1 =====================================
2 The PDB TPI and IPI Streams
3 =====================================
13 The PDB TPI Stream (Index 2) and IPI Stream (Index 4) contain information about
14 all types used in the program. It is organized as a :ref:`header <tpi_header>`
15 followed by a list of :doc:`CodeView Type Records <CodeViewTypes>`. Types are
16 referenced from various streams and records throughout the PDB by their
17 :ref:`type index <type_indices>`. In general, the sequence of type records
18 following the :ref:`header <tpi_header>` forms a topologically sorted DAG
19 (directed acyclic graph), which means that a type record B can only refer to
20 the type A if ``A.TypeIndex < B.TypeIndex``. While there are rare cases where
21 this property will not hold (particularly when dealing with object files
22 compiled with MASM), an implementation should try very hard to make this
23 property hold, as it means the entire type graph can be constructed in a single
27 Type records form a topologically sorted DAG (directed acyclic graph).
34 Recent versions of the PDB format (aka all versions covered by this document)
35 have 2 streams with identical layout, henceforth referred to as the TPI stream
36 and IPI stream. Subsequent contents of this document describing the on-disk
37 format apply equally whether it is for the TPI Stream or the IPI Stream. The
38 only difference between the two is in *which* CodeView records are allowed to
39 appear in each one, summarized by the following table:
41 +----------------------+---------------------+
42 | TPI Stream | IPI Stream |
43 +======================+=====================+
44 | LF_POINTER | LF_FUNC_ID |
45 +----------------------+---------------------+
46 | LF_MODIFIER | LF_MFUNC_ID |
47 +----------------------+---------------------+
48 | LF_PROCEDURE | LF_BUILDINFO |
49 +----------------------+---------------------+
50 | LF_MFUNCTION | LF_SUBSTR_LIST |
51 +----------------------+---------------------+
52 | LF_LABEL | LF_STRING_ID |
53 +----------------------+---------------------+
54 | LF_ARGLIST | LF_UDT_SRC_LINE |
55 +----------------------+---------------------+
56 | LF_FIELDLIST | LF_UDT_MOD_SRC_LINE |
57 +----------------------+---------------------+
59 +----------------------+---------------------+
61 +----------------------+---------------------+
63 +----------------------+---------------------+
65 +----------------------+---------------------+
67 +----------------------+---------------------+
69 +----------------------+---------------------+
71 +----------------------+---------------------+
73 +----------------------+---------------------+
75 +----------------------+---------------------+
77 +----------------------+---------------------+
79 +----------------------+---------------------+
81 +----------------------+---------------------+
83 +----------------------+---------------------+
85 The usage of these records is described in more detail in
86 :doc:`CodeView Type Records <CodeViewTypes>`.
93 A type index is a 32-bit integer that uniquely identifies a type inside of an
94 object file's ``.debug$T`` section or a PDB file's TPI or IPI stream. The
95 value of the type index for the first type record from the TPI stream is given
96 by the ``TypeIndexBegin`` member of the :ref:`TPI Stream Header <tpi_header>`
97 although in practice this value is always equal to 0x1000 (4096).
99 Any type index with a high bit set is considered to come from the IPI stream,
100 although this appears to be more of a hack, and LLVM does not generate type
101 indices of this nature. They can, however, be observed in Microsoft PDBs
102 occasionally, so one should be prepared to handle them. Note that having the
103 high bit set is not a necessary condition to determine whether a type index
104 comes from the IPI stream, it is only sufficient.
106 Once the high bit is cleared, any type index >= ``TypeIndexBegin`` is presumed
107 to come from the appropriate stream, and any type index less than this is a
108 bitmask which can be decomposed as follows:
112 .---------------------------.------.----------.
