[PATCH libevdev] test: detect if we're running inside gdb and disable forking

[Peter Hutterer]

The Check test framework forks by default which is annoying when running gdb.
Try to detect whether we're inside gdb by ptracing ourselves. If that works,
we're not inside a debugger. If it doesn't, then assume we're inside a
debugger and set CK_FORK to "no".

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 libevdev/libevdev.h |  5 +++--
 test/test-main.c    | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/libevdev/libevdev.h b/libevdev/libevdev.h
index c11c845..c5d12a4 100644
--- a/libevdev/libevdev.h
+++ b/libevdev/libevdev.h
@@ -177,8 +177,9 @@ extern "C" {
  *     git grep "suite_create"
  *     git grep "tcase_create"
  *
- * By default, check forks, making debugging harder. Run gdb as below to avoid
- * forking.
+ * By default, Check forks, making debugging harder. The test suite tries to detect
+ * if it is running inside gdb and disable forking. If that doesn't work for
+ * some reason, run gdb as below to avoid forking.
  *
  *     sudo CK_FORK=no CK_RUN_TEST="test case name" gdb ./test/test-libevdev
  *
diff --git a/test/test-main.c b/test/test-main.c
index 73d79c9..91128c3 100644
--- a/test/test-main.c
+++ b/test/test-main.c
@@ -22,6 +22,10 @@
 
 #include <config.h>
 #include <check.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
 
 extern Suite *event_name_suite(void);
 extern Suite *event_code_suite(void);
@@ -31,9 +35,42 @@ extern Suite *libevdev_has_event_test(void);
 extern Suite *libevdev_events(void);
 extern Suite *uinput_suite(void);
 
+static int
+is_debugger_attached(void)
+{
+	int status;
+	int rc;
+	int pid = fork();
+
+	if (pid == -1)
+		return 0;
+
+	if (pid == 0) {
+		int ppid = getppid();
+		if (ptrace(PTRACE_ATTACH, ppid, NULL, NULL) == 0) {
+			waitpid(ppid, NULL, 0);
+			ptrace(PTRACE_CONT, NULL, NULL);
+			ptrace(PTRACE_DETACH, ppid, NULL, NULL);
+			rc = 0;
+		} else
+			rc = 1;
+		_exit(rc);
+	} else {
+		waitpid(pid, &status, 0);
+		rc = WEXITSTATUS(status);
+	}
+
+	return rc;
+}
+
+
 int main(int argc, char **argv)
 {
 	int failed;
+
+	if (is_debugger_attached())
+		setenv("CK_FORK", "no", 0);
+
 	Suite *s = libevdev_has_event_test();
 	SRunner *sr = srunner_create(s);
 	srunner_add_suite(sr, libevdev_events());
-- 
1.8.4.2