tests: support testing fd inheritance over exec

Add facility for testing how (many) file descriptors survive an exec.
This allows implementing O_CLOEXEC tests.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

tests/exec-fd-leak-checker.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright © 2012 Collabora, Ltd.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <limits.h>
+
+#include "test-runner.h"
+
+static int
+parse_count(const char *str, int *value)
+{
+	char *end;
+	long v;
+
+	errno = 0;
+	v = strtol(str, &end, 0);
+	if ((errno == ERANGE && (v == LONG_MAX || v == LONG_MIN)) ||
+	    (errno != 0 && v == 0) ||
+	    (end == str) ||
+	    (*end != '\0')) {
+		return -1;
+	}
+
+	if (v < 0 || v > INT_MAX) {
+		return -1;
+	}
+
+	*value = v;
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	int expected;
+
+	if (argc != 2)
+		goto help_out;
+
+	if (parse_count(argv[1], &expected) < 0)
+		goto help_out;
+
+	if (count_open_fds() == expected)
+		return EXIT_SUCCESS;
+	else
+		return EXIT_FAILURE;
+
+help_out:
+	fprintf(stderr, "Usage: %s N\n"
+		"where N is the expected number of open file descriptors.\n"
+		"This program exits with a failure if the number "
+		"does not match exactly.\n", argv[0]);
+
+	return EXIT_FAILURE;
+}