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33 .Nd symbol table types
39 defines some of the symbol table
41 field values for a.out files.
42 These are the types for permanent symbols (i.e., not local labels, etc.\&)
43 used by the old debugger
45 and the Berkeley Pascal compiler
47 Symbol table entries can be produced by the
50 This allows one to specify a double-quote delimited name, a symbol type,
51 one char and one short of information about the symbol, and an unsigned
52 long (usually an address).
53 To avoid having to produce an explicit label for the address field,
56 directive can be used to implicitly address the current location.
57 If no name is needed, symbol table entries can be generated using the
60 The loader promises to preserve the order of symbol table entries produced
66 an element of the symbol table
67 consists of the following structure:
70 * Format of a symbol table entry.
75 const char *n_name; /* for use when in-core */
76 long n_strx; /* index into file string table */
78 unsigned char n_type; /* type flag */
79 char n_other; /* unused */
80 short n_desc; /* see struct desc, below */
81 unsigned n_value; /* address or offset or line */
87 field are used to place a symbol into
88 at most one segment, according to
89 the following masks, defined in
91 A symbol can be in none of these segments by having none of these segment
95 * Simple values for n_type.
98 #define N_UNDF 0x0 /* undefined */
99 #define N_ABS 0x2 /* absolute */
100 #define N_TEXT 0x4 /* text */
101 #define N_DATA 0x6 /* data */
102 #define N_BSS 0x8 /* bss */
104 #define N_EXT 01 /* external bit, or'ed in */
109 field of a symbol is relocated by the linker,
111 as an address within the appropriate segment.
113 fields of symbols not in any segment are unchanged by the linker.
114 In addition, the linker will discard certain symbols, according to rules
115 of its own, unless the
117 field has one of the following bits set:
120 * Other permanent symbol table entries have some of the N_STAB bits set.
121 * These are given in <stab.h>
124 #define N_STAB 0xe0 /* if any of these bits set, don't discard */
127 This allows up to 112 (7 \(** 16) symbol types, split between the various
129 Some of these have already been claimed.
130 The old symbolic debugger,
132 uses the following n_type values:
134 #define N_GSYM 0x20 /* global symbol: name,,0,type,0 */
135 #define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */
136 #define N_FUN 0x24 /* procedure: name,,0,linenumber,address */
137 #define N_STSYM 0x26 /* static symbol: name,,0,type,address */
138 #define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */
139 #define N_RSYM 0x40 /* register sym: name,,0,type,register */
140 #define N_SLINE 0x44 /* src line: 0,,0,linenumber,address */
141 #define N_SSYM 0x60 /* structure elt: name,,0,type,struct_offset */
142 #define N_SO 0x64 /* source file name: name,,0,0,address */
143 #define N_LSYM 0x80 /* local sym: name,,0,type,offset */
144 #define N_SOL 0x84 /* #included file name: name,,0,0,address */
145 #define N_PSYM 0xa0 /* parameter: name,,0,type,offset */
146 #define N_ENTRY 0xa4 /* alternate entry: name,linenumber,address */
147 #define N_LBRAC 0xc0 /* left bracket: 0,,0,nesting level,address */
148 #define N_RBRAC 0xe0 /* right bracket: 0,,0,nesting level,address */
149 #define N_BCOMM 0xe2 /* begin common: name,, */
150 #define N_ECOMM 0xe4 /* end common: name,, */
151 #define N_ECOML 0xe8 /* end common (local name): ,,address */
152 #define N_LENG 0xfe /* second stab entry with length information */
155 where the comments give
172 field to hold a type specifier in the form used
173 by the Portable C Compiler,
177 for details on the format of these type values.
179 The Berkeley Pascal compiler,
185 #define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */
188 and uses the following subtypes to do type checking across separately
190 .Bd -unfilled -offset indent
200 10 external procedure
214 More basic types are needed.