PRB: Type Indexes in .PDB Files Are Limited

• Microsoft Visual C++, 32-bit Edition, versions 4.0, 4.1, 4.2, 5.0

SYMPTOMS

When linking a debug version of your application, you may get the following warning:

   LINK : warning LNK4018: too many type indexes in PDB "filename",
   discarding subsequent type information

CAUSE

The number of type indexes in the Program Database File (.pdb file) for your project exceeded 64K for Visual C++ 4.x and 16M for later versions. This is a limitation of the debugging format in a .pdb file. The format uses a 16-bit field to store the number of types. This field was increased to 24 bits in Visual C++ 5.0.

RESOLUTION

To avoid this warning, use one or more of the following methods to decrease the number of type indexes in your .pdb file:

• Compile modules that you do not need to debug, without debugging information.
• Break your project into multiple Dynamic Link Libraries (DLLs). You can use subprojects in Developer Studio to build the new libraries.
• Use the compile time option /Yd. It will cause the type information for only those symbols that are referenced to be generated. This slows down builds somewhat but may lower the total number of symbols below the 64K limit.

STATUS

This behavior is by design.

MORE INFORMATION

You can review each object module to determine how many symbols it contains by using dumpbin /headers <file>.obj. The first section in the output tells how many symbols the object module contains.

With the introduction of Visual C++ 4.0, the size of the MFC libraries increased significantly and debugging information for the C run-time (CRT) libraries is now included in debug builds. These changes will increase the total number of type indexes in your project's .pdb file from earlier versions of Visual C++.