test: build the crashing test binary outside of the test

So we don't have to pull in gcc and other stuff into it.

Also, make the test itself a bit more robust and debug-able.

src/test/meson.build

@@ -275,6 +275,17 @@ executables += [
                 'sources' : files('test-compress.c'),
                 'link_with' : [libshared],
         },
+        test_template + {
+                'sources' : files('test-coredump-stacktrace.c'),
+                'type' : 'manual',
+                # This test intentionally crashes with SIGSEGV by dereferencing a NULL pointer
+                # to generate a coredump with a predictable stack trace. To prevent sanitizers
+                # from catching the error first let's disable them explicitly, and also always
+                # build with minimal optimizations to make the stack trace predictable no matter
+                # what we build the rest of systemd with
+                'override_options' : ['b_sanitize=none', 'strip=false', 'debug=true'],
+                'c_args' : ['-fno-sanitize=all', '-fno-optimize-sibling-calls', '-O1'],
+        },
         test_template + {
                 'sources' : files('test-cryptolib.c'),
                 'dependencies' : libopenssl,

src/test/test-coredump-stacktrace.c

@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+/* This is a test program that intentionally segfaults so we can generate a
+ * predictable-ish stack trace in tests. */
+
+#include <stdlib.h>
+
+__attribute__((noinline))
+static void baz(int *x) {
+        *x = rand();
+}
+
+__attribute__((noinline))
+static void bar(void) {
+        int * volatile x = NULL;
+
+        baz(x);
+}
+
+__attribute__((noinline))
+static void foo(void) {
+        bar();
+}
+
+int main(void) {
+        foo();
+
+        return 0;
+}