Change return from MemtargetRemove, when removing the last one

previously it was OUT_OF_HOST_MEMORY, now it's INVALID_ARGUMENT.
It's aligned with other places, where we disallow creating empty memspace.
Add that requirement info to the docs.

Author: lukaszstolarczuk

include/umf/memspace.h

@@ -46,9 +46,9 @@ umfMemoryProviderCreateFromMemspace(umf_const_memspace_handle_t hMemspace,
                                     umf_const_mempolicy_handle_t hPolicy,
                                     umf_memory_provider_handle_t *hProvider);
 ///
-/// \brief Creates new memspace from array of NUMA node ids.
+/// \brief Creates new memspace from an array of NUMA node ids.
 /// \param nodeIds array of NUMA node ids
-/// \param numIds size of the array
+/// \param numIds size of the array; it has to be greater than 0
 /// \param hMemspace [out] handle to the newly created memspace
 /// \return UMF_RESULT_SUCCESS on success or appropriate error code on failure.
 ///
@@ -126,7 +126,8 @@ umf_result_t umfMemspaceMemtargetAdd(umf_memspace_handle_t hMemspace,
 ///
 /// \param hMemspace handle to memspace
 /// \param hMemtarget handle to memory target
-/// \return UMF_RESULT_SUCCESS on success or appropriate error code on failure.
+/// \return UMF_RESULT_SUCCESS on success, UMF_RESULT_ERROR_INVALID_ARGUMENT when trying to remove
+///     the last memory target from a memspace, or other appropriate error code on failure.
 ///
 umf_result_t
 umfMemspaceMemtargetRemove(umf_memspace_handle_t hMemspace,

src/memspace.c

@@ -387,6 +387,13 @@ umfMemspaceMemtargetRemove(umf_memspace_handle_t hMemspace,
     if (!hMemspace || !hMemtarget) {
         return UMF_RESULT_ERROR_INVALID_ARGUMENT;
     }
+
+    // Trying to remove the last memory target from the memspace
+    if (hMemspace->size == 1) {
+        LOG_ERR("Cannot remove the last memory target from the memspace");
+        return UMF_RESULT_ERROR_INVALID_ARGUMENT;
+    }
+
     unsigned i;
     for (i = 0; i < hMemspace->size; i++) {
         int cmp;

test/memspaces/memtarget.cpp

@@ -145,3 +145,31 @@ TEST_F(test, memTargetInvalidRemove) {
     ret = umfMemspaceDestroy(memspace);
     EXPECT_EQ(ret, UMF_RESULT_SUCCESS);
 }
+
+TEST_F(test, memTargetRemoveLast) {
+    umf_const_memspace_handle_t const_memspace = umfMemspaceHostAllGet();
+    umf_memspace_handle_t memspace = nullptr;
+    umf_result_t ret = umfMemspaceClone(const_memspace, &memspace);
+    ASSERT_EQ(ret, UMF_RESULT_SUCCESS);
+    ASSERT_NE(memspace, nullptr);
+    umf_const_memtarget_handle_t memtarget = nullptr;
+
+    // remove all memtargets except the last one
+    auto len = umfMemspaceMemtargetNum(memspace);
+    ASSERT_GT(len, 0);
+    unsigned i = len - 1;
+    for (; i > 0; i--) {
+        memtarget = umfMemspaceMemtargetGet(memspace, i);
+        EXPECT_NE(memtarget, nullptr);
+        ret = umfMemspaceMemtargetRemove(memspace, memtarget);
+        ASSERT_EQ(ret, UMF_RESULT_SUCCESS);
+    }
+
+    // removing the last memtarget is not allowed
+    memtarget = umfMemspaceMemtargetGet(memspace, i);
+    ret = umfMemspaceMemtargetRemove(memspace, memtarget);
+    EXPECT_EQ(ret, UMF_RESULT_ERROR_INVALID_ARGUMENT);
+
+    ret = umfMemspaceDestroy(memspace);
+    EXPECT_EQ(ret, UMF_RESULT_SUCCESS);
+}