update check-structures-sanity (part 2 of 2)

2020-03-10 23:05:59 -05:00 · 2020-03-10 23:05:59 -05:00 · e2138a6cc2
parent e5de783c58
commit e2138a6cc2
5 changed files with 674 additions and 81 deletions
--- a/plugins/devel/check-structures-sanity/check-structures-sanity.h
+++ b/plugins/devel/check-structures-sanity/check-structures-sanity.h
@ -15,7 +15,7 @@ using namespace DFHack;
 #ifdef WIN32
 #define UNEXPECTED __debugbreak()
 #else
-#define UNEXPECTED __asm__ volatile ("int $0x03")
+#define UNEXPECTED __asm__ volatile ("int $0x03; nop")
 #endif

 #define PTR_ADD(ptr, offset) reinterpret_cast<const void *>(uintptr_t(ptr) + (offset))
@ -33,14 +33,20 @@ struct CheckedStructure
 {
    type_identity *identity;
    size_t count;
+    enum_identity *eid;

    CheckedStructure();
    explicit CheckedStructure(type_identity *, size_t = 0);
+    CheckedStructure(type_identity *, size_t, enum_identity *);
    CheckedStructure(const struct_field_info *);

    size_t full_size() const;
 };

+#define MIN_SIZE_FOR_SUGGEST 64
+extern std::map<size_t, std::vector<std::string>> known_types_by_size;
+void build_size_table();
+
 namespace
 {
    template<typename T, bool is_pointer = std::is_pointer<T>::value>
@ -59,7 +65,7 @@ class Checker
 {
    color_ostream & out;
    std::vector<t_memrange> mapped;
-    std::map<const void *, CheckedStructure> data;
+    std::map<const void *, std::pair<std::string, CheckedStructure>> data;
    std::deque<QueueItem> queue;
 public:
    size_t checked_count;
@ -72,11 +78,19 @@ public:
    bool failfast;

    Checker(color_ostream & out);
-    void queue_item(const QueueItem & item, const CheckedStructure & cs);
+    bool queue_item(const QueueItem & item, const CheckedStructure & cs);
    void queue_globals();
    bool process_queue();

-    bool is_valid_dereference(const QueueItem & item, const CheckedStructure & cs, bool quiet = false);
+    bool is_valid_dereference(const QueueItem & item, const CheckedStructure & cs, size_t size, bool quiet);
+    inline bool is_valid_dereference(const QueueItem & item, const CheckedStructure & cs, bool quiet = false)
+    {
+        return is_valid_dereference(item, cs, cs.full_size(), quiet);
+    }
+    inline bool is_valid_dereference(const QueueItem & item, size_t size, bool quiet = false)
+    {
+        return is_valid_dereference(item, CheckedStructure(df::identity_traits<void *>::get()), size, quiet);
+    }
    template<typename T>
    const T validate_and_dereference(const QueueItem & item, bool quiet = false)
    {
@ -87,8 +101,15 @@ public:

        return *reinterpret_cast<const T *>(item.ptr);
    }
+    int64_t get_int_value(const QueueItem & item, type_identity *type, bool quiet = false);
    const char *get_vtable_name(const QueueItem & item, const CheckedStructure & cs, bool quiet = false);
    std::pair<const void *, size_t> validate_vector_size(const QueueItem & item, const CheckedStructure & cs, bool quiet = false);
+    size_t get_allocated_size(const QueueItem & item);
+#ifndef WIN32
+    // this function doesn't make sense on windows, where std::string is not pointer-sized.
+    const std::string *validate_stl_string_pointer(const void *const*);
+#endif
+    static const char *const *get_enum_item_key(enum_identity *identity, int64_t value);

 private:
    color_ostream & fail(int, const QueueItem &, const CheckedStructure &);
@ -106,12 +127,25 @@ private:
    void dispatch_class(const QueueItem &, const CheckedStructure &);
    void dispatch_buffer(const QueueItem &, const CheckedStructure &);
    void dispatch_stl_ptr_vector(const QueueItem &, const CheckedStructure &);
+    void dispatch_tagged_union(const QueueItem &, const QueueItem &, const CheckedStructure &, const CheckedStructure &);
+    void dispatch_tagged_union_vector(const QueueItem &, const QueueItem &, const CheckedStructure &, const CheckedStructure &);
    void dispatch_untagged_union(const QueueItem &, const CheckedStructure &);
-    void check_stl_vector(const QueueItem &, type_identity *);
+    void check_unknown_pointer(const QueueItem &);
+    void check_stl_vector(const QueueItem &, type_identity *, type_identity *);
+    void check_stl_string(const QueueItem &);

    friend struct CheckedStructure;
    static type_identity *wrap_in_pointer(type_identity *);
    static type_identity *wrap_in_stl_ptr_vector(type_identity *);
 };

