Finding Size of Program

• Microsoft Macro Assembler for MS-DOS, versions 1.25, 1.27, 3.0x, 4.0, 5.0, 5.1, and 6.0
• Microsoft Macro Assembler for OS/2, versions 5.1 and 6.0

The are programming situations in which it is necessary to determine the length of a program at run-time. For example, services (such as MS-DOS function 31H) need this information. Ordinarily, one could define a symbol at the end of a segment known to be loaded last; however, this does not work when linking with libraries because the libraries load after the .OBJ's.

The following is a method that be used to perform the equivolent operation when linking with library files that may rearange the segment order:

Begin your program with a list of declarations for all segments in your program. This will solve the load-order problem. However, if your segments are all named to classes and the order of the classes is all that is important, you only need one segment declaration per class.

Define a new and empty segment to be the last segment in your load image. Place your empty segment at the end of the list. The following is an example:

   ; Declarations to fix the load order. First, MYCODE
   ; and all segments of class CODE.

   MYCODE SEGMENT 'CODE'
   MYCODE ENDS

   ; Next MYDATA and all segments of class DATA

   MYDATA SEGMENT PUBLIC 'DATA'
   MYDATA ENDS

   ; Finally, LASTSEG.

   LASTSEG SEGMENT
   LASTSEG ENDS

If your segment declarations occur randomly throughout your source files and libraries, the solution is not as simple. The method to use is to make a new library, to be linked in last, that defines this last empty segment and a label in this segment. (You must have a reference to this label in some part of the program so the linker will pull in this library.)