1.\" $NetBSD: stab.5,v 1.15 2017/07/03 21:30:59 wiz Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)stab.5 8.1 (Berkeley) 6/5/93 31.\" 32.Dd June 5, 1993 33.Dt STAB 5 34.Os 35.Sh NAME 36.Nm stab 37.Nd symbol table types 38.Sh SYNOPSIS 39.In stab.h 40.Sh DESCRIPTION 41The file 42.In stab.h 43defines some of the symbol table 44.Fa n_type 45field values for a.out files. 46These are the types for permanent symbols (i.e. not local labels, etc.) 47used by the old debugger 48.Em sdb 49and the Berkeley Pascal compiler 50.Ic pc . 51Symbol table entries can be produced by the 52.Pa .stabs 53assembler directive. 54This allows one to specify a double-quote delimited name, a symbol type, 55one char and one short of information about the symbol, and an unsigned 56long (usually an address). 57To avoid having to produce an explicit label for the address field, 58the 59.Pa .stabd 60directive can be used to implicitly address the current location. 61If no name is needed, symbol table entries can be generated using the 62.Pa .stabn 63directive. 64The loader promises to preserve the order of symbol table entries produced 65by 66.Pa .stab 67directives. 68As described in 69.Xr a.out 5 , 70an element of the symbol table 71consists of the following structure: 72.Bd -literal 73/* 74* Format of a symbol table entry. 75*/ 76 77struct nlist { 78 union { 79 char *n_name; /* for use when in-core */ 80 long n_strx; /* index into file string table */ 81 } n_un; 82 unsigned char n_type; /* type flag */ 83 char n_other; /* unused */ 84 short n_desc; /* see struct desc, below */ 85 unsigned n_value; /* address or offset or line */ 86}; 87.Ed 88.Pp 89The low bits of the 90.Fa n_type 91field are used to place a symbol into 92at most one segment, according to 93the following masks, defined in 94.In a.out.h . 95A symbol can be in none of these segments by having none of these segment 96bits set. 97.Bd -literal 98/* 99* Simple values for n_type. 100*/ 101 102#define N_UNDF 0x0 /* undefined */ 103#define N_ABS 0x2 /* absolute */ 104#define N_TEXT 0x4 /* text */ 105#define N_DATA 0x6 /* data */ 106#define N_BSS 0x8 /* bss */ 107 108#define N_EXT 01 /* external bit, or'ed in */ 109.Ed 110.Pp 111The 112.Fa n_value 113field of a symbol is relocated by the linker, 114.Xr ld 1 115as an address within the appropriate segment. 116.Fa n_value 117fields of symbols not in any segment are unchanged by the linker. 118In addition, the linker will discard certain symbols, according to rules 119of its own, unless the 120.Fa n_type 121field has one of the following bits set: 122.Bd -literal 123/* 124* Other permanent symbol table entries have some of the N_STAB bits set. 125* These are given in <stab.h> 126*/ 127 128#define N_STAB 0xe0 /* if any of these bits set, don't discard */ 129.Ed 130.Pp 131This allows up to 112 (7 \(** 16) symbol types, split between the various 132segments. 133Some of these have already been claimed. 134The old symbolic debugger, 135.Em sdb , 136uses the following n_type values: 137.Bd -literal 138#define N_GSYM 0x20 /* global symbol: name,,0,type,0 */ 139#define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */ 140#define N_FUN 0x24 /* procedure: name,,0,linenumber,address */ 141#define N_STSYM 0x26 /* static symbol: name,,0,type,address */ 142#define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */ 143#define N_RSYM 0x40 /* register sym: name,,0,type,register */ 144#define N_SLINE 0x44 /* src line: 0,,0,linenumber,address */ 145#define N_SSYM 0x60 /* structure elt: name,,0,type,struct_offset */ 146#define N_SO 0x64 /* source file name: name,,0,0,address */ 147#define N_LSYM 0x80 /* local sym: name,,0,type,offset */ 148#define N_SOL 0x84 /* #included file name: name,,0,0,address */ 149#define N_PSYM 0xa0 /* parameter: name,,0,type,offset */ 150#define N_ENTRY 0xa4 /* alternative entry: name,linenumber,address */ 151#define N_LBRAC 0xc0 /* left bracket: 0,,0,nesting level,address */ 152#define N_RBRAC 0xe0 /* right bracket: 0,,0,nesting level,address */ 153#define N_BCOMM 0xe2 /* begin common: name,, */ 154#define N_ECOMM 0xe4 /* end common: name,, */ 155#define N_ECOML 0xe8 /* end common (local name): ,,address */ 156#define N_LENG 0xfe /* second stab entry with length information */ 157.Ed 158.Pp 159where the comments give 160.Em sdb 161conventional use for 162.Pa .stab 163.Fa s 164and the 165.Fa n_name , 166.Fa n_other , 167.Fa n_desc , 168and 169.Fa n_value 170fields 171of the given 172.Fa n_type . 173.Em Sdb 174uses the 175.Fa n_desc 176field to hold a type specifier in the form used 177by the Portable C Compiler, 178.Xr cc 1 ; 179see the header file 180.Pa pcc.h 181for details on the format of these type values. 182.Pp 183The Berkeley Pascal compiler, 184.Ic pc , 185uses the following 186.Fa n_type 187value: 188.Bd -literal 189#define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */ 190.Ed 191.Pp 192and uses the following subtypes to do type checking across separately 193compiled files: 194.Bd -unfilled -offset indent 1951 source file name 1962 included file name 1973 global label 1984 global constant 1995 global type 2006 global variable 2017 global function 2028 global procedure 2039 external function 20410 external procedure 20511 library variable 20612 library routine 207.Ed 208.Sh SEE ALSO 209.Xr as 1 , 210.Xr gdb 1 , 211.Xr ld 1 , 212.Xr a.out 5 213.Sh HISTORY 214The 215.Nm stab 216file appeared in 217.Bx 4.0 . 218.Sh BUGS 219More basic types are needed. 220