failtest: don't assume FD_SETSIZE is maximum runtime fd.

This breaks when rlimit is less.  Unfortunately, valgrind (32 bit x86,
3.7.0.SVN, Ubuntu) fails to set the file limit properly on the test:
reducing it to the obvious getrlimit/setrlimit/getrlimit works fine,
so leaving diagnostics for another day.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(Imported from CCAN commit a85a809bb17af6b6cf6fa31b300c6622f64ee700)

Autobuild-User: Rusty Russell <rusty@rustcorp.com.au>
Autobuild-Date: Thu Mar  8 06:30:48 CET 2012 on sn-devel-104

1 files changed, 51 insertions, 0 deletions

diff --git a/lib/ccan/failtest/test/run-with-fdlimit.c b/lib/ccan/failtest/test/run-with-fdlimit.c
new file mode 100644
index 0000000000..6b4483f07e
--- /dev/null
+++ b/lib/ccan/failtest/test/run-with-fdlimit.c
@@ -0,0 +1,51 @@
+/* Include the C files directly. */
+#include <ccan/failtest/failtest.c>
+#include <stdlib.h>
+#include <err.h>
+#include <ccan/tap/tap.h>
+
+int main(void)
+{
+	int fd, pfd[2], ecode;
+	struct rlimit lim;
+
+	if (getrlimit(RLIMIT_NOFILE, &lim) != 0)
+		err(1, "getrlimit RLIMIT_NOFILE fail?");
+
+	printf("rlimit = %lu/%lu (inf=%lu)\n",
+	       (long)lim.rlim_cur, (long)lim.rlim_max,
+	       (long)RLIM_INFINITY);
+	lim.rlim_cur /= 2;
+	if (lim.rlim_cur < 8)
+		errx(1, "getrlimit limit %li too low", (long)lim.rlim_cur);
+	if (setrlimit(RLIMIT_NOFILE, &lim) != 0)
+		err(1, "setrlimit RLIMIT_NOFILE (%li/%li)",
+		    (long)lim.rlim_cur, (long)lim.rlim_max);
+
+	plan_tests(2);
+	failtest_init(0, NULL);
+
+	if (pipe(pfd))
+		abort();
+
+	fd = failtest_open("run-with-fdlimit-scratch", "run-with_fdlimit.c", 1,
+			   O_RDWR|O_CREAT, 0600);
+	if (fd == -1) {
+		/* We are the child: write error code for parent to check. */
+		ecode = errno;
+		if (write(pfd[1], &ecode, sizeof(ecode)) != sizeof(ecode))
+			abort();
+		failtest_exit(0);
+	}
+
+	/* Check child got correct errno. */
+	ok1(read(pfd[0], &ecode, sizeof(ecode)) == sizeof(ecode));
+	ok1(ecode == EACCES);
+
+	/* Clean up. */
+	failtest_close(fd, "run-open.c", 1);
+	close(pfd[0]);
+	close(pfd[1]);
+
+	return exit_status();
+}