113 | Unused | Mode | Kind |
114 '---------------------------'------'----------'
118 - **Kind** - A value from the following enum:
122 enum class SimpleTypeKind : uint32_t {
123 None = 0x0000, // uncharacterized type (no type)
124 Void = 0x0003, // void
125 NotTranslated = 0x0007, // type not translated by cvpack
126 HResult = 0x0008, // OLE/COM HRESULT
128 SignedCharacter = 0x0010, // 8 bit signed
129 UnsignedCharacter = 0x0020, // 8 bit unsigned
130 NarrowCharacter = 0x0070, // really a char
131 WideCharacter = 0x0071, // wide char
132 Character16 = 0x007a, // char16_t
133 Character32 = 0x007b, // char32_t
135 SByte = 0x0068, // 8 bit signed int
136 Byte = 0x0069, // 8 bit unsigned int
137 Int16Short = 0x0011, // 16 bit signed
138 UInt16Short = 0x0021, // 16 bit unsigned
139 Int16 = 0x0072, // 16 bit signed int
140 UInt16 = 0x0073, // 16 bit unsigned int
141 Int32Long = 0x0012, // 32 bit signed
142 UInt32Long = 0x0022, // 32 bit unsigned
143 Int32 = 0x0074, // 32 bit signed int
144 UInt32 = 0x0075, // 32 bit unsigned int
145 Int64Quad = 0x0013, // 64 bit signed
146 UInt64Quad = 0x0023, // 64 bit unsigned
147 Int64 = 0x0076, // 64 bit signed int
148 UInt64 = 0x0077, // 64 bit unsigned int
149 Int128Oct = 0x0014, // 128 bit signed int
150 UInt128Oct = 0x0024, // 128 bit unsigned int
151 Int128 = 0x0078, // 128 bit signed int
152 UInt128 = 0x0079, // 128 bit unsigned int
154 Float16 = 0x0046, // 16 bit real
155 Float32 = 0x0040, // 32 bit real
156 Float32PartialPrecision = 0x0045, // 32 bit PP real
157 Float48 = 0x0044, // 48 bit real
158 Float64 = 0x0041, // 64 bit real
159 Float80 = 0x0042, // 80 bit real
160 Float128 = 0x0043, // 128 bit real
162 Complex16 = 0x0056, // 16 bit complex
163 Complex32 = 0x0050, // 32 bit complex
164 Complex32PartialPrecision = 0x0055, // 32 bit PP complex
165 Complex48 = 0x0054, // 48 bit complex
166 Complex64 = 0x0051, // 64 bit complex
167 Complex80 = 0x0052, // 80 bit complex
168 Complex128 = 0x0053, // 128 bit complex
170 Boolean8 = 0x0030, // 8 bit boolean
171 Boolean16 = 0x0031, // 16 bit boolean
172 Boolean32 = 0x0032, // 32 bit boolean
173 Boolean64 = 0x0033, // 64 bit boolean
174 Boolean128 = 0x0034, // 128 bit boolean
177 - **Mode** - A value from the following enum:
181 enum class SimpleTypeMode : uint32_t {
182 Direct = 0, // Not a pointer
183 NearPointer = 1, // Near pointer
184 FarPointer = 2, // Far pointer
185 HugePointer = 3, // Huge pointer
186 NearPointer32 = 4, // 32 bit near pointer
187 FarPointer32 = 5, // 32 bit far pointer
188 NearPointer64 = 6, // 64 bit near pointer
189 NearPointer128 = 7 // 128 bit near pointer
192 Note that for pointers, the bitness is represented in the mode. So a ``void*``
193 would have a type index with ``Mode=NearPointer32, Kind=Void`` if built for
194 32-bits but a type index with ``Mode=NearPointer64, Kind=Void`` if built for
197 By convention, the type index for ``std::nullptr_t`` is constructed the same
198 way as the type index for ``void*``, but using the bitless enumeration value
205 At offset 0 of the TPI Stream is a header with the following layout:
209 struct TpiStreamHeader {
212 uint32_t TypeIndexBegin;
213 uint32_t TypeIndexEnd;
214 uint32_t TypeRecordBytes;
216 uint16_t HashStreamIndex;
217 uint16_t HashAuxStreamIndex;
218 uint32_t HashKeySize;
219 uint32_t NumHashBuckets;
221 int32_t HashValueBufferOffset;
222 uint32_t HashValueBufferLength;
224 int32_t IndexOffsetBufferOffset;
225 uint32_t IndexOffsetBufferLength;
227 int32_t HashAdjBufferOffset;
228 uint32_t HashAdjBufferLength;
231 - **Version** - A value from the following enum.
