1=====================================
2The Module Information Stream
3=====================================
4
5.. contents::
6   :local:
7
8.. _modi_stream_intro:
9
10Introduction
11============
12
13The Module Info Stream (henceforth referred to as the Modi stream) contains
14information about a single module (object file, import library, etc that
15contributes to the binary this PDB contains debug information about.  There
16is one modi stream for each module, and the mapping between modi stream index
17and module is contained in the :doc:`DBI Stream <DbiStream>`.  The modi stream
18for a single module contains line information for the compiland, as well as
19all CodeView information for the symbols defined in the compiland.  Finally,
20there is a "global refs" substream which is not well understood.
21
22.. _modi_stream_layout:
23
24Stream Layout
25=============
26
27A modi stream is laid out as follows:
28
29
30.. code-block:: c++
31
32  struct ModiStream {
33    uint32_t Signature;
34    uint8_t Symbols[SymbolSize-4];
35    uint8_t C11LineInfo[C11Size];
36    uint8_t C13LineInfo[C13Size];
37
38    uint32_t GlobalRefsSize;
39    uint8_t GlobalRefs[GlobalRefsSize];
40  };
41
42- **Signature** - Unknown.  In practice only the value of ``4`` has been
43  observed.  It is hypothesized that this value corresponds to the set of
44  ``CV_SIGNATURE_xx`` defines in ``cvinfo.h``, with the value of ``4``
45  meaning that this module has C13 line information (as opposed to C11 line
46  information).  A corollary of this is that we expect to only ever see
47  C13 line info, and that we do not understand the format of C11 line info.
48
49- **Symbols** - The :ref:`CodeView Symbol Substream <modi_symbol_substream>`.
50  ``SymbolSize`` is equal to the value of ``SymByteSize`` for the
51  corresponding module's entry in the :ref:`Module Info Substream
52  <dbi_mod_info_substream>` of the :doc:`DBI Stream <DbiStream>`.
53
54- **C11LineInfo** - A block containing CodeView line information in C11
55  format.  ``C11Size`` is equal to the value of ``C11ByteSize`` from the
56  :ref:`Module Info Substream <dbi_mod_info_substream>` of the
57  :doc:`DBI Stream <DbiStream>`.  If this value is ``0``, then C11 line
58  information is not present.  As mentioned previously, the format of
59  C11 line info is not understood and we assume all line in modern PDBs
60  to be in C13 format.
61
62- **C13LineInfo** - A block containing CodeView line information in C13
63  format.  ``C13Size`` is equal to the value of ``C13ByteSize`` from the
64  :ref:`Module Info Substream <dbi_mod_info_substream>` of the
65  :doc:`DBI Stream <DbiStream>`.  If this value is ``0``, then C13 line
66  information is not present.
67
68- **GlobalRefs** - The meaning of this substream is not understood.
69
70.. _modi_symbol_substream:
71
72The CodeView Symbol Substream
73=============================
74
75The CodeView Symbol Substream.  This is an array of variable length
76records describing the functions, variables, inlining information,
77and other symbols defined in the compiland.  The entire array consumes
78``SymbolSize-4`` bytes.  The format of a CodeView Symbol Record (and
79thusly, an array of CodeView Symbol Records) is described in
80:doc:`CodeViewSymbols`.
81