diff --git a/src/general/ipc_msg.c b/src/general/ipc_msg.c
index 426929d..3b91aeb 100644
--- a/src/general/ipc_msg.c
+++ b/src/general/ipc_msg.c
@@ -66,7 +66,7 @@ static void snd()
 	if (qid_ds.msg_ctime < t)
 		error("qid_ds.msg_ctime >= t failed: got %ld, want %ld\n", (long)qid_ds.msg_ctime, (long)t);
 	if (qid_ds.msg_qbytes <= 0)
-		error("qid_ds.msg_qbytes > 0 failed: got %d, want 0\n", qid_ds.msg_ctime, t);
+		error("qid_ds.msg_qbytes > 0 failed: got %d, want 0\n", qid_ds.msg_qbytes, t);
 
 	/* test send */
 	T(msgsnd(qid, &msg, sizeof msg.data, IPC_NOWAIT));
diff --git a/src/general/ipc_shm.c b/src/general/ipc_shm.c
new file mode 100644
index 0000000..7d0086b
--- /dev/null
+++ b/src/general/ipc_shm.c
@@ -0,0 +1,117 @@
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 700
+#endif
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/shm.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include "test.h"
+
+static const char path[] = ".";
+static const int id = 'x';
+
+#define T(f) do{ \
+	if ((f)+1 == 0) \
+		error("%s failed: %s\n", #f, strerror(errno)); \
+}while(0)
+
+#define EQ(a,b,fmt) do{ \
+	if ((a) != (b)) \
+		error("%s == %s failed: " fmt "\n", #a, #b, a, b); \
+}while(0)
+
+static void set()
+{
+	time_t t;
+	key_t k;
+	int shmid;
+	struct shmid_ds shmid_ds;
+	void *p;
+
+	T(t = time(0));
+	T(k = ftok(path, id));
+
+	/* make sure we get a clean shared memory id */
+	T(shmid = shmget(k, 100, IPC_CREAT|0666));
+	T(shmctl(shmid, IPC_RMID, 0));
+	T(shmid = shmget(k, 100, IPC_CREAT|IPC_EXCL|0666));
+
+	if (test_status)
+		exit(test_status);
+
+	/* check IPC_EXCL */
+	errno = 0;
+	if (shmget(k, 100, IPC_CREAT|IPC_EXCL|0666) != -1 || errno != EEXIST)
+		error("shmget(IPC_CREAT|IPC_EXCL) should have failed with EEXIST, got %s\n", strerror(errno));
+
+	/* check if shmget initilaized the msshmid_ds structure correctly */
+	T(shmctl(shmid, IPC_STAT, &shmid_ds));
+	EQ(shmid_ds.shm_perm.cuid, geteuid(), "got %d, want %d");
+	EQ(shmid_ds.shm_perm.uid, geteuid(), "got %d, want %d");
+	EQ(shmid_ds.shm_perm.cgid, getegid(), "got %d, want %d");
+	EQ(shmid_ds.shm_perm.gid, getegid(), "got %d, want %d");
+	EQ(shmid_ds.shm_perm.mode & 0x1ff, 0666, "got %o, want %o");
+	EQ(shmid_ds.shm_segsz, 100, "got %d, want %d");
+	EQ(shmid_ds.shm_lpid, 0, "got %d, want %d");
+	EQ(shmid_ds.shm_cpid, getpid(), "got %d, want %d");
+	EQ((int)shmid_ds.shm_nattch, 0, "got %d, want %d");
+	EQ((long)shmid_ds.shm_atime, 0, "got %ld, want %d");
+	EQ((long)shmid_ds.shm_dtime, 0, "got %ld, want %d");
+	if (shmid_ds.shm_ctime < t)
+		error("shmid_ds.shm_ctime >= t failed: got %ld, want %ld\n", (long)shmid_ds.shm_ctime, (long)t);
+
+	/* test attach */
+	if ((p=shmat(shmid, 0, 0)) == 0)
+		error("shmat failed: %s\n", strerror(errno));
+	T(shmctl(shmid, IPC_STAT, &shmid_ds));
+	EQ((int)shmid_ds.shm_nattch, 1, "got %d, want %d");
+	EQ(shmid_ds.shm_lpid, getpid(), "got %d, want %d");
+	if (shmid_ds.shm_atime < t)
+		error("shm_atime is %ld want >= %ld\n", (long)shmid_ds.shm_atime, (long)t);
+	strcpy(p, "test data");
+	T(shmdt(p));
+}
+
+static void get()
+{
+	key_t k;
+	int shmid;
+	void *p;
+
+	T(k = ftok(path, id));
+	T(shmid = shmget(k, 0, 0));
+
+	errno = 0;
+	if ((p=shmat(shmid, 0, SHM_RDONLY)) == 0)
+		error("shmat failed: %s\n", strerror(errno));
+
+	if (strcmp(p, "test data") != 0)
+		error("reading shared mem failed: got \"%.100s\" want \"test data\"\n", p);
+
+	/* cleanup */
+	T(shmdt(p));
+	T(shmctl(shmid, IPC_RMID, 0));
+}
+
+int main(void)
+{
+	int p;
+	int status;
+
+	set();
+	p = fork();
+	if (p == -1)
+		error("fork failed: %s\n", strerror(errno));
+	else if (p == 0)
+		get();
+	else {
+		T(waitpid(p, &status, 0));
+		if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
+			error("child exit status: %d\n", status);
+	}
+	return test_status;
+}
diff --git a/src/general/sem.c b/src/general/sem.c
index 329164a..69ec34e 100644
--- a/src/general/sem.c
+++ b/src/general/sem.c
@@ -27,7 +27,6 @@ int main(void)
 		"reopening should fail with O_EXCL\n");
 	TEST(errno == EEXIST,
 		"after reopen failure errno is \"%s\" (%d); want EEXIST (%d)\n", strerror(errno), errno, EEXIST);
-	errno = 0;
 
 	TEST(sem_getvalue(sem, &val) == 0, "failed to get sem value\n");
 	TEST(val == 1, "wrong initial semaphore value: %d\n", val);
@@ -35,10 +34,15 @@ int main(void)
 	TEST((sem2=sem_open(buf, 0)) == sem,
 		"could not reopen sem: got %p, want %p\n", sem2, sem);
 
+	errno = 0;
 	TEST(sem_wait(sem) == 0, "%s\n", strerror(errno));
 	TEST(sem_getvalue(sem2, &val) == 0, "%s\n", strerror(errno));
 	TEST(val == 0, "wrong semaphore value on second handle: %d\n", val);
 
+	errno = 0;
+	TEST(sem_trywait(sem) == -1 && errno == EAGAIN,
+		"trywait on locked sem: got errno \"%s\" (%d), want EAGAIN (%d)\n", strerror(errno), errno, EAGAIN);
+
 	TEST(sem_post(sem) == 0, "%s\n", strerror(errno));
 	TEST(sem_getvalue(sem2, &val) == 0, "%s\n", strerror(errno));
 	TEST(val == 1, "wrong semaphore value on second handle: %d\n", val);