test(libc): cover overlapping UTF-16 unit moves

core/libs/prx/libc/CMakeLists.txt

@@ -406,6 +406,16 @@ if(BUILD_TESTING)
         set_tests_properties(guest_wide_conversion PROPERTIES ENVIRONMENT_MODIFICATION
             "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
     endif()
+    add_test_executable(guest_wmemmove_snapshot_tests ${LIBS_INCLUDE_DIR}/tests/GuestWmemmoveSnapshot.cpp)
+    target_include_directories(guest_wmemmove_snapshot_tests PRIVATE ${LIBS_INCLUDE_DIR})
+    target_link_libraries(guest_wmemmove_snapshot_tests PRIVATE libc)
+    configure_windows_unwind(guest_wmemmove_snapshot_tests)
+    add_test(NAME guest_wmemmove_snapshot COMMAND guest_wmemmove_snapshot_tests)
+    set_tests_properties(guest_wmemmove_snapshot PROPERTIES TIMEOUT 20)
+    if(WIN32)
+        set_tests_properties(guest_wmemmove_snapshot PROPERTIES ENVIRONMENT_MODIFICATION
+            "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
+    endif()
     add_test_executable(guest_one_runs_tests ${LIBS_INCLUDE_DIR}/tests/GuestOneRuns.cpp)
     target_include_directories(guest_one_runs_tests PRIVATE ${LIBS_INCLUDE_DIR})
     target_link_libraries(guest_one_runs_tests PRIVATE libc)

core/libs/tests/GuestWmemmoveSnapshot.cpp

@@ -0,0 +1,33 @@
+#include "prx/libc/include/Api.hpp"
+#include <algorithm>
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+#include <vector>
+
+static void Require(bool condition) {
+    if (!condition) {
+        std::fputs("GuestWmemmoveSnapshot check failed\n", stderr);
+        std::abort();
+    }
+}
+
+int main() {
+    constexpr std::array<char16_t, 8> values = {0, 1, 0xff, 0xff00, 0xd800, 0xdc00, 0xffff, 0x1234};
+    for (std::size_t count = 0; count <= 96; ++count) {
+        for (std::size_t source = 16; source <= 48; ++source) {
+            for (std::size_t destination = 16; destination <= 48; ++destination) {
+                std::array<char16_t, 192> original{};
+                for (std::size_t i = 0; i < original.size(); ++i) original[i] = values[(i + count) % values.size()];
+                auto actual = original, expected = original;
+                for (std::size_t i = 0; i < count; ++i) expected[destination + i] = original[source + i];
+                Require(wmemmove_nid_postfix(actual.data() + destination, actual.data() + source, count) == actual.data() + destination);
+                Require(actual == expected);
+            }
+        }
+    }
+}