PRB: Not Enough Space for Environment

RESOLUTION

When the Windows loader loads an application, it also stores a copy of the MS-DOS environment strings (such as the PATH string, and so forth) in the application's DGROUP. In general, the space needed to store this environment table could be around 200 to 300 bytes, but it could vary depending on the environment variables in the system. The loader will try to allocate space for the environment table using LocalAlloc(), and this call will fail if there is not enough space in the local heap. In such a case, Windows automatically tries to expand the local heap by doing a Gloabal(Re)Alloc. Because the maximum size for the DGROUP is 64K, the GlobalAlloc will fail if the loader tries to grow the DGROUP beyond the 64K limit. This will happen when the size of the DGROUP is close to the limit of 64K and there is not enough space in the application's DGROUP for Windows to expand the local heap in it. In such a case, the application's DGROUP must be cleaned up to allow more space for the local heap. A few ways to do this are:

• Reduce the application's stack size using the STACKSIZE statement in the DEF file. A recommended stack size is between 5K and 10K. You can also determine exactly how much stack space your application needs and use that optimized value in your DEF file. For more information, query in the Microsoft Knowledge Base on the following words:

  stack pStackMin

• Move string constants from your DGROUP into string tables in a DEF file. Move large static arrays from your DGROUP to dynamically allocated memory using GlobalAlloc.
• If Microsoft C/C++ or Visual C++ compiler is being used, some of the data from the DGROUP can be moved into an extra data segment by using the /Gt compiler option (refer to pages 522-523 of the Microsoft C/C++ "Environment and Tools" manual). However, note that an application with multiple data segments will be restricted to only one instance. For more information on this problem, please query in the Microsoft Knowledge Base on the following words:

  large model C/C++