| 1 | |
| 2 | |
| 3 | |
| 4 | STAB(5) 1986 STAB(5) |
| 5 | |
| 6 | |
| 7 | |
| 8 | N\bNA\bAM\bME\bE |
| 9 | stab - symbol table types |
| 10 | |
| 11 | S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS |
| 12 | #\b#i\bin\bnc\bcl\blu\bud\bde\be <\b<s\bst\bta\bab\bb.\b.h\bh>\b> |
| 13 | |
| 14 | D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN |
| 15 | _\bS_\bt_\ba_\bb._\bh defines some values of the n_type field of the symbol |
| 16 | table of a.out files. These are the types for permanent |
| 17 | symbols (i.e. not local labels, etc.) used by the old |
| 18 | debugger _\bs_\bd_\bb and the Berkeley Pascal compiler _\bp_\bc(1). Symbol |
| 19 | table entries can be produced by the ._\bs_\bt_\ba_\bb_\bs assembler direc- |
| 20 | tive. This allows one to specify a double-quote delimited |
| 21 | name, a symbol type, one char and one short of information |
| 22 | about the symbol, and an unsigned long (usually an address). |
| 23 | To avoid having to produce an explicit label for the address |
| 24 | field, the ._\bs_\bt_\ba_\bb_\bd directive can be used to implicitly |
| 25 | address the current location. If no name is needed, symbol |
| 26 | table entries can be generated using the ._\bs_\bt_\ba_\bb_\bn directive. |
| 27 | The loader promises to preserve the order of symbol table |
| 28 | entries produced by ._\bs_\bt_\ba_\bb directives. As described in |
| 29 | _\ba._\bo_\bu_\bt(5), an element of the symbol table consists of the |
| 30 | following structure: |
| 31 | |
| 32 | /* |
| 33 | * Format of a symbol table entry. |
| 34 | */ |
| 35 | struct nlist { |
| 36 | union { |
| 37 | char *n_name; /* for use when in-core */ |
| 38 | long n_strx; /* index into file string table */ |
| 39 | } n_un; |
| 40 | unsigned char n_type; /* type flag */ |
| 41 | char n_other; /* unused */ |
| 42 | short n_desc; /* see struct desc, below */ |
| 43 | unsigned n_value; /* address or offset or line */ |
| 44 | }; |
| 45 | |
| 46 | The low bits of the n_type field are used to place a symbol |
| 47 | into at most one segment, according to the following masks, |
| 48 | defined in <_\ba._\bo_\bu_\bt._\bh>. A symbol can be in none of these seg- |
| 49 | ments by having none of these segment bits set. |
| 50 | |
| 51 | /* |
| 52 | * Simple values for n_type. |
| 53 | */ |
| 54 | #define N_UNDF 0x0 /* undefined */ |
| 55 | #define N_ABS 0x2 /* absolute */ |
| 56 | #define N_TEXT 0x4 /* text */ |
| 57 | #define N_DATA 0x6 /* data */ |
| 58 | #define N_BSS 0x8 /* bss */ |
| 59 | |
| 60 | |
| 61 | |
| 62 | |
| 63 | Printed 7/27/90 May 1 |
| 64 | |
| 65 | |
| 66 | |
| 67 | |
| 68 | |
| 69 | |
| 70 | STAB(5) 1986 STAB(5) |
| 71 | |
| 72 | |
| 73 | |
| 74 | #define N_EXT 01 /* external bit, or'ed in */ |
| 75 | |
| 76 | The n_value field of a symbol is relocated by the linker, |
| 77 | _\bl_\bd(1) as an address within the appropriate segment. N_value |
| 78 | fields of symbols not in any segment are unchanged by the |
| 79 | linker. In addition, the linker will discard certain sym- |
| 80 | bols, according to rules of its own, unless the n_type field |
| 81 | has one of the following bits set: |
| 82 | |
| 83 | /* |
| 84 | * Other permanent symbol table entries have some of the N_STAB bits set. |
| 85 | * These are given in <stab.h> |
| 86 | */ |
