m4: Sync with FreeBSD.
[dragonfly.git] / usr.bin / m4 / NOTES
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1m4 - macro processor
2
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3PD m4 is based on the macro tool distributed with the software
4tools (VOS) package, and described in the "SOFTWARE TOOLS" and
5"SOFTWARE TOOLS IN PASCAL" books. It has been expanded to include
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6most of the command set of SysV m4, the standard UN*X macro processor.
7
8Since both PD m4 and UN*X m4 are based on SOFTWARE TOOLS macro,
9there may be certain implementation similarities between
10the two. The PD m4 was produced without ANY references to m4
11sources.
12
13written by: Ozan S. Yigit
14
15References:
16
17 Software Tools distribution: macro
18
19 Kernighan, Brian W. and P. J. Plauger, SOFTWARE
20 TOOLS IN PASCAL, Addison-Wesley, Mass. 1981
21
22 Kernighan, Brian W. and P. J. Plauger, SOFTWARE
23 TOOLS, Addison-Wesley, Mass. 1976
24
25 Kernighan, Brian W. and Dennis M. Ritchie,
26 THE M4 MACRO PROCESSOR, Unix Programmer's Manual,
27 Seventh Edition, Vol. 2, Bell Telephone Labs, 1979
28
29 System V man page for M4
30
31
32Implementation Notes:
33
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34[1] PD m4 uses a different (and simpler) stack mechanism than the one
35 described in Software Tools and Software Tools in Pascal books.
36 The triple stack thing is replaced with a single stack containing
37 the call frames and the arguments. Each frame is back-linked to a
38 previous stack frame, which enables us to rewind the stack after
39 each nested call is completed. Each argument is a character pointer
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40 to the beginning of the argument string within the string space.
41 The only exceptions to this are (*) arg 0 and arg 1, which are
42 the macro definition and macro name strings, stored dynamically
43 for the hash table.
44
45 . .
46 | . | <-- sp | . |
47 +-------+ +-----+
48 | arg 3 ------------------------------->| str |
49 +-------+ | . |
50 | arg 2 --------------+ .
51 +-------+ |
52 * | | |
53 +-------+ | +-----+
54 | plev | <-- fp +---------------->| str |
55 +-------+ | . |
56 | type | .
57 +-------+
58 | prcf -----------+ plev: paren level
59 +-------+ | type: call type
60 | . | | prcf: prev. call frame
61 . |
62 +-------+ |
63 | <----------+
64 +-------+