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authorCem Keylan <cem@ckyln.com>2020-10-16 17:47:01 +0300
committerCem Keylan <cem@ckyln.com>2020-10-16 17:47:01 +0300
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tree1f479b2714e127835db7f33a3bfed4c38c52f883 /usr.bin/m4/NOTES
parente2abcdca396661cbe0ae2ddb13d5c2b85682c13a (diff)
downloadotools-5d69c6a2661bba0a22f3ecfd517e2e9767a38346.tar.gz
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+m4 - macro processor
+
+PD m4 is based on the macro tool distributed with the software
+tools (VOS) package, and described in the "SOFTWARE TOOLS" and
+"SOFTWARE TOOLS IN PASCAL" books. It has been expanded to include
+most of the command set of SysV m4, the standard UN*X macro processor.
+
+Since both PD m4 and UN*X m4 are based on SOFTWARE TOOLS macro,
+there may be certain implementation similarities between
+the two. The PD m4 was produced without ANY references to m4
+sources.
+
+written by: Ozan S. Yigit
+
+References:
+
+ Software Tools distribution: macro
+
+ Kernighan, Brian W. and P. J. Plauger, SOFTWARE
+ TOOLS IN PASCAL, Addison-Wesley, Mass. 1981
+
+ Kernighan, Brian W. and P. J. Plauger, SOFTWARE
+ TOOLS, Addison-Wesley, Mass. 1976
+
+ Kernighan, Brian W. and Dennis M. Ritchie,
+ THE M4 MACRO PROCESSOR, Unix Programmer's Manual,
+ Seventh Edition, Vol. 2, Bell Telephone Labs, 1979
+
+ System V man page for M4
+
+
+Implementation Notes:
+
+[1] PD m4 uses a different (and simpler) stack mechanism than the one
+ described in Software Tools and Software Tools in Pascal books.
+ The triple stack thing is replaced with a single stack containing
+ the call frames and the arguments. Each frame is back-linked to a
+ previous stack frame, which enables us to rewind the stack after
+ each nested call is completed. Each argument is a character pointer
+ to the beginning of the argument string within the string space.
+ The only exceptions to this are (*) arg 0 and arg 1, which are
+ the macro definition and macro name strings, stored dynamically
+ for the hash table.
+
+ . .
+ | . | <-- sp | . |
+ +-------+ +-----+
+ | arg 3 ------------------------------->| str |
+ +-------+ | . |
+ | arg 2 --------------+ .
+ +-------+ |
+ * | | |
+ +-------+ | +-----+
+ | plev | <-- fp +---------------->| str |
+ +-------+ | . |
+ | type | .
+ +-------+
+ | prcf -----------+ plev: paren level
+ +-------+ | type: call type
+ | . | | prcf: prev. call frame
+ . |
+ +-------+ |
+ | <----------+
+ +-------+