CodeView Type Records¶

Introduction ¶

This document describes the usage and serialization format of the various CodeView type records that LLVM understands. This document does not describe every single CodeView type record that is defined. In some cases, this is because the records are clearly deprecated and can only appear in very old software (e.g. the 16-bit types). On other cases, it is because the records have never been observed in practice. This could be because they are only generated for non-C++ code (e.g. Visual Basic, C#), or because they have been made obsolete by newer records, or any number of other reasons. However, the records we describe here should cover 99% of type records that one can expect to encounter when dealing with modern C++ toolchains.

Record Categories ¶

We can think of a sequence of CodeView type records as an array of variable length leaf records. Each such record describes its own length as part of a fixed-size header, as well as the kind of record it is. Leaf records are either padded to 4 bytes (if this type stream appears in a TPI/IPI stream of a PDB) or not padded at all (if this type stream appears in the .debug$T section of an object file). Padding is implemented by inserting a decreasing sequence of <_padding_records> that terminates with LF_PAD0.

The final category of record is a member record. One particular leaf type – LF_FIELDLIST – contains a series of embedded records. While the outer LF_FIELDLIST describes its length (like any other leaf record), the embedded records – called member records do not.

Leaf Records ¶

All leaf records begin with the following 4 byte prefix:

struct RecordHeader {
  uint16_t RecordLen;  // Record length, not including this 2 byte field.
  uint16_t RecordKind; // Record kind enum.
};

LF_POINTER (0x1002)¶

Usage: Describes a pointer to another type.

Layout:

.--------------------.-- +0
|    Referent Type   |
.--------------------.-- +4
|     Attributes     |
.--------------------.-- +8
|  Member Ptr Info   |       Only present if |Attributes| indicates this is a member pointer.
.--------------------.-- +E

Attributes is a bitfield with the following layout:

 .-----------------------------------------------------------------------------------------------------.
 |     Unused                   |  Flags  |       Size       |   Modifiers   |  Mode   |      Kind     |
 .-----------------------------------------------------------------------------------------------------.
 |                              |         |                  |               |         |               |
0x100                         +0x16     +0x13               +0xD            +0x8      +0x5            +0x0

where the various fields are defined by the following enums:

enum class PointerKind : uint8_t {
  Near16 = 0x00,                // 16 bit pointer
  Far16 = 0x01,                 // 16:16 far pointer
  Huge16 = 0x02,                // 16:16 huge pointer
  BasedOnSegment = 0x03,        // based on segment
  BasedOnValue = 0x04,          // based on value of base
  BasedOnSegmentValue = 0x05,   // based on segment value of base
  BasedOnAddress = 0x06,        // based on address of base
  BasedOnSegmentAddress = 0x07, // based on segment address of base
  BasedOnType = 0x08,           // based on type
  BasedOnSelf = 0x09,           // based on self
  Near32 = 0x0a,                // 32 bit pointer
  Far32 = 0x0b,                 // 16:32 pointer
  Near64 = 0x0c                 // 64 bit pointer
};
enum class PointerMode : uint8_t {
  Pointer = 0x00,                 // "normal" pointer
  LValueReference = 0x01,         // "old" reference
  PointerToDataMember = 0x02,     // pointer to data member
  PointerToMemberFunction = 0x03, // pointer to member function
  RValueReference = 0x04          // r-value reference
};
enum class PointerModifiers : uint8_t {
  None = 0x00,                    // "normal" pointer
  Flat32 = 0x01,                  // "flat" pointer
  Volatile = 0x02,                // pointer is marked volatile
  Const = 0x04,                   // pointer is marked const
  Unaligned = 0x08,               // pointer is marked unaligned
  Restrict = 0x10,                // pointer is marked restrict
};
enum class PointerFlags : uint8_t {
  WinRTSmartPointer = 0x01,       // pointer is a WinRT smart pointer
  LValueRefThisPointer = 0x02,    // pointer is a 'this' pointer of a member function with ref qualifier (e.g. void X::foo() &)
  RValueRefThisPointer = 0x04     // pointer is a 'this' pointer of a member function with ref qualifier (e.g. void X::foo() &&)
};

The Size field of the Attributes bitmask is a 1-byte value indicating the pointer size. For example, a void* would have a size of either 4 or 8 depending on the target architecture. On the other hand, if Mode indicates that this is a pointer to member function or pointer to data member, then the size can be any implementation defined number.

The Member Ptr Info field of the LF_POINTER record is only present if the attributes indicate that this is a pointer to member.

Note that “plain” pointers to primitive types are not represented by LF_POINTER records, they are indicated by special reserved TypeIndex values.