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stab(4)
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_t symbol_name;
	       mo_ptr_t symbol_nameP;
	 } si_name;
	 mo_short_t   si_package_index;
	 mo_short_t   si_type;
	 mo_short_t   si_flags;
	 mo_byte_t	   si_reserved byte;
	 mo_byte_t	   si_sc_type;
	 union {mo_addr_t      def_val;	       /* defined section, offset */
	 mo_long_t     imp_val; /* index in import list */
	 mo_long_t     lit_val; /* literal value */
	 mo_vm_addr_t abs_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. */
       #define N_UNDF  0x0     /* undefined */
       #define N_ABS   0x2     /* absolute */
       #define N_TEXT  0x4     /* text */
       #define N_DATA  0x6     /* data */
       #define N_BSS   0x8     /* bss */
       #define N_EXT   01	 /* 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_FUN 0x24 /* 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_SO 0x64 /* sourcefilename: name,,0,0,address */

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

  #define N_SOL 0x84 /* #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

SEE ALSO
  Commands: as(1), ld(1)

Index for Section 4

Alphabetical listing for S

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