LF_BUILDINFO (0x1603)

Describes the environment and arguments to an invocation of a tool or compiler.

struct BuildInfo {
    ItemId cwd;
    ItemId build_tool;
    ItemId source_file;
    ItemId pdb_file;
    ItemId args;
};

Unlike most records, this record can be truncated after any field. The record can also be seen as a single array of type ItemId, with meanings assigned to each fixed array index.

Each field in BuildInfo is an ItemId that refers to an LF_STRING_ID or LF_SUBSTR_LIST record. See LF_SUBSTR_LIST for details on how string records are concatenated to form whole strings.

Each module stream may contain at most one S_BUILDINFO record. If present, the S_BUILDINFO contains the ItemId that points to the LF_BUILDINFO record in the IPI Stream. This is the only way to associate a module with an LF_BUILDINFO record.

• cwd - The current directory when the tool ran.

• build_tool - The path to the tool executable, e.g. d:\...\cl.exe.

• source_file - The primary source file that was passed to the tool. For C/C++, this is usually the source file that was passed on the command-line to the compiler. For Rust, this is the path to the root module source file.

• pdb_file - The path to the compiler PDB (not linker PDB), if applicable. For MSVC, this will only be non-empty if the compiler was invoked with /Zi or /ZI. See: Debug Information Format

• args - Command-line arguments that were passed to the tool.

TODO: It appears that MSVC replaces response file arguments (e.g. @d:\foo\args.rsp) with their contents, when generating the string records that LF_BUILDINFO points to. However, we should confirm (or disprove) this.

Fields in LF_BUILDINFO may be absent entirely (because the structure is too small to contain the field), may have a value of 0, or may point to an empty LF_STRING_ID record. Decoders should make very few assumptions about the information in this record.

Example

00000000 : 05 00 4c 41 00 00 ed 10 00 00 4d 41 00 00 4e 41 : ..LA......MA..NA
00000010 : 00 00 54 41 00 00 f2 f1                         : ..TA....

• cwd = LF_STRING_ID : D:\\dw.main\\.build\\Windows\\x64\\src\\Binding\\FontBindingShared
• tool = LF_STRING_ID : C:\\Program Files\\Microsoft Visual Studio\\2022\\Enterprise\\VC\\Tools\\MSVC\\14.36.32532\\bin\\HostX64\\x64\\CL.exe
• source_file = LF_STRING_ID : D:\\dw.main\\src\\Binding\\FontBindingShared\\FontBindingShared.cpp
• pdb = LF_STRING_ID : D:\\dw.main\\.build\\Windows\\x64\\src\\Binding\\FontBindingShared\\Debug\\FontBinding.pdb
• args = LF_STRING_ID : -external:I\"C:\\Program Files (x86)\\Windows Kits\\10\\Include\\10.0.19041.0\\cppwinrt\" -external:I\"C:\\Program Files (x86)\\Windows Kits\\NETFXSDK\\4.8\\Include\\um\" -X

Example

First, we find an LF_BUILDINFO record. The record begins at offset 0x1d82.

00001d80 : 00 f1 1a 00 03 16 05 00 ec 10 00 00 ed 10 00 00 : ................
00001d90 : ef 10 00 00 f0 10 00 00 fc 10 00 00 f2 f1 1a 00 : ................
00001da0 : 03 16 05 00 ec 10 00 00 ed 10 00 00 ee 10 00 00 : ................

The num_strings field is 5. Each of the string IDs decodes as follows:

Index	Name	Value
0	cwd	0x10ec
1	tool	0x10ed
2	source	0x10ef
3	pdb	0x10f0
4	args	0x10fc

The record ends with two alignment padding bytes (F2 F1).

To decode the strings, we subtract the type_index_begin value from the IPI Stream Header from the string ID, then count records from the start of the IPI record stream. The type_index_begin value is typically 0x1000; no other value has been observed.

For cwd at ItemID 0x10ec, we find this LF_STRING_ID record:

00001230 : 00 00 20 01 00 00 02 00 32 00 05 16 00 00 00 00 : .. .....2.......
00001240 : 44 3a 5c 64 77 2e 6d 61 69 6e 5c 2e 62 75 69 6c : D:\dw.main\.buil
00001250 : 64 5c 57 69 6e 64 6f 77 73 5c 78 36 34 5c 73 72 : d\Windows\x64\sr
00001260 : 63 5c 43 6f 6d 6d 6f 6e 00 f3 f2 f1 72 00 05 16 : c\Common....r...

Note that the record offset (0x1238) cannot be directly computed from the ItemID (0x10ec). It is necessary to sequentially scan records from the beginning of the IPI Stream. Note also that ItemId values are subject to the same "backward-pointing" constraint as TypeIndex values in the TPI; an ItemId in a record R must point to an ItemId that is numerically less than the ItemId of R itself.

This gives the current working directory of the tool when it was executed, which is D:\dw.main\.build\Windows\x64\src\Common in this example.

Let's also examine the args ItemId, whose value is 0x10FC. In this case, 0x10FC points to this LF_STRING_ID record:

00001cd0 : 00 00 f9 10 00 00 fa 10 00 00 a6 00 05 16 fb 10 : ................
00001ce0 : 00 00 20 2d 65 78 74 65 72 6e 61 6c 3a 49 22 43 : .. -external:I"C
00001cf0 : 3a 5c 50 72 6f 67 72 61 6d 20 46 69 6c 65 73 20 : :\Program Files 
00001d00 : 28 78 38 36 29 5c 57 69 6e 64 6f 77 73 20 4b 69 : (x86)\Windows Ki
00001d10 : 74 73 5c 31 30 5c 49 6e 63 6c 75 64 65 5c 31 30 : ts\10\Include\10
00001d20 : 2e 30 2e 31 39 30 34 31 2e 30 5c 63 70 70 77 69 : .0.19041.0\cppwi
00001d30 : 6e 72 74 22 20 2d 65 78 74 65 72 6e 61 6c 3a 49 : nrt" -external:I
00001d40 : 22 43 3a 5c 50 72 6f 67 72 61 6d 20 46 69 6c 65 : "C:\Program File
00001d50 : 73 20 28 78 38 36 29 5c 57 69 6e 64 6f 77 73 20 : s (x86)\Windows 
00001d60 : 4b 69 74 73 5c 4e 45 54 46 58 53 44 4b 5c 34 2e : Kits\NETFXSDK\4.
00001d70 : 38 5c 49 6e 63 6c 75 64 65 5c 75 6d 22 20 2d 58 : 8\Include\um" -X
00001d80 : 00 f1 1a 00 03 16 05 00 ec 10 00 00 ed 10 00 00 : ................

The command-line arguments many C/C++ compiler invocations is quite long. In this case, the LF_STRING_ID field has a non-zero "substring pointer" field, which points to 0x10FB. This is the 0x10FB record, which starts at 0x1CAE:

00001ca0 : 34 31 2e 30 5c 77 69 6e 72 74 22 00 f2 f1 2a 00 : 41.0\winrt"...*.
00001cb0 : 04 16 09 00 00 00 f1 10 00 00 f2 10 00 00 f3 10 : ................
00001cc0 : 00 00 f4 10 00 00 f6 10 00 00 f7 10 00 00 f8 10 : ................
00001cd0 : 00 00 f9 10 00 00 fa 10 00 00 a6 00 05 16 fb 10 : ................

This record is LF_SUBSTR_LIST (0x1604), and contains a list of substrings. To reconstruct the full command-line string, it is necessary to traverse these substring pointers.