-#define FAIL(message) (static_cast<color_ostream &>(fail(__LINE__, item, cs) << message) << COLOR_RESET << std::endl)
+#define FAIL(message) \
+    do \
+    { \
+        auto & failstream = fail(__LINE__, item, cs); \
+        failstream << message; \
+        failstream << COLOR_RESET << std::endl; \
+        if (failfast) \
+            UNEXPECTED; \
+    } \
+    while (false)
--- a/plugins/devel/check-structures-sanity/dispatch.cpp
+++ b/plugins/devel/check-structures-sanity/dispatch.cpp
@ -25,19 +25,25 @@ color_ostream & Checker::fail(int line, const QueueItem & item, const CheckedStr
    out << COLOR_YELLOW;
    if (maxerrors && maxerrors != ~size_t(0))
        maxerrors--;
-    if (failfast)
-        UNEXPECTED;
    return out;
 }

-void Checker::queue_item(const QueueItem & item, const CheckedStructure & cs)
+bool Checker::queue_item(const QueueItem & item, const CheckedStructure & cs)
 {
-    if (data.count(item.ptr) && data.at(item.ptr).full_size() == cs.full_size())
+    if (data.count(item.ptr))
    {
        // already checked
-        // TODO: make sure types are equal
-        UNEXPECTED;
-        return;
+        auto existing = data.at(item.ptr);
+        if (cs.identity != existing.second.identity)
+        {
+            if (cs.identity->type() == IDTYPE_CLASS && existing.second.identity->type() == IDTYPE_CLASS && get_vtable_name(item, cs, false) && static_cast<virtual_identity *>(cs.identity)->is_instance(static_cast<virtual_ptr>(const_cast<void *>(item.ptr))))
+            {
+                return false;
+            }
+
+            FAIL("TODO: handle merging structures: " << data.at(item.ptr).first << " overlaps " << item.path << " (same pointer)");
+        }
+        return false;
    }

    auto ptr_end = PTR_ADD(item.ptr, cs.full_size());
@ -46,24 +52,42 @@ void Checker::queue_item(const QueueItem & item, const CheckedStructure & cs)
    if (prev != data.cbegin())
    {
        prev--;
-        if (uintptr_t(prev->first) + prev->second.full_size() > uintptr_t(item.ptr))
+        if (uintptr_t(prev->first) + prev->second.second.full_size() > uintptr_t(item.ptr))
        {
-            // TODO
+            // placeholder algorithm
+            if (auto sid = dynamic_cast<struct_identity *>(prev->second.second.identity))
+            {
+                auto offset = uintptr_t(item.ptr) - uintptr_t(prev->first);
+                for (auto field = sid->getFields(); field->mode != struct_field_info::END; field++)
+                {
+                    if (field->offset == offset)
+                    {
+                        if (field->mode == struct_field_info::SUBSTRUCT && field->type == cs.identity)
+                        {
+                            return false;
+                        }
+
                        UNEXPECTED;
                    }
                }
+            }
+            // TODO
+            FAIL("TODO: handle merging structures: " << prev->second.first << " overlaps " << item.path << " (backward)");
+        }
+    }

    auto overlap = data.lower_bound(item.ptr);
    auto overlap_end = data.lower_bound(ptr_end);
    while (overlap != overlap_end)
    {
        // TODO
-        UNEXPECTED;
+        FAIL("TODO: handle merging structures: " << overlap->second.first << " overlaps " << item.path << " (forward)");
        overlap++;
    }

-    data[item.ptr] = cs;
+    data[item.ptr] = std::make_pair(item.path, cs);
    queue.push_back(item);
+    return true;
 }

 void Checker::queue_globals()
@ -89,6 +113,12 @@ void Checker::queue_globals()
            continue;
        }

+        if (!strcmp(field->name, "enabler"))
+        {
+            // don't care about libgraphics as we have the source code
+            continue;
+        }
+
        queue_item(item, cs);
    }
 }
@ -110,7 +140,7 @@ bool Checker::process_queue()
        return true;
    }

