STAB(5)                     BSD File Formats Manual                    STAB(5)

NAME
     stab -- symbol table types

SYNOPSIS
     ##include <>

DESCRIPTION
     The file  defines some of the symbol table ntype field values
     for Mach-O a.out files.  These are the types for permanent symbols (i.e.
     not local labels, etc.)  used by the old debugger sdb and the Berkeley
     Pascal compiler pc(1).  Symbol table entries can be produced by the
     .stabs assembler directive.  This allows one to specify a double-quote
     delimited name, a symbol type, one char and one short of information
     about the symbol, and an unsigned long (usually an address).  To avoid
     having to produce an explicit label for the address field, the .stabd
     directive can be used to implicitly address the current location.  If no
     name is needed, symbol table entries can be generated using the .stabn
     directive.  The loader promises to preserve the order of symbol table
     entries produced by .stab directives.  As described in comments in  an element of the symbol table consists of the following
     structure:

     /*
     * Format of a symbol table entry.
     */

     struct nlist {
             union {
                     char    *nname;        /* for use when in-core */
                     long    nstrx;         /* index into file string table */
             } nun;
             unsigned char   ntype;         /* type flag */
             char            nsect;         /* section number or NOSECT */
             short           ndesc;         /* see struct desc, below */
             unsigned        nvalue;        /* address or offset or line */
     };

     The low bits of the ntype field are used for the symbol type, according
     to the following masks, defined in .  A symbol can be of none
     these types by having none of these bits set.

     /*
     * Simple values for ntype.
     */

     #define NUNDF  0x0     /* undefined */
     #define NABS   0x2     /* absolute */
     #define NSECT  0xe     /* defined in section number nsect */

     #define NEXT   01      /* external bit, or'ed in */

     The nvalue field of a symbol is relocated by the linker, ld(1) as an
     address within the appropriate section for NSECT types based on the.
     Nvalue fields of symbols not in any segment are unchanged by the linker.
     In addition, the linker will discard certain symbols, according to rules
     of its own, unless the ntype field has one of the following bits set:

     /*
     * Other permanent symbol table entries have some of the NSTAB bits set.
     * These are given in 
     */

     #define NSTAB  0xe0    /* if any of these bits set, don't discard */

     This allows up to 112 (7 * 16) symbol types, split between the various
     symbol types.  Some of these have already been claimed.  The old symbolic
     debugger, sdb, uses the following ntype values:

     #define NGSYM  0x20    /* global symbol: name,,NOSECT,type,0 */
     #define NFNAME 0x22    /* procedure name (f77 kludge): name,,NOSECT */
     #define NFUN   0x24    /* procedure: name,,nsect,linenumber,address */
     #define NSTSYM 0x26    /* static symbol: name,,nsect,type,address */
     #define NLCSYM 0x28    /* .lcomm symbol: name,,nsect,type,address */
     #define NBNSYM 0x2e    /* begin nsect sym: 0,,nsect,0,address */
     #define NRSYM  0x40    /* register sym: name,,NOSECT,type,register */
     #define NSLINE 0x44    /* src line: 0,,nsect,linenumber,address */
     #define NENSYM 0x4e    /* end nsect sym: 0,,nsect,0,address */
     #define NSYM  0x60    /* structure elt: name,,NOSECT,type,structoffset */
     #define NSO    0x64    /* source file name: name,,nsect,0,address */
     #define NLSYM  0x80    /* local sym: name,,NOSECT,type,offset */
     #define NBINCL 0x82    /* include file beginning: name,,NOSECT,0,sum */
     #define NSOL   0x84    /* #included file name: name,,nsect,0,address */
     #define NPSYM  0xa0    /* parameter: name,,NOSECT,type,offset */
     #define NEINCL 0xa2    /* include file end: name,,NOSECT,0,0 */
     #define NENTRY 0xa4    /* alternate entry: name,,nsect,linenumber,address */
     #define NLBRAC 0xc0    /* left bracket: 0,,NOSECT,nesting level,address */
     #define NEXCL  0xc2    /* deleted include file: name,,NOSECT,0,sum */
     #define NRBRAC 0xe0    /* right bracket: 0,,NOSECT,nesting level,address */
     #define NBCOM 0xe2    /* begin common: name,,NOSECT,0,0 */
     #define NECOM 0xe4    /* end common: name,,nsect,0,0 */
     #define NECOML 0xe8    /* end common (local name): 0,,nsect,0,address */
     #define NLENG  0xfe    /* second stab entry with length information */

     where the comments give sdb conventional use for .stab s and the nname,
     nsect, ndesc, and nvalue fields of the given ntype.  Sdb uses the
     ndesc field to hold a type specifier in the form used by the Portable C
     Compiler, cc(1); see the header file pcc.h for details on the format of
     these type values.

     The Berkeley Pascal compiler, pc(1), uses the following ntype value:

     #define NPC    0x30    /* global pascal symbol: name,,NOSECT,subtype,line */

     and uses the following subtypes to do type checking across separately
     compiled files:

           1       source file name
           2       included file name
           3       global label
           4       global constant
           5       global type
           6       global variable
           7       global function
           8       global procedure
           9       external function
           10      external procedure
           11      library variable
           12      library routine

SEE ALSO
     as(1), ld(1), dbx(1), Mach-O(5)

BUGS
     More basic types are needed.

HISTORY
     The stab file appeared in 4.0BSD.

Darwin                         November 16, 2001                        Darwin