test(libc): keep intentional aborts away from the system crash handler

guest_host_standard_error and exception_runtime fork children that end in
SIGABRT on purpose. When kernel.core_pattern pipes cores to a handler, as
Ubuntu's apport and systemd-coredump do, the kernel starts it for every
dumpable crash even with RLIMIT_CORE at 0. apport takes about 1.1 s per
crash here, so guest_host_standard_error spent 2.3 s waiting and timed out
at its 10 s limit under parallel ctest load. Marking those children
non-dumpable on Linux skips the handler: 2.29 s to 0.01 s and
1.17 s to 0.01 s, with the same SIGABRT and message checks.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

core/libs/tests/ExceptionRuntime.cpp

@@ -14,6 +14,9 @@
 #include <pthread.h>
 #include <sys/wait.h>
 #include <unistd.h>
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
 #include <unwind.h>
 
 extern "C" unsigned __cxa_uncaught_exceptions_nid_postfix();
@@ -172,6 +175,9 @@ void CheckDefaultTerminateMessage() {
     if (child == 0) {
         close(channel[0]);
         dup2(channel[1], 2);
+#ifdef __linux__
+        assert(prctl(PR_SET_DUMPABLE, 0) == 0);
+#endif
         throw std::runtime_error(message);
     }
     close(channel[1]);

core/libs/tests/GuestHostStandardError.cpp

@@ -11,6 +11,9 @@
 #include <string>
 #include <sys/wait.h>
 #include <unistd.h>
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
 
 extern "C" {
 FileStream* APS5_VABI freopen_nid_postfix(const char*, const char*, FileStream*);
@@ -25,6 +28,12 @@ extern FileStream* __stderrp_nid_postfix;
 
 static void Require(bool value) { if (!value) std::abort(); }
 
+static void SkipCrashHandler() {
+#ifdef __linux__
+    Require(::prctl(PR_SET_DUMPABLE, 0) == 0);
+#endif
+}
+
 enum class Redirect { Duplicate, Reopen };
 
 struct Outcome {
@@ -56,7 +65,10 @@ static Outcome Run(Redirect redirect, const std::filesystem::path& probe, bool t
         ::close(host[1]);
         RedirectGuest(redirect, probe);
         std::fputs("host\n", stderr);
-        if (terminate) throw std::runtime_error("report kept");
+        if (terminate) {
+            SkipCrashHandler();
+            throw std::runtime_error("report kept");
+        }
         if (redirect == Redirect::Reopen && fflush_nid_postfix(__stderrp_nid_postfix) != 0) ::_exit(71);
         ::_exit(0);
     }