1. COP 3402 Systems Programming
Dr. Ali Orooji
School of EECS University of Central Florida

2. Chapter 4 - MACRO PROCESSORS
Function
macro expansion; substitute macro bodies for
macro invocations
Source Program with macro invocations
Macro procesor
Source Program with macros expanded
assembler …

3. Two-Pass Macro Processor
process macro definitions
Pass 2
expand macro invocations
Problem
would not allow the body of one macro to contain
definitions of other macros

4. PMAC MACRO ...
C1MAC MACRO ...
...
MEND
C2MAC MACRO ...

5. One-Pass Macro Processor
. will process macro definitions and expand macro
invocations at the same time; will alternate between
macro definition and macro expansion
. the definition of a macro must come before any of its
invocations
Macro Processor Data Structures
definition table DEFTAB DEFTBL
- macro definitions are stored in this table
- references to parameters are converted to a
positional notation for efficiency in substituting
arguments

6. name table NAMTAB NAMTBL
- macro names are stored in this table along with
pointers to the beginning and end of definitions
in DEFTAB; serves as an index to DEFTAB
argument table ARGTAB ARGTBL
- used during the expansion of macro invocations
- arguments in a macro invocation are stored in this
table
Macro Processor Logic
pages of text
Figure 4.5 Algorithm for a one-pass macro processor

7. Machine-Independent Macro Processor Features
Section 4.2
Machine-Independent Macro Processor Features
Generation of Unique Labels
MAC MACRO
...
LBL
MEND
first macro expansion
AALBL
second macro expansion
ABLBL

8. Conditional Macro Expansion
IF ( Boolean expression )
...
ELSE
ENDIF
WHILE ( Boolean expression )
ENDW

9. Macro Processor Design Options
Section 4.3
Macro Processor Design Options
Recursive Macro Expansion
Problems with previous macro processor
- when a macro invokes another macro
ARGTAB is overwritten
- when the second macro finishes
EXPANDING is set to FALSE

10. Solution - if macro processor is written in a high-level
language that supports recursion, then there
won't be problems since the compiler saves the
previous values of variables on recursive calls
- if macro processor must be written in a
programming language that does not support
recursion, then the system programmer must
save the data values (this can be done using a
stack)

11. General-Purpose Macro Processors
not dependent on any particular programming
language; can be used with a variety of different
languages
Problems
- problems related to different programming
languages
. comments
. facilities for grouping
. tokens (identifiers, operators, ...)
- syntax used for macro definitions and
macro invocations

12. Macro Processing within Language Translators
previous macro processor: pre-processor
alternative: combining the macro processing
functions with the language translator
. line-by-line macro processor
. integrated macro processor