noft Manual (G06.27+, H06.03+, J06.03+)

noft Manual—528273-003
C-1
C
Native Object Code File Structure
The noft utility operates on native object code files, which have four main
components:
•
Headers of these types, which contain information about the structure and
components of the object code file:
°
File
°
Program
°
Section
•
Code and Data Segments
•
MDEBUG Section on page C-2
•
TANDEM_GINFO section, which contains information used by the operating
system to load loadfiles (for example, a lists of unresolved references and
procedure information for creating run-time stack traces)
Code and Data Segments
The code segments of an object code file contain the code for procedures and
subprocedures. In relinkable object code files, resident and nonresident procedures
are intermixed in the file. In loadfiles, resident and nonresident procedures are in
separate code segments.
The data segments of an object code file contain information, such as global variables
in pTAL and extern and static variables in C, that does not appear and disappear
with each invocation of a procedure or subprocedure. The compilers generate code
that uses the run-time stack to manage data that does appear and disappear.
Code and data segments are divided into sections. nld operates on sections for
linking, whereas the operating system operates on segments for loading programs into
virtual memory. Table C-1 lists the sections within each segment:
Table C-1. Loadfile Segments and Sections
Segments Sections
Code Nonresident Text
Resident Text
Read-only Data
Data Large Initialized Data
Small Initialized Data
Small Uninitialized Data
Large Uninitialized Data