[PATCH 4/4] tests/tcg: Test shmat(NULL)

[Ilya Leoshkevich]

Add a small test to prevent regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tests/tcg/multiarch/linux/linux-shmat-null.c | 38 ++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 tests/tcg/multiarch/linux/linux-shmat-null.c

diff --git a/tests/tcg/multiarch/linux/linux-shmat-null.c 
b/tests/tcg/multiarch/linux/linux-shmat-null.c
new file mode 100644
index 00000000000..94eaaec371a
--- /dev/null
+++ b/tests/tcg/multiarch/linux/linux-shmat-null.c
@@ -0,0 +1,38 @@
+/*
+ * Test shmat(NULL).
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <assert.h>
+#include <stdlib.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+
+int main(void)
+{
+    int shmid;
+    char *p;
+    int err;
+
+    /* Create, attach and intialize shared memory. */
+    shmid = shmget(IPC_PRIVATE, 1, IPC_CREAT | 0600);
+    assert(shmid != -1);
+    p = shmat(shmid, NULL, 0);
+    assert(p != (void *)-1);
+    *p = 42;
+
+    /* Reattach, check that the value is still there. */
+    err = shmdt(p);
+    assert(err == 0);
+    p = shmat(shmid, NULL, 0);
+    assert(p != (void *)-1);
+    assert(*p == 42);
+
+    /* Detach. */
+    err = shmdt(p);
+    assert(err == 0);
+    err = shmctl(shmid, IPC_RMID, NULL);
+    assert(err == 0);
+
+    return EXIT_SUCCESS;
+}
-- 
2.44.0