-    dispatch_item(item, cs->second);
+    dispatch_item(item, cs->second.second);

    return true;
 }
@ -194,7 +224,6 @@ void Checker::dispatch_single_item(const QueueItem & item, const CheckedStructur
            dispatch_stl_ptr_vector(item, cs);
            break;
        case IDTYPE_OPAQUE:
-            UNEXPECTED;
            break;
        case IDTYPE_UNION:
            dispatch_untagged_union(item, cs);
@ -203,28 +232,79 @@ void Checker::dispatch_single_item(const QueueItem & item, const CheckedStructur
 }

 void Checker::dispatch_primitive(const QueueItem & item, const CheckedStructure & cs)
-{
-    if (cs.identity->isConstructed())
 {
    if (cs.identity == df::identity_traits<std::string>::get())
    {
-            // TODO check std::string
+        check_stl_string(item);
+    }
+    else if (cs.identity == df::identity_traits<char *>::get())
+    {
+        // TODO check c strings
        UNEXPECTED;
    }
+    else if (cs.identity == df::identity_traits<bool>::get())
+    {
+        auto val = *reinterpret_cast<const uint8_t *>(item.ptr);
+        if (val > 1 && val != 0xd2)
+        {
+            FAIL("invalid value for bool: " << int(val));
+        }
+    }
+    else if (auto int_id = dynamic_cast<df::integer_identity_base *>(cs.identity))
+    {
+        // TODO check ints?
+    }
+    else if (auto float_id = dynamic_cast<df::float_identity_base *>(cs.identity))
+    {
+        // TODO check floats?
+    }
    else
    {
        UNEXPECTED;
    }
 }
+void Checker::dispatch_pointer(const QueueItem & item, const CheckedStructure & cs)
+{
+    auto target_ptr = validate_and_dereference<const void *>(item);
+    if (!target_ptr)
+    {
+        return;
+    }

-    // TODO: check primitives
-    UNEXPECTED;
+#ifdef DFHACK64
+    if (uintptr_t(target_ptr) == 0xd2d2d2d2d2d2d2d2)
+#else
+    if (uintptr_t(target_ptr) == 0xd2d2d2d2)
+#endif
+    {
+        return;
    }
-void Checker::dispatch_pointer(const QueueItem & item, const CheckedStructure & cs)
+
+    QueueItem target_item(item.path, target_ptr);
+    auto target = static_cast<pointer_identity *>(cs.identity)->getTarget();
+    if (!target)
    {
-    auto identity = static_cast<pointer_identity *>(cs.identity);
-    // TODO: check pointer
-    UNEXPECTED;
+        check_unknown_pointer(item);
+        return;
+    }
+
+    // 256 is an arbitrarily chosen size threshold
+    if (cs.count || target->byte_size() <= 256)
+    {
+        // target is small, or we are inside an array of pointers; handle now
+        if (queue_item(target_item, CheckedStructure(target)))
+        {
+            // we insert it into the queue to make sure we're not stuck in a loop
+            // get it back out of the queue to prevent the queue growing too big
+            queue.pop_back();
+            dispatch_item(target_item, CheckedStructure(target));
+        }
+    }
+    else
+    {
+        // target is large and not part of an array; handle later
+        queue_item(target_item, CheckedStructure(target));
+    }
 }
 void Checker::dispatch_container(const QueueItem & item, const CheckedStructure & cs)
 {
@ -232,11 +312,7 @@ void Checker::dispatch_container(const QueueItem & item, const CheckedStructure
    auto base_container = identity->getFullName(nullptr);
    if (base_container == "vector<void>")
    {
-        if (identity->getIndexEnumType())
-        {
-            UNEXPECTED;
-        }
-        check_stl_vector(item, identity->getItemType());
+        check_stl_vector(item, identity->getItemType(), identity->getIndexEnumType());
    }
    else if (base_container == "deque<void>")
    {
@ -262,12 +338,10 @@ void Checker::dispatch_bit_container(const QueueItem & item, const CheckedStruct
    if (base_container == "BitArray<>")
    {
        // TODO: check DF bit array
-        UNEXPECTED;
    }
    else if (base_container == "vector<bool>")
    {
        // TODO: check stl bit vector
-        UNEXPECTED;
    }
    else
    {
@ -281,8 +355,66 @@ void Checker::dispatch_bitfield(const QueueItem & item, const CheckedStructure &
        return;
    }

