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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)stab.5 8.1 (Berkeley) 6/5/93 29.\" $FreeBSD$ 30.\" 31.Dd June 10, 2010 32.Dt STAB 5 33.Os 34.Sh NAME 35.Nm stab 36.Nd symbol table types 37.Sh SYNOPSIS 38.In stab.h 39.Sh DESCRIPTION 40The file 41.In stab.h 42defines some of the symbol table 43.Fa n_type 44field values for a.out files. 45These are the types for permanent symbols (i.e., not local labels, etc.\&) 46used by the old debugger 47.Em sdb 48and the Berkeley Pascal compiler 49.Xr pc 1 . 50Symbol table entries can be produced by the 51.Pa .stabs 52assembler directive. 53This allows one to specify a double-quote delimited name, a symbol type, 54one char and one short of information about the symbol, and an unsigned 55long (usually an address). 56To avoid having to produce an explicit label for the address field, 57the 58.Pa .stabd 59directive can be used to implicitly address the current location. 60If no name is needed, symbol table entries can be generated using the 61.Pa .stabn 62directive. 63The loader promises to preserve the order of symbol table entries produced 64by 65.Pa .stab 66directives. 67As described in 68.Xr a.out 5 , 69an element of the symbol table 70consists of the following structure: 71.Bd -literal 72/* 73* Format of a symbol table entry. 74*/ 75 76struct nlist { 77 union { 78 const char *n_name; /* for use when in-core */ 79 long n_strx; /* index into file string table */ 80 } n_un; 81 unsigned char n_type; /* type flag */ 82 char n_other; /* unused */ 83 short n_desc; /* see struct desc, below */ 84 unsigned n_value; /* address or offset or line */ 85}; 86.Ed 87.Pp 88The low bits of the 89.Fa n_type 90field are used to place a symbol into 91at most one segment, according to 92the following masks, defined in 93.In a.out.h . 94A symbol can be in none of these segments by having none of these segment 95bits set. 96.Bd -literal 97/* 98* Simple values for n_type. 99*/ 100 101#define N_UNDF 0x0 /* undefined */ 102#define N_ABS 0x2 /* absolute */ 103#define N_TEXT 0x4 /* text */ 104#define N_DATA 0x6 /* data */ 105#define N_BSS 0x8 /* bss */ 106 107#define N_EXT 01 /* external bit, or'ed in */ 108.Ed 109.Pp 110The 111.Fa n_value 112field of a symbol is relocated by the linker, 113.Xr ld 1 114as an address within the appropriate segment. 115.Fa N_value 116fields of symbols not in any segment are unchanged by the linker. 117In addition, the linker will discard certain symbols, according to rules 118of its own, unless the 119.Fa n_type 120field has one of the following bits set: 121.Bd -literal 122/* 123* Other permanent symbol table entries have some of the N_STAB bits set. 124* These are given in <stab.h> 125*/ 126 127#define N_STAB 0xe0 /* if any of these bits set, don't discard */ 128.Ed 129.Pp 130This allows up to 112 (7 \(** 16) symbol types, split between the various 131segments. 132Some of these have already been claimed. 133The old symbolic debugger, 134.Em sdb , 135uses the following n_type values: 136.Bd -literal 137#define N_GSYM 0x20 /* global symbol: name,,0,type,0 */ 138#define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */ 139#define N_FUN 0x24 /* procedure: name,,0,linenumber,address */ 140#define N_STSYM 0x26 /* static symbol: name,,0,type,address */ 141#define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */ 142#define N_RSYM 0x40 /* register sym: name,,0,type,register */ 143#define N_SLINE 0x44 /* src line: 0,,0,linenumber,address */ 144#define N_SSYM 0x60 /* structure elt: name,,0,type,struct_offset */ 145#define N_SO 0x64 /* source file name: name,,0,0,address */ 146#define N_LSYM 0x80 /* local sym: name,,0,type,offset */ 147#define N_SOL 0x84 /* #included file name: name,,0,0,address */ 148#define N_PSYM 0xa0 /* parameter: name,,0,type,offset */ 149#define N_ENTRY 0xa4 /* alternate entry: name,linenumber,address */ 150#define N_LBRAC 0xc0 /* left bracket: 0,,0,nesting level,address */ 151#define N_RBRAC 0xe0 /* right bracket: 0,,0,nesting level,address */ 152#define N_BCOMM 0xe2 /* begin common: name,, */ 153#define N_ECOMM 0xe4 /* end common: name,, */ 154#define N_ECOML 0xe8 /* end common (local name): ,,address */ 155#define N_LENG 0xfe /* second stab entry with length information */ 156.Ed 157.Pp 158where the comments give 159.Em sdb 160conventional use for 161.Pa .stab 162.Fa s 163and the 164.Fa n_name , 165.Fa n_other , 166.Fa n_desc , 167and 168.Fa n_value 169fields 170of the given 171.Fa n_type . 172.Em Sdb 173uses the 174.Fa n_desc 175field to hold a type specifier in the form used 176by the Portable C Compiler, 177.Xr cc 1 ; 178see the header file 179.Pa pcc.h 180for details on the format of these type values. 181.Pp 182The Berkeley Pascal compiler, 183.Xr pc 1 , 184uses the following 185.Fa n_type 186value: 187.Bd -literal 188#define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */ 189.Ed 190.Pp 191and uses the following subtypes to do type checking across separately 192compiled files: 193.Bd -unfilled -offset indent 1941 source file name 1952 included file name 1963 global label 1974 global constant 1985 global type 1996 global variable 2007 global function 2018 global procedure 2029 external function 20310 external procedure 20411 library variable 20512 library routine 206.Ed 207.Sh SEE ALSO 208.Xr as 1 , 209.Xr ld 1 , 210.Xr a.out 5 211.Sh HISTORY 212The 213.Nm 214file appeared in 215.Bx 4.0 . 216.Sh BUGS 217More basic types are needed. 218