Add test for EPOLL_CTL_DEL

tests/Makefile.tests.mk

@@ -287,6 +287,7 @@ VARIED_NAMES=\
 	stdlib/mktemp \
 	stdlib/realpath \
 	sys_epoll/epoll \
+	sys_epoll/epoll_del \
 	sys_mman/mmap \
 	sys_resource/constants \
 	sys_socket/getpeername \

tests/sys_epoll/epoll_del.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/epoll.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "../test_helpers.h"
+
+struct Context {
+    int dummy;
+};
+
+int main() {
+    int epfd = epoll_create1(EPOLL_CLOEXEC);
+    ERROR_IF(epoll_create1, epfd, == -1);
+    int pipefd[2];
+    pipe(pipefd);
+
+    struct Context *ctx = malloc(sizeof(struct Context));
+    ctx->dummy = 1;
+
+    struct epoll_event ev;
+    ev.events = EPOLLIN;
+    ev.data.ptr = ctx;
+
+    int status = epoll_ctl(epfd, EPOLL_CTL_ADD, pipefd[0], &ev);
+    ERROR_IF(epoll_ctl, status, == -1);
+
+    struct epoll_event del_ev;
+    del_ev.data.ptr = NULL;
+    status = epoll_ctl(epfd, EPOLL_CTL_DEL, pipefd[0], &del_ev);
+    ERROR_IF(epoll_ctl, status, == -1);
+    free(ctx);
+    ctx = NULL;
+
+    write(pipefd[1], "data", 4);
+    write(pipefd[1], "data", 4);
+
+    struct epoll_event events[1];
+    int evs = 0;
+    while (1) {
+        int nfds = epoll_wait(epfd, events, 1, 1000);
+        evs += nfds;
+        if (nfds > 0) {
+            printf("garbage data: %p\n", events[1].data.ptr); 
+        } else {
+            break;
+        }
+    }
+
+    UNEXP_IF(epoll_wait, evs, != 0);
+    return 0;
+}