1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)stab.5 8.1 (Berkeley) 6/5/93 33.\" 34.Dd June 5, 1993 35.Dt STAB 5 36.Os BSD 4 37.Sh NAME 38.Nm stab 39.Nd symbol table types 40.Sh SYNOPSIS 41.Fd #include <stab.h> 42.Sh DESCRIPTION 43The file 44.Aq Pa stab.h 45defines some of the symbol table 46.Fa n_type 47field values for a.out files. 48These are the types for permanent symbols (i.e. not local labels, etc.) 49used by the old debugger 50.Em sdb 51and the Berkeley Pascal compiler 52.Xr pc 1 . 53Symbol table entries can be produced by the 54.Pa .stabs 55assembler directive. 56This allows one to specify a double-quote delimited name, a symbol type, 57one char and one short of information about the symbol, and an unsigned 58long (usually an address). 59To avoid having to produce an explicit label for the address field, 60the 61.Pa .stabd 62directive can be used to implicitly address the current location. 63If no name is needed, symbol table entries can be generated using the 64.Pa .stabn 65directive. 66The loader promises to preserve the order of symbol table entries produced 67by 68.Pa .stab 69directives. 70As described in 71.Xr a.out 5 , 72an element of the symbol table 73consists of the following structure: 74.Bd -literal 75/* 76* Format of a symbol table entry. 77*/ 78 79struct nlist { 80 union { 81 char *n_name; /* for use when in-core */ 82 long n_strx; /* index into file string table */ 83 } n_un; 84 unsigned char n_type; /* type flag */ 85 char n_other; /* unused */ 86 short n_desc; /* see struct desc, below */ 87 unsigned n_value; /* address or offset or line */ 88}; 89.Ed 90.Pp 91The low bits of the 92.Fa n_type 93field are used to place a symbol into 94at most one segment, according to 95the following masks, defined in 96.Aq Pa a.out.h . 97A symbol can be in none of these segments by having none of these segment 98bits set. 99.Bd -literal 100/* 101* Simple values for n_type. 102*/ 103 104#define N_UNDF 0x0 /* undefined */ 105#define N_ABS 0x2 /* absolute */ 106#define N_TEXT 0x4 /* text */ 107#define N_DATA 0x6 /* data */ 108#define N_BSS 0x8 /* bss */ 109 110#define N_EXT 01 /* external bit, or'ed in */ 111.Ed 112.Pp 113The 114.Fa n_value 115field of a symbol is relocated by the linker, 116.Xr ld 1 117as an address within the appropriate segment. 118.Fa N_value 119fields of symbols not in any segment are unchanged by the linker. 120In addition, the linker will discard certain symbols, according to rules 121of its own, unless the 122.Fa n_type 123field has one of the following bits set: 124.Bd -literal 125/* 126* Other permanent symbol table entries have some of the N_STAB bits set. 127* These are given in <stab.h> 128*/ 129 130#define N_STAB 0xe0 /* if any of these bits set, don't discard */ 131.Ed 132.Pp 133This allows up to 112 (7 \(** 16) symbol types, split between the various 134segments. 135Some of these have already been claimed. 136The old symbolic debugger, 137.Em sdb , 138uses the following n_type values: 139.Bd -literal 140#define N_GSYM 0x20 /* global symbol: name,,0,type,0 */ 141#define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */ 142#define N_FUN 0x24 /* procedure: name,,0,linenumber,address */ 143#define N_STSYM 0x26 /* static symbol: name,,0,type,address */ 144#define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */ 145#define N_RSYM 0x40 /* register sym: name,,0,type,register */ 146#define N_SLINE 0x44 /* src line: 0,,0,linenumber,address */ 147#define N_SSYM 0x60 /* structure elt: name,,0,type,struct_offset */ 148#define N_SO 0x64 /* source file name: name,,0,0,address */ 149#define N_LSYM 0x80 /* local sym: name,,0,type,offset */ 150#define N_SOL 0x84 /* #included file name: name,,0,0,address */ 151#define N_PSYM 0xa0 /* parameter: name,,0,type,offset */ 152#define N_ENTRY 0xa4 /* alternate entry: name,linenumber,address */ 153#define N_LBRAC 0xc0 /* left bracket: 0,,0,nesting level,address */ 154#define N_RBRAC 0xe0 /* right bracket: 0,,0,nesting level,address */ 155#define N_BCOMM 0xe2 /* begin common: name,, */ 156#define N_ECOMM 0xe4 /* end common: name,, */ 157#define N_ECOML 0xe8 /* end common (local name): ,,address */ 158#define N_LENG 0xfe /* second stab entry with length information */ 159.Ed 160.Pp 161where the comments give 162.Em sdb 163conventional use for 164.Pa .stab 165.Fa s 166and the 167.Fa n_name , 168.Fa n_other , 169.Fa n_desc , 170and 171.Fa n_value 172fields 173of the given 174.Fa n_type . 175.Em Sdb 176uses the 177.Fa n_desc 178field to hold a type specifier in the form used 179by the Portable C Compiler, 180.Xr cc 1 ; 181see the header file 182.Pa pcc.h 183for details on the format of these type values. 184.Pp 185The Berkeley Pascal compiler, 186.Xr pc 1 , 187uses the following 188.Fa n_type 189value: 190.Bd -literal 191#define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */ 192.Ed 193.Pp 194and uses the following subtypes to do type checking across separately 195compiled files: 196.Bd -unfilled -offset indent 1971 source file name 1982 included file name 1993 global label 2004 global constant 2015 global type 2026 global variable 2037 global function 2048 global procedure 2059 external function 20610 external procedure 20711 library variable 20812 library routine 209.Ed 210.Sh SEE ALSO 211.Xr as 1 , 212.Xr ld 1 , 213.Xr dbx 1 , 214.Xr a.out 5 215.Sh BUGS 216.Pp 217More basic types are needed. 218.Sh HISTORY 219The 220.Nm stab 221file appeared in 222.Bx 4.0 . 223