-    // TODO: check bitfields
+    auto bitfield_type = static_cast<bitfield_identity *>(cs.identity);
+    uint64_t bitfield_value;
+    switch (bitfield_type->byte_size())
+    {
+        case 1:
+            bitfield_value = validate_and_dereference<uint8_t>(item);
+            // don't check for uninitialized; too small to be sure
+            break;
+        case 2:
+            bitfield_value = validate_and_dereference<uint16_t>(item);
+            if (bitfield_value == 0xd2d2)
+            {
+                bitfield_value = 0;
+            }
+            break;
+        case 4:
+            bitfield_value = validate_and_dereference<uint32_t>(item);
+            if (bitfield_value == 0xd2d2d2d2)
+            {
+                bitfield_value = 0;
+            }
+            break;
+        case 8:
+            bitfield_value = validate_and_dereference<uint64_t>(item);
+            if (bitfield_value == 0xd2d2d2d2d2d2d2d2)
+            {
+                bitfield_value = 0;
+            }
+            break;
+        default:
            UNEXPECTED;
+            bitfield_value = 0;
+            break;
+    }
+
+    auto num_bits = bitfield_type->getNumBits();
+    auto bits = bitfield_type->getBits();
+    for (int i = 0; i < 64; i++)
+    {
+        if (!(num_bits & 1))
+        {
+            bitfield_value >>= 1;
+            continue;
+        }
+
+        bitfield_value >>= 1;
+
+        if (i >= num_bits || !bits[i].size)
+        {
+            FAIL("bitfield bit " << i << " is out of range");
+        }
+        else if (unnamed && bits[i].size > 0 && !bits[i].name)
+        {
+            FAIL("bitfield bit " << i << " is unnamed");
+        }
+        else if (unnamed && !bits[i + bits[i].size].name)
+        {
+            FAIL("bitfield bit " << i << " (part of a field starting at bit " << (i + bits[i].size) << ") is unnamed");
+        }
+    }
 }
 void Checker::dispatch_enum(const QueueItem & item, const CheckedStructure & cs)
 {
@ -291,8 +423,31 @@ void Checker::dispatch_enum(const QueueItem & item, const CheckedStructure & cs)
        return;
    }

-    // TODO: check enums
-    UNEXPECTED;
+    auto enum_type = static_cast<enum_identity *>(cs.identity);
+    auto enum_value = get_int_value(item, enum_type->getBaseType());
+    if (enum_type->byte_size() == 2 && uint16_t(enum_value) == 0xd2d2)
+    {
+        return;
+    }
+    else if (enum_type->byte_size() == 4 && uint32_t(enum_value) == 0xd2d2d2d2)
+    {
+        return;
+    }
+    else if (enum_type->byte_size() == 8 && uint64_t(enum_value) == 0xd2d2d2d2d2d2d2d2)
+    {
+        return;
+    }
+
+    auto enum_name = get_enum_item_key(enum_type, enum_value);
+    if (!enum_name)
+    {
+        FAIL("enum value (" << enum_value << ") is out of range");
+        return;
+    }
+    if (unnamed && !*enum_name)
+    {
+        FAIL("enum value (" << enum_value << ") is unnamed");
+    }
 }
 void Checker::dispatch_struct(const QueueItem & item, const CheckedStructure & cs)
 {
@ -300,6 +455,11 @@ void Checker::dispatch_struct(const QueueItem & item, const CheckedStructure & c
    for (auto p = identity; p; p = p->getParent())
    {
        auto fields = p->getFields();
+        if (!fields)
+        {
+            continue;
+        }
+
        for (auto field = fields; field->mode != struct_field_info::END; field++)
        {
            dispatch_field(item, cs, fields, field);
@ -314,16 +474,28 @@ void Checker::dispatch_field(const QueueItem & item, const CheckedStructure & cs
        return;
    }

+    auto field_ptr = PTR_ADD(item.ptr, field->offset);
+    QueueItem field_item(item, field->name, field_ptr);
+    CheckedStructure field_cs(field);
+
    auto tag_field = find_union_tag(fields, field);
    if (tag_field)
    {
-        UNEXPECTED;
+        auto tag_ptr = PTR_ADD(item.ptr, tag_field->offset);
+        QueueItem tag_item(item, tag_field->name, tag_ptr);
+        CheckedStructure tag_cs(tag_field);
+        if (tag_cs.identity->isContainer())
+        {
+            dispatch_tagged_union_vector(field_item, tag_item, field_cs, tag_cs);
+        }
+        else
+        {
+            dispatch_tagged_union(field_item, tag_item, field_cs, tag_cs);
+        }
        return;
    }

-    auto field_ptr = PTR_ADD(item.ptr, field->offset);
-    CheckedStructure field_cs(field);
-    dispatch_item(QueueItem(item, field->name, field_ptr), field_cs);
+    dispatch_item(field_item, field_cs);
 }
 void Checker::dispatch_class(const QueueItem & item, const CheckedStructure & cs)
 {
@ -336,40 +508,158 @@ void Checker::dispatch_class(const QueueItem & item, const CheckedStructure & cs

    auto base_identity = static_cast<virtual_identity *>(cs.identity);
    auto vptr = static_cast<virtual_ptr>(const_cast<void *>(item.ptr));
-    if (!base_identity->is_instance(vptr))
+    auto identity = virtual_identity::get(vptr);
+    if (!identity)
+    {
+        FAIL("unidentified subclass of " << base_identity->getFullName() << ": " << vtable_name);
+        return;
+    }
+    if (base_identity != identity && !base_identity->is_subclass(identity))
    {
-        FAIL("expected subclass of " << base_identity->getFullName() << ", but got " << vtable_name);
+        FAIL("expected subclass of " << base_identity->getFullName() << ", but got " << identity->getFullName());
        return;
    }

