OSF

NAME

stab − Symbol table types

SYNOPSIS

#include <stab.h>

DESCRIPTION

The stab.h header file defines some values of the n_type field of the symbol table of a.out files.  These are the types for permanent symbols (that is, not local labels, etc.)  used by the old debugger sdb.  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.  An element of the symbol table consists of the following structure: /∗ SYMBOL INFORMATION ENTRY ∗ This is used for defined symbols, imports and stabs.  The type (kind) ∗ of the associated symbols load command determines which.  typedef struct symbol_info_t {
union{mo_offset_tsymbol_name;
mo_ptr_tsymbol_nameP;
      }si_name;
mo_short_tsi_package_index;
mo_short_tsi_type;
mo_short_tsi_flags;
mo_byte_tsi_reserved byte;
mo_byte_tsi_sc_type;
union{mo_addr_tdef_val;/∗ defined section, offset ∗/
mo_long_timp_val;/∗ index in import list ∗/
mo_long_tlit_val;/∗ literal value ∗/
mo_vm_addr_tabs_val;/∗ absolute value ∗/
      } si_value;
} symbol_info_t;

The low bits of the si_sc_type field are used to place a symbol into at most one segment, according to the following masks.  A symbol can be in none of these segments by having none of these segment bits set.  ∗ Simple values for si_sc_type. 
∗/ #defineN_UNDF0x0/∗ undefined ∗/
#defineN_ABS0x2/∗ absolute ∗/
#defineN_TEXT0x4/∗ text ∗/
#defineN_DATA0x6/∗ data ∗/
#defineN_BSS0x8/∗ bss ∗/
#defineN_EXT01/∗ external bit, or’ed in ∗/

The n_value field of a symbol is relocated by the linker, ld, as an address within the appropriate segment.  The n_value 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 si_sc_type field has one of the following bits set: #define N_STAB 0xe0 /∗ if any of these bits set, don’t discard ∗/

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

#define N_GSYM
0x20/∗ global symbol: name,,0,type,0 ∗/

#define N_FNAME
0x22/∗ procedurename(f77 kludge): name,,0 ∗/

#define N_FUN0x24/∗ procedure: name,,0,linenumber,address ∗/

#define N_STSYM
0x26/∗ static symbol: name,,0,type,address ∗/

#define N_LCSYM
0x28/∗ .lcomm symbol: name,,0,type,address ∗/

#define N_RSYM
0x40/∗ register sym: name,,0,type,register ∗/

#define N_SLINE
0x44/∗ src line: 0,,0,linenumber,address ∗/

#define N_SSYM
0x60/∗ structure elt: name,,0,type,struct_offset ∗/

#define N_SO0x64/∗ sourcefilename: name,,0,0,address ∗/

#define N_LSYM
0x80/∗ local sym: name,,0,type,offset ∗/

#define N_SOL0x84/∗ #includedfilename: name,,0,0,address ∗/

#define N_PSYM
0xa0/∗ parameter: name,,0,type,offset ∗/

#define N_ENTRY
0xa4/∗ alternate entry: name,,linenumber,address ∗/

#define N_LBRAC
0xc0/∗ left bracket: 0,,0,nestinglevel,address ∗/

#define N_RBRAC
0xe0/∗ right bracket: 0,,0,nestinglevel,address ∗/

#define N_BCOMM
0xe2/∗ begincommon: name,, ∗/

#define N_ECOMM
0xe4/∗ endcommon: name,, ∗/

#define N_ECOML
0xe8/∗ endcommon(local name): ,,address ∗/

#define N_LENG
0xfe/∗ secondstabentrywithlengthinformation ∗/

The comments give sdb conventional use for .stabs and the n_name, n_other, n_desc, and n_value fields of the given n_type.  The sdb debugger uses the n_desc field to hold a type specifier in the form used by the Portable C Compiler, cc. 

The Berkeley Pascal compiler, pc, uses the following si_sc_type value: #define  N_PC  0x30  /∗ global pascal symbol: name,,0,subtype,line ∗/

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

       •Source filename

       •Included filename

       •Global label

       •Global constant

       •Global type

       •Global variable

       •Global function

       •Global procedure

       •External function

       •External procedure

       •Library variable

       •"12" Library routine

RELATED INFORMATION

Commands: as(1), ld(1)