fix: another segfault in 64 bit deserialize_safe (#664)

actually update the previous_high32 variable to ensure the ghigh keys are
actually strictly increasing

src/roaring64.c

@@ -1970,6 +1970,8 @@ roaring64_bitmap_t *roaring64_bitmap_portable_deserialize_safe(
             roaring64_bitmap_free(r);
             return NULL;
         }
+        previous_high32 = high32;
+
         // Read the 32-bit Roaring bitmaps representing the least significant
         // bits of a set of elements.
         size_t bitmap32_size = roaring_bitmap_portable_deserialize_size(

tests/roaring64_serialization.cpp

@@ -97,7 +97,7 @@ DEFINE_TEST(test_64deseroverlappingkeys) {
         // Container count - 1
         1, 0,
         // Run Flag Bitset (no runs)
-        0, 0,
+        0,
         // Upper 16 bits of the first container
         0, 0,
         // Cardinality - 1 of the first container
@@ -125,6 +125,56 @@ DEFINE_TEST(test_64deseroverlappingkeys) {
         roaring64_bitmap_free(r);
     }
 }
+
+DEFINE_TEST(test_64deseroverlappingupper32) {
+    // Two bitmaps, with a single array container each, at the same key (0).
+    // clang-format off
+    char simple_bitmap[] = {
+        // Number of 32 bit bitmaps
+        2, 0, 0, 0, 0, 0, 0, 0,
+        // Top 32 bits of the first bitmap
+        0,  0,  0, 0,
+        // Serial Cookie
+        0x3B, 0x30,
+        // Container count - 1
+        0, 0,
+        // Run Flag Bitset (not a run)
+        0,
+        // Upper 16 bits of the only container
+        0, 0,
+        // Cardinality - 1 of the only container
+        0, 0,
+        // Only value of first container
+        0, 0,
+        // Top 32 bits of the second bitmap
+        0, 0, 0, 0,
+        // Serial Cookie
+        0x3B, 0x30,
+        // Container count - 1
+        0, 0,
+        // Run Flag Bitset (not a run)
+        0,
+        // Upper 16 bits of the only container
+        0, 0,
+        // Cardinality - 1 of the only container
+        0, 0,
+        // Only value of only container
+        0, 0,
+    };
+    // clang-format on
+
+    roaring64_bitmap_t* r = roaring64_bitmap_portable_deserialize_safe(
+        simple_bitmap, sizeof(simple_bitmap));
+    const char* reason = nullptr;
+    if (r != nullptr) {
+        if (roaring64_bitmap_internal_validate(r, &reason)) {
+            fail_msg(
+                "Validation must fail if a bitmap was returned, duplicate keys "
+                "are not allowed.");
+        }
+        roaring64_bitmap_free(r);
+    }
+}
 }  // namespace
 
 int main() {
@@ -142,6 +192,7 @@ int main() {
         cmocka_unit_test(test_64mapsizetoosmall),
         cmocka_unit_test(test_64mapspreadvals),
         cmocka_unit_test(test_64deseroverlappingkeys),
+        cmocka_unit_test(test_64deseroverlappingupper32),
     };
     return cmocka_run_group_tests(tests, NULL, NULL);
 #endif  // CROARING_IS_BIG_ENDIAN