-    auto identity = virtual_identity::get(vptr);
+    if (data.count(item.ptr) && data.at(item.ptr).first == item.path)
+    {
+        // TODO: handle cases where this may overlap later data
+        data.at(item.ptr).second.identity = identity;
+    }
+
    dispatch_struct(QueueItem(item.path + "<" + identity->getFullName() + ">", item.ptr), CheckedStructure(identity));
 }
 void Checker::dispatch_buffer(const QueueItem & item, const CheckedStructure & cs)
 {
    auto identity = static_cast<container_identity *>(cs.identity);
-    if (identity->getIndexEnumType())
-    {
-        UNEXPECTED;
-    }

    auto item_identity = identity->getItemType();
-    dispatch_item(item, CheckedStructure(item_identity, identity->byte_size() / item_identity->byte_size()));
+    dispatch_item(item, CheckedStructure(item_identity, identity->byte_size() / item_identity->byte_size(), static_cast<enum_identity *>(identity->getIndexEnumType())));
 }
 void Checker::dispatch_stl_ptr_vector(const QueueItem & item, const CheckedStructure & cs)
 {
    auto identity = static_cast<container_identity *>(cs.identity);
-    if (identity->getIndexEnumType())
+    auto ptr_type = wrap_in_pointer(identity->getItemType());
+    check_stl_vector(item, ptr_type, identity->getIndexEnumType());
+}
+void Checker::dispatch_tagged_union(const QueueItem & item, const QueueItem & tag_item, const CheckedStructure & cs, const CheckedStructure & tag_cs)
+{
+    if (tag_cs.identity->type() != IDTYPE_ENUM || cs.identity->type() != IDTYPE_UNION)
+    {
+        UNEXPECTED;
+        return;
+    }
+
+    auto tag_identity = static_cast<enum_identity *>(tag_cs.identity);
+    auto tag_value = get_int_value(tag_item, tag_identity->getBaseType());
+    auto tag_name = get_enum_item_key(tag_identity, tag_value);
+    if (!tag_name)
+    {
+        FAIL("tagged union tag (accessed as " << tag_item.path << ") value (" << tag_value << ") not defined in enum " << tag_cs.identity->getFullName());
+        return;
+    }
+
+    if (!*tag_name)
+    {
+        FAIL("tagged union tag (accessed as " << tag_item.path << ") value (" << tag_value << ") is unnamed");
+        return;
+    }
+
+    auto union_type = static_cast<union_identity *>(cs.identity);
+    for (auto field = union_type->getFields(); field->mode != struct_field_info::END; field++)
+    {
+        if (strcmp(field->name, *tag_name))
+        {
+            continue;
+        }
+
+        if (field->offset != 0)
+        {
+            UNEXPECTED;
+        }
+
+        dispatch_item(QueueItem(item, field->name, item.ptr), field);
+        return;
+    }
+
+    auto union_data_ptr = reinterpret_cast<const uint8_t *>(item.ptr);
+    uint8_t padding_byte = *union_data_ptr;
+    if (padding_byte == 0x00 || padding_byte == 0xd2 || padding_byte == 0xff)
+    {
+        bool all_padding = true;
+        for (size_t i = 0; i < union_type->byte_size(); i++)
+        {
+            if (union_data_ptr[i] != padding_byte)
+            {
+                all_padding = false;
+                break;
+            }
+        }
+
+        // don't ask for fields if it's all padding
+        if (all_padding)
+        {
+            return;
+        }
+    }
+
+    FAIL("tagged union missing " << *tag_name << " field to match tag (accessed as " << tag_item.path << ") value (" << tag_value << ")");
+}
+void Checker::dispatch_tagged_union_vector(const QueueItem & item, const QueueItem & tag_item, const CheckedStructure & cs, const CheckedStructure & tag_cs)
+{
+    auto union_container_identity = static_cast<container_identity *>(cs.identity);
+    CheckedStructure union_item_cs(union_container_identity->getItemType());
+    if (union_container_identity->type() != IDTYPE_CONTAINER)
+    {
+        // assume pointer container
+        union_item_cs.identity = wrap_in_pointer(union_item_cs.identity);
+    }
+
+    auto tag_container_identity = static_cast<container_identity *>(tag_cs.identity);
+    auto tag_container_base = tag_container_identity->getFullName(nullptr);
+    if (tag_container_base == "vector<void>")
+    {
+        auto vec_union = validate_vector_size(item, union_item_cs);
+        CheckedStructure tag_item_cs(tag_container_identity->getItemType());
+        auto vec_tag = validate_vector_size(tag_item, tag_item_cs);
+        if (!vec_union.first || !vec_tag.first)
+        {
+            // invalid vectors (already warned)
+            return;
+        }
+        if (!vec_union.second && !vec_tag.second)
+        {
+            // empty vectors
+            return;
+        }
+        if (vec_union.second != vec_tag.second)
+        {
+            FAIL("tagged union vector is " << vec_union.second << " elements, but tag vector (accessed as " << tag_item.path << ") is " << vec_tag.second << " elements");
+        }
+
+        for (size_t i = 0; i < vec_union.second && i < vec_tag.second; i++)
+        {
+            dispatch_tagged_union(QueueItem(item, i, vec_union.first), QueueItem(tag_item, i, vec_tag.first), union_item_cs, tag_item_cs);
+            vec_union.first = PTR_ADD(vec_union.first, union_item_cs.identity->byte_size());
+            vec_tag.first = PTR_ADD(vec_tag.first, tag_item_cs.identity->byte_size());
+        }
+    }
+    else if (tag_container_base == "vector<bool>")
+    {
+        // TODO
+        UNEXPECTED;
+    }
+    else
    {
        UNEXPECTED;
    }
-    auto ptr_type = wrap_in_pointer(identity->getItemType());
-    check_stl_vector(item, ptr_type);
 }
 void Checker::dispatch_untagged_union(const QueueItem & item, const CheckedStructure & cs)
 {
+    // special case for large_integer weirdness
    if (cs.identity == df::identity_traits<df::large_integer>::get())
    {
+        // it's 16 bytes on 64-bit linux due to a messy header in libgraphics
+        // but only the first 8 bytes are ever used
        dispatch_primitive(item, CheckedStructure(df::identity_traits<int64_t>::get()));
        return;
    }
@ -377,13 +667,141 @@ void Checker::dispatch_untagged_union(const QueueItem & item, const CheckedStruc
    UNEXPECTED;
 }

