s.  */
+static void
+cleanup_function (int *ignored)
+{
+  puts ("cleanup performed");
+}
+
+void
+invoke_callback (void (*callback) (int *))
+{
+  __attribute__ ((cleanup (cleanup_function))) int i = 0;
+  callback (&i);
+}
+
 int
 main (int argc, char **argv)
 {
@@ -22,5 +37,10 @@ main (int argc, char **argv)
   /* This exists to force libselinux.so to be required.  */
   printf ("selinux %d\n", is_selinux_enabled ());
 #endif
+  /* Prevent invoke_callback from being optimized away.  */
+  {
+    Dl_info dli;
+    dladdr (invoke_callback, &dli);
+  }
   return 0;
 }