85 lines
2.1 KiB
Text
85 lines
2.1 KiB
Text
.sp 1.5i
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.ft B
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Appendix B: Changes to the run time library
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.ft R
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.nh
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.sp
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Some minor changes in the run time library have been made concerning the
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external files (i.e. program arguments). The old compiler reserved
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space for the file structures of the external files in one \fBhol\fR block.
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In the new compiler, every file structure is placed in a separate \fBbss\fR
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block. This implies that the arguments with which \fI_ini\fR is called are
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slightly different. The second argument was the base of the \fBhol\fR block
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to relocate the buffer addresses, it is changed into an integer denoting the
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size of the array passed as third argument. The third argument was a pointer
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to an array of integers containing the description of external files, this
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argument is changed into a pointer to an array of pointers to file structures.
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The differences in the generated EM code for an arbitrary Pascal program are
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listed below (only the relevant parts are shown):
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.in +5m
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.nf
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\fBprogram\fR external_files(output,f);
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\fBvar\fR
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f : \fBfile of \fIsome-type\fR;
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.
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.
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\fBend\fR.
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.in -5m
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EM code generated by Pascal-VU:
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.in +5m
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.
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.
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hol 1088,-2147483648,0 ; space belonging to file structures of the program arguments
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.
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.
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.
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\&.2
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con 3, -1, 544, 0 \h'80u'; description of external files
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lxl 0
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lae .2
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lae 0 \h'146u'; base of hol block, to relocate buffer addresses
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lxa 0
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cal $_ini
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asp 16
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.
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.
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.in -5m
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EM code generated by our compiler:
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.in +5m
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.
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.
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f
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bss 540,0,0 \h'100u'; space belonging to file structure of program argument f
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output
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bss 540,0,0 \h'100u'; space belonging to file structure of standard output
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.
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.
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.
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\&.2
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con 0U4, output, f \h'50u'; the absence of standard input is denoted by a null pointer
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lxl 0
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lae .2
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loc 3 \h'144u'; denotes the size of the array of pointers to file structures
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lxa 0
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cal $_ini
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asp 16
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.
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.
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.in -5m
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.po
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The following files in the run time library have been changed:
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.in +1m
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pc_file.h
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hlt.c
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ini.c
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opn.c
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pentry.c
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pexit.c
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.in -1m
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.fi
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.bp
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.po
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