235 enum class TpiStreamVersion : uint32_t {
243 Similar to the :doc:`PDB Stream <PdbStream>`, this value always appears to be
244 ``V80``, and no other values have been observed. It is assumed that should
245 another value be observed, the layout described by this document may not be
248 - **HeaderSize** - ``sizeof(TpiStreamHeader)``
250 - **TypeIndexBegin** - The numeric value of the type index representing the
251 first type record in the TPI stream. This is usually the value 0x1000 as
252 type indices lower than this are reserved (see :ref:`Type Indices
254 a discussion of reserved type indices).
256 - **TypeIndexEnd** - One greater than the numeric value of the type index
257 representing the last type record in the TPI stream. The total number of
258 type records in the TPI stream can be computed as ``TypeIndexEnd -
261 - **TypeRecordBytes** - The number of bytes of type record data following the
264 - **HashStreamIndex** - The index of a stream which contains a list of hashes
265 for every type record. This value may be -1, indicating that hash
266 information is not present. In practice a valid stream index is always
267 observed, so any producer implementation should be prepared to emit this
268 stream to ensure compatibility with tools which may expect it to be present.
270 - **HashAuxStreamIndex** - Presumably the index of a stream which contains a
271 separate hash table, although this has not been observed in practice and it's
272 unclear what it might be used for.
274 - **HashKeySize** - The size of a hash value (usually 4 bytes).
276 - **NumHashBuckets** - The number of buckets used to generate the hash values
277 in the aforementioned hash streams.
279 - **HashValueBufferOffset / HashValueBufferLength** - The offset and size within
280 the TPI Hash Stream of the list of hash values. It should be assumed that
281 there are either 0 hash values, or a number equal to the number of type
282 records in the TPI stream (``TypeIndexEnd - TypeEndBegin``). Thus, if
283 ``HashBufferLength`` is not equal to ``(TypeIndexEnd - TypeEndBegin) *
284 HashKeySize`` we can consider the PDB malformed.
286 - **IndexOffsetBufferOffset / IndexOffsetBufferLength** - The offset and size
287 within the TPI Hash Stream of the Type Index Offsets Buffer. This is a list
288 of pairs of uint32_t's where the first value is a :ref:`Type Index
289 <type_indices>` and the second value is the offset in the type record data of
290 the type with this index. This can be used to do a binary search followed by
291 a linear search to get O(log n) lookup by type index.
293 - **HashAdjBufferOffset / HashAdjBufferLength** - The offset and size within
294 the TPI hash stream of a serialized hash table whose keys are the hash values
295 in the hash value buffer and whose values are type indices. This appears to
296 be useful in incremental linking scenarios, so that if a type is modified an
297 entry can be created mapping the old hash value to the new type index so that
298 a PDB file consumer can always have the most up to date version of the type
299 without forcing the incremental linker to garbage collect and update
300 references that point to the old version to now point to the new version.
301 The layout of this hash table is described in :doc:`HashTable`.
305 CodeView Type Record List
306 =========================
307 Following the header, there are ``TypeRecordBytes`` bytes of data that
308 represent a variable length array of :doc:`CodeView type records
309 <CodeViewTypes>`. The number of such records (e.g. the length of the array)
310 can be determined by computing the value ``Header.TypeIndexEnd -
311 Header.TypeIndexBegin``.
313 O(log(n)) access is provided by way of the Type Index Offsets array (if
314 present) described previously.