[test] Attempt to automatically detect running under gdb

A common mistake is to forget to pass the foreground mode to
cairo-test-suite when launching it under the debugger, resulting in the
debugger not attaching to the children and missing the error you were
trying to capture. Under linux, we can inspect the path to our parent's
executable and if that looks like gdb, we assume it is and disable forking
of traces.

1 files changed, 32 insertions, 0 deletions

diff --git a/test/cairo-test-runner.c b/test/cairo-test-runner.c
index f147b5b73..af2991a2e 100644
--- a/test/cairo-test-runner.c
+++ b/test/cairo-test-runner.c
@@ -49,6 +49,15 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #endif
+#if HAVE_LIBGEN_H
+#include <libgen.h>
+#endif
+
+#if HAVE_VALGRIND
+#include <valgrind.h>
+#else
+#define RUNNING_ON_VALGRIND 0
+#endif
 
 #ifdef _MSC_VER
 #include <crtdbg.h>
@@ -146,6 +155,26 @@ _list_free (cairo_test_list_t *list)
     }
 }
 
+static cairo_bool_t
+is_running_under_debugger (void)
+{
+    char buf[1024];
+
+    if (RUNNING_ON_VALGRIND)
+	return TRUE;
+
+#if HAVE_UNISTD_H && HAVE_LIBGEN_H && __linux__
+    sprintf (buf, "/proc/%d/exe", getppid ());
+    if (readlink (buf, buf, sizeof (buf)) != -1 &&
+	strncmp (basename (buf), "gdb", 3) == 0)
+    {
+	return TRUE;
+    }
+#endif
+
+    return FALSE;
+}
+
 #if SHOULD_FORK
 static cairo_test_status_t
 _cairo_test_wait (pid_t pid)
@@ -621,6 +650,9 @@ main (int argc, char **argv)
     memset (&runner, 0, sizeof (runner));
     runner.num_device_offsets = 1;
 
+    if (is_running_under_debugger ())
+	runner.foreground = TRUE;
+
     if (getenv ("CAIRO_TEST_MODE")) {
 	const char *env = getenv ("CAIRO_TEST_MODE");