-void Checker::check_stl_vector(const QueueItem & item, type_identity *item_identity)
+void Checker::check_unknown_pointer(const QueueItem & item)
+{
+    CheckedStructure cs(df::identity_traits<void *>::get());
+    if (auto allocated_size = get_allocated_size(item))
+    {
+        FAIL("pointer to a block of " << allocated_size << " bytes of allocated memory");
+        if (allocated_size >= MIN_SIZE_FOR_SUGGEST && known_types_by_size.count(allocated_size))
+        {
+            FAIL("known types of this size: " << join_strings(", ", known_types_by_size.at(allocated_size)));
+        }
+
+        // check recursively if it's the right size for a pointer
+        // or if it starts with what might be a valid pointer
+        if (allocated_size == sizeof(void *) || (allocated_size > sizeof(void *) && is_valid_dereference(item, cs, true)))
+        {
+            QueueItem ptr_item(item, "?ptr?", item.ptr);
+            if (queue_item(ptr_item, cs))
+            {
+                queue.pop_back();
+                dispatch_pointer(ptr_item, cs);
+            }
+        }
+    }
+#ifndef WIN32
+    else if (auto str = validate_stl_string_pointer(&item.ptr))
+    {
+        FAIL("untyped pointer is actually stl-string with value \"" << *str << "\" (length " << str->length() << ")");
+    }
+#endif
+    else if (auto vtable_name = get_vtable_name(QueueItem(item.path, &item.ptr), cs, true))
+    {
+        FAIL("pointer to a vtable: " << vtable_name);
+    }
+    else if (sizes)
+    {
+        //FAIL("pointer to memory with no size information");
+    }
+}
+
+void Checker::check_stl_vector(const QueueItem & item, type_identity *item_identity, type_identity *eid)
 {
    auto vec_items = validate_vector_size(item, CheckedStructure(item_identity));
+
+    // skip bad pointer vectors
+    if (item.path.length() > 4 && item.path.substr(item.path.length() - 4) == ".bad" && item_identity->type() == IDTYPE_POINTER)
+    {
+        return;
+    }
+
    if (vec_items.first && vec_items.second)
    {
        QueueItem items_item(item.path, vec_items.first);
-        CheckedStructure items_cs(item_identity, vec_items.second);
+        CheckedStructure items_cs(item_identity, vec_items.second, static_cast<enum_identity *>(eid));
        queue_item(items_item, items_cs);
    }
 }
+
+void Checker::check_stl_string(const QueueItem & item)
+{
+    const static CheckedStructure cs(df::identity_traits<std::string>::get());
+
+#ifdef WIN32
+    struct string_data
+    {
+        union
+        {
+            uintptr_t start;
+            char local_data[16];
+        };
+        size_t length;
+        size_t capacity;
+    };
+#else
+    struct string_data
+    {
+        struct string_data_inner
+        {
+            size_t length;
+            size_t capacity;
+            int32_t refcount;
+        } *ptr;
+    };
+#endif
+
+    auto string = reinterpret_cast<const string_data *>(item.ptr);
+#ifdef WIN32
+    bool is_local = string->capacity < 16;
+    const char *start = is_local ? &string->local_data[0] : reinterpret_cast<const char *>(string->start);
+    ptrdiff_t length = string->length;
+    ptrdiff_t capacity = string->capacity;
+#else
+    if (!is_valid_dereference(QueueItem(item, "?ptr?", string->ptr), 1))
+    {
+        // nullptr is NOT okay here
+        FAIL("invalid string pointer " << stl_sprintf("%p", string->ptr));
+        return;
+    }
+    if (!is_valid_dereference(QueueItem(item, "?hdr?", string->ptr - 1), sizeof(*string->ptr)))
+    {
+        return;
+    }
+    const char *start = reinterpret_cast<const char *>(string->ptr);
+    ptrdiff_t length = (string->ptr - 1)->length;
+    ptrdiff_t capacity = (string->ptr - 1)->capacity;
+#endif
+
+    if (length < 0)
+    {
+        FAIL("string length is negative (" << length << ")");
+    }
+    else if (capacity < 0)
+    {
+        FAIL("string capacity is negative (" << capacity << ")");
+    }
+    else if (capacity < length)
+    {
+        FAIL("string capacity (" << capacity << ") is less than length (" << length << ")");
+    }
+
+#ifndef WIN32
+    const std::string empty_string;
+    auto empty_string_data = reinterpret_cast<const string_data *>(&empty_string);
+    if (sizes && string->ptr != empty_string_data->ptr)
+    {
+        size_t allocated_size = get_allocated_size(QueueItem(item, "?hdr?", string->ptr - 1));
+        size_t expected_size = sizeof(*string->ptr) + capacity + 1;
+
+        if (!allocated_size)
+        {
+            FAIL("pointer does not appear to be a string");
+        }
+        else if (allocated_size != expected_size)
+        {
+            FAIL("allocated string data size (" << allocated_size << ") does not match expected size (" << expected_size << ")");
+        }
+    }
+#endif
+}
--- a/plugins/devel/check-structures-sanity/main.cpp
+++ b/plugins/devel/check-structures-sanity/main.cpp
@ -26,6 +26,9 @@ DFhackCExport command_result plugin_init(color_ostream &, std::vector<PluginComm
        "by default, check-structures-sanity reports invalid pointers, vectors, strings, and vtables."
    ));

