Debug Information Format

The debug information format encompasses a block of data which goes into the .exe file at a location dependent upon the executable file format. The version of the debug information is specified by a signature that is contained within the debug information. The signature has the format NBxx, where xx is the version number and have the following meanings.

NB00 Not supported

NB01 Not supported

NB02 Linked by a Microsoft LINK, version 5.10, or equivalent OEM linker

NB03 Not supported

NB04 Not supported

NB05 The signature emitted by LINK 5.20 and later linkers for a file before it has been packed.

NB06 Not supported.

NB07 This signature is used for Quick C for Windows 1.0 only.

NB08 The signature CodeView 4.00 through CodeView 4.05 uses for a file after it has been packed. CodeView 4.00 - 4.05 will not process a file that does not have this signature.

NB09 The signature for CodeView 4.10 for a file after it has been packed. CodeView 4.10 will not process a file that does not have this signature.

NB10 The signature for an executable with the debug information stored in a separate PDB file. Corresponds with the formats set forth in NB09 or NB11.

NB11 The signature for Visual C++ 5.0 debug information that has been packed and bonded to the executable. This includes all 32-bit type indices.

The method for finding the debug information depends upon the executable format.

PE Format:

For PE format executables, the base address lfaBase is found by examining the executable header.

executable header	Contains pointer to debug information
executable code + ...
NBxx	Signature at lfaBase
lfoDirectory	Offset of directory from base address (lfoDir)
Subsection tables	sstModule, sstType, sstLibraries, ...
.
.
.
Subsection Directory	At file offset lfaBase + lfoDir
other information

All other file offsets in the Symbol and Type OMF are relative to lfaBase. At the base address the signature is repeated, followed by the long displacement to the subsection directory (lfoDir). All subsections start on a long word boundary and are designed to maintain natural alignment internally in each subsection and within the subsection directory.