| 87 | #define N_STAB 0xe0/* if any of these bits set, don't discard */ |
| 88 | |
| 89 | |
| 90 | This allows up to 112 (7 * 16) symbol types, split between |
| 91 | the various segments. Some of these have already been |
| 92 | claimed. The old symbolic debugger, _\bs_\bd_\bb, uses the following |
| 93 | n_type values: |
| 94 | |
| 95 | #define N_GSYM 0x20 /* global symbol: name,,0,type,0 */ |
| 96 | #define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */ |
| 97 | #define N_FUN 0x24 /* procedure: name,,0,linenumber,address */ |
| 98 | #define N_STSYM 0x26 /* static symbol: name,,0,type,address */ |
| 99 | #define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */ |
| 100 | #define N_RSYM 0x40 /* register sym: name,,0,type,register */ |
| 101 | #define N_SLINE 0x44 /* src line: 0,,0,linenumber,address */ |
| 102 | #define N_SSYM 0x60 /* structure elt: name,,0,type,struct_offset */ |
| 103 | #define N_SO 0x64 /* source file name: name,,0,0,address */ |
| 104 | #define N_LSYM 0x80 /* local sym: name,,0,type,offset */ |
| 105 | #define N_SOL 0x84 /* #included file name: name,,0,0,address */ |
| 106 | #define N_PSYM 0xa0 /* parameter: name,,0,type,offset */ |
| 107 | #define N_ENTRY 0xa4 /* alternate entry: name,linenumber,address */ |
| 108 | #define N_LBRAC 0xc0 /* left bracket: 0,,0,nesting level,address */ |
| 109 | #define N_RBRAC 0xe0 /* right bracket: 0,,0,nesting level,address */ |
| 110 | #define N_BCOMM 0xe2 /* begin common: name,, */ |
| 111 | #define N_ECOMM 0xe4 /* end common: name,, */ |
| 112 | #define N_ECOML 0xe8 /* end common (local name): ,,address */ |
| 113 | #define N_LENG 0xfe /* second stab entry with length information */ |
| 114 | |
| 115 | where the comments give _\bs_\bd_\bb conventional use for ._\bs_\bt_\ba_\bbs and |
| 116 | the n_name, n_other, n_desc, and n_value fields of the given |
| 117 | n_type. _\bS_\bd_\bb uses the n_desc field to hold a type specifier |
| 118 | in the form used by the Portable C Compiler, _\bc_\bc(1); see the |
| 119 | header file _\bp_\bc_\bc._\bh for details on the format of these type |
| 120 | values. |
| 121 | |
| 122 | The Berkeley Pascal compiler, _\bp_\bc(1), uses the following |
| 123 | n_type value: |
| 124 | |
| 125 | |
| 126 | |
| 127 | |
| 128 | |
| 129 | Printed 7/27/90 May 2 |
| 130 | |
| 131 | |
| 132 | |
| 133 | |
| 134 | |
| 135 | |
| 136 | STAB(5) 1986 STAB(5) |
| 137 | |
| 138 | |
| 139 | |
| 140 | #define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */ |
| 141 | |
| 142 | and uses the following subtypes to do type checking across |
| 143 | separately compiled files: |
| 144 | 1 source file name |
| 145 | 2 included file name |
| 146 | 3 global label |
| 147 | 4 global constant |
| 148 | 5 global type |
| 149 | 6 global variable |
| 150 | 7 global function |
| 151 | 8 global procedure |
| 152 | 9 external function |
| 153 | 10 external procedure |
| 154 | 11 library variable |
| 155 | 12 library routine |
| 156 | |
| 157 | S\bSE\bEE\bE A\bAL\bLS\bSO\bO |
| 158 | as(1), ld(1), dbx(1), a.out(5) |
| 159 | |
| 160 | B\bBU\bUG\bGS\bS |
| 161 | More basic types are needed. |
| 162 | |
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| 194 | |
| 195 | Printed 7/27/90 May 3 |
| 196 | |
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| 198 | |