+    known_types_by_size.clear();
+    build_size_table();
+
    return CR_OK;
 }

--- a/plugins/devel/check-structures-sanity/types.cpp
+++ b/plugins/devel/check-structures-sanity/types.cpp
@ -20,7 +20,14 @@ CheckedStructure::CheckedStructure() :
 }
 CheckedStructure::CheckedStructure(type_identity *identity, size_t count) :
    identity(identity),
-    count(count)
+    count(count),
+    eid(nullptr)
+{
+}
+CheckedStructure::CheckedStructure(type_identity *identity, size_t count, enum_identity *eid) :
+    identity(identity),
+    count(count),
+    eid(eid)
 {
 }
 CheckedStructure::CheckedStructure(const struct_field_info *field) :
@ -31,24 +38,8 @@ CheckedStructure::CheckedStructure(const struct_field_info *field) :
        UNEXPECTED;
    }

-    if (field->mode == struct_field_info::STATIC_ARRAY && field->eid)
-    {
-        UNEXPECTED;
-    }
-    else if (field->type && field->type->isContainer())
-    {
-        auto expected_eid = static_cast<container_identity *>(field->type)->getIndexEnumType();
-        if (field->eid != expected_eid)
-        {
-            UNEXPECTED;
-        }
-    }
-    else if (field->eid)
-    {
-        UNEXPECTED;
-    }
-
    identity = field->type;
+    eid = field->eid;
    switch (field->mode)
    {
        case struct_field_info::END:
@ -129,3 +120,15 @@ type_identity *Checker::wrap_in_pointer(type_identity *base)
 {
    RETURN_CACHED_WRAPPER(df::pointer_identity, base);
 }
+
+std::map<size_t, std::vector<std::string>> known_types_by_size;
+void build_size_table()
+{
+    for (auto & ident : compound_identity::getTopScope())
+    {
+        if (ident->byte_size() >= MIN_SIZE_FOR_SUGGEST)
+        {
+            known_types_by_size[ident->byte_size()].push_back(ident->getFullName());
+        }
+    }
+}
--- a/plugins/devel/check-structures-sanity/validate.cpp
+++ b/plugins/devel/check-structures-sanity/validate.cpp
@ -1,9 +1,8 @@
 #include "check-structures-sanity.h"

