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1.1 root 1: Some Unix languages such as gcc and g++ produce assembler rather than object
2: code. This approach radically slows down the compiler and produces amazing
3: unneeded complexity, especially if debug information is to be placed on
4: object files.
5:
6: The compiler starts with type and line information in a format much like that
7: of the desired COFF output files. It must break this down into lines to ship
8: through the assembler, the assembler then must rebuild the information into
9: COFF format for output.
10:
11: In line with its function the Mark Williams assembler not only supports this
12: sillyness it documents it. (Not a Unix assembler notion). However error
13: checking of these is minamum and bad debug information can corrupt the
14: generated COFF output.
15:
16: This section must be read with a listing of coff.h for reference.
17:
18: .file "filename"
19: If used this should be the first statement in the file. It produces a
20: SYMENT of n_sclass = C_FILE and an AUXENT with ae_fname = filename. This
21: connects the object file to the original source file.
22:
23: .def symbolName
24: This initializes this SYMENT with n_name = symbolName. If there is a symbol
25: by that name on the assemblers internal symbol table it is marked to
26: prevent output to the symbol table, any RELOC references will point to
27: this table entry so its n_value had better end up correct. Because this
28: kind of code is assumed to be the result of a compiler we assume it is
29: right. The following commands upto and including .endef refer to this
30: SYMENT.
31:
32: .type number
33: This sets this SYMENT's n_type with number. If number indicates a function,
34: DT_FCN, An LINENO record is built pointing at this SYMENT.
35:
36: .val symbol or number
37: This sets this SYMENT's n_value and if it is a symbol it sets n_scnum
38: to the symbols section number.
39:
40: .scl number
41: This sets this SYMENT's n_sclass to number.
42:
43: .dim number [, number [, number [, number]]]
44: This sets up to 4 entries in an AUXENT's ae_dimen. It is used to describe
45: multi dimensioned arrays to COFF. Past 4 dimensional arrays the COFF specs
46: are admittedly buggy. One of the reasons that people are playing with other
47: output formats.
48:
49: .size n
50: This sets this AUXENT ae_size to n.
51:
52: .tag name
53: This scans backwards on the SYMENTs for a matching n_name. It points this
54: ae_tagndx to that names symbol number and that ae_endndx to the next symbol
55: number. A good example is a struct, It would start with a SYMENT of type
56: T_STRUCT, then there would be SYMENTs for its members. At the end there would
57: be a C_EOS (end of structure) with a tag that gets us back to the
58: symbol's name. .tag connects the forward and backward pointers.
59:
60: .line n
61: This sets the AUXENT's ae_lnno to n.
62:
63: .endef
64: This marks the end of a SYMENT started by .def. If the n_sclass == C_EFCN
65: (end of function) it builds the functions ae_fsize and ae_endndx and does
66: not output this syment. If any AUXENT fields were set an AUXENT record will
67: follow this SYMENT.
68:
69: .ln number
70: This builds a LINENO record with l_lnno = n and l_addr.l_paddr = the current
71: location.
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