Intel XENIX 286 Programmers Guide (86) - Tenox.tc

XENIX Programming cc: C Compiler
Using Modules, Segments, and Groups
"Module" is another name for an object file created by the C compiler. Every module
has a name, and the cc command uses this name in error messages if problems are
encountered during linking. The module name is usually the same as the source file's
name (without the ".c" or ".s" extension). You can change this name using the -NM
option. The option has the form
-NM name
where name can be any combination of letters and digits.
Changing a module's name is useful if the source file to be compiled is actually the
output of a program preprocessor and generator, such as lex or yacc.
A "segment" is a contiguous block of binary code produced by the C compiler. Every
module has two segments: a text segment containing the program instructions, and a
data segment containing the program data. Each segment in every module has a name.
This name is used by cc to define the order in which the segments of the program will
appear in memory when loaded for execution. Text segments having the same name are
loaded as a contiguous block of code. Data segments of the same name are also loaded
as contiguous blocks.
Text and data segment names are normally created by the C compiler. These default
names depend on the memory model chosen for the program. For example, in small
model programs the text segment is named " TEXT" and the data segment is named
"_DATA". These names are the same for all small model modules, so all segments from
all modules of a small model program are loaded as a contiguous block. In middle model
programs, each text segment has a different name. In large and huge model programs,
each text and data segment has a different name. The default text and data segment
names for middle, large, and huge model programs are given in the section "Segment and
Module Names" at the end of this chapter.
You can override the default names used by the C compiler (and override the default
loading order) by using the -NT and -ND options. These options set the names of the
text and data segments, in each module being compiled, to a given name. The options
have the form
and
-NT name
-ND name
where name is any combination of letters and digits. These options are useful in middle,
large, and huge model programs where there is no specific loading order. In these
programs, you can guarantee contiguous loading for two or more segments by giving
them the same name.
Note: Modules compiled with -ND option cannot call any system libraries.
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