-bool Checker::is_valid_dereference(const QueueItem & item, const CheckedStructure & cs, bool quiet)
+bool Checker::is_valid_dereference(const QueueItem & item, const CheckedStructure & cs, size_t size, bool quiet)
 {
    auto base = const_cast<void *>(item.ptr);
-    auto size = cs.full_size();
    if (!base)
    {
        // cannot dereference null pointer, but not an error
@ -83,6 +82,47 @@ bool Checker::is_valid_dereference(const QueueItem & item, const CheckedStructur
 #undef FAIL_PTR
 }

+int64_t Checker::get_int_value(const QueueItem & item, type_identity *type, bool quiet)
+{
+    if (type == df::identity_traits<int32_t>::get())
+    {
+        return validate_and_dereference<int32_t>(item, quiet);
+    }
+    else if (type == df::identity_traits<uint32_t>::get())
+    {
+        return validate_and_dereference<uint32_t>(item, quiet);
+    }
+    else if (type == df::identity_traits<int16_t>::get())
+    {
+        return validate_and_dereference<int16_t>(item, quiet);
+    }
+    else if (type == df::identity_traits<uint16_t>::get())
+    {
+        return validate_and_dereference<uint16_t>(item, quiet);
+    }
+    else if (type == df::identity_traits<int64_t>::get())
+    {
+        return validate_and_dereference<int64_t>(item, quiet);
+    }
+    else if (type == df::identity_traits<uint64_t>::get())
+    {
+        return int64_t(validate_and_dereference<uint64_t>(item, quiet));
+    }
+    else if (type == df::identity_traits<int8_t>::get())
+    {
+        return validate_and_dereference<int8_t>(item, quiet);
+    }
+    else if (type == df::identity_traits<uint8_t>::get())
+    {
+        return validate_and_dereference<uint8_t>(item, quiet);
+    }
+    else
+    {
+        UNEXPECTED;
+        return 0;
+    }
+}
+
 const char *Checker::get_vtable_name(const QueueItem & item, const CheckedStructure & cs, bool quiet)
 {
    auto vtable = validate_and_dereference<const void *const*>(QueueItem(item, "?vtable?", item.ptr), quiet);
@ -235,3 +275,98 @@ std::pair<const void *, size_t> Checker::validate_vector_size(const QueueItem &

    return local_ok ? std::make_pair(start_ptr, ulength / item_size) : std::make_pair(nullptr, 0);
 }
+
+size_t Checker::get_allocated_size(const QueueItem & item)
+{
+    if (!sizes)
+    {
+        return 0;
+    }
+
+    uint32_t tag = *reinterpret_cast<const uint32_t *>(PTR_ADD(item.ptr, -8));
+    if (tag == 0xdfdf4ac8)
+    {
+        return *reinterpret_cast<const size_t *>(PTR_ADD(item.ptr, -16));
+    }
+
+    return 0;
+}
+
+#ifndef WIN32
+const std::string *Checker::validate_stl_string_pointer(const void *const* base)
+{
+    std::string empty_string;
+    if (*base == *reinterpret_cast<void **>(&empty_string))
+    {
+        return reinterpret_cast<const std::string *>(base);
+    }
+
+    const struct string_data_inner
+    {
+        size_t length;
+        size_t capacity;
+        int32_t refcount;
+    } *str_data = static_cast<const string_data_inner *>(*base) - 1;
+
+    uint32_t tag = *reinterpret_cast<const uint32_t *>(PTR_ADD(str_data, -8));
+    if (tag == 0xdfdf4ac8)
+    {
+        size_t allocated_size = *reinterpret_cast<const size_t *>(PTR_ADD(str_data, -16));
+        size_t expected_size = sizeof(*str_data) + str_data->capacity + 1;
+
+        if (allocated_size != expected_size)
+        {
+            return nullptr;
+        }
+    }
+    else
+    {
+        return nullptr;
+    }
+
+    if (str_data->capacity < str_data->length)
+    {
+        return nullptr;
+    }
+
+    const char *ptr = reinterpret_cast<const char *>(*base);
+    for (size_t i = 0; i < str_data->length; i++)
+    {
+        if (!*ptr++)
+        {
+            return nullptr;
+        }
+    }
+
+    if (*ptr++)
+    {
+        return nullptr;
+    }
+
+    return reinterpret_cast<const std::string *>(base);
+}
+#endif
+
+const char *const *Checker::get_enum_item_key(enum_identity *identity, int64_t value)
+{
+    size_t index;
+    if (auto cplx = identity->getComplex())
+    {
+        auto it = cplx->value_index_map.find(value);
+        if (it == cplx->value_index_map.cend())
+        {
+            return nullptr;
+        }
+        index = it->second;
+    }
+    else
+    {
+        if (value < identity->getFirstItem() || value > identity->getLastItem())
+        {
+            return nullptr;
+        }
+        index = value - identity->getFirstItem();
+    }
+
+    return &identity->getKeys()[index];
+}