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|
.TH STAB 5
.CT 1 lib_obj
.SH NAME
stab \- symbol table types
.SH SYNOPSIS
.B "#include <stab.h>"
.SH DESCRIPTION
The include file
.L <stab.h>
defines some values of the
.L n_type
field of the symbol table of object files; see
.IR a.out (5).
These are the types for permanent symbols
used by the compilers
.IR cc (1)
and
.IR f77 (1)
and the debugger
.IR pi (9.1).
Symbol table entries are produced by assembler directives:
.TP \w'\f5.stabs\ \ \fP'u
.B .stabs
specifies a name in quotes \f5" "\fR, a symbol type
.RL ( n_type ),
one char
.RL ( n_other ),
one short
.RL ( n_desc),
and an unsigned long
.RL ( n_value ,
usually an address).
.PD 0
.TP
.B .stabd
the same, referring to the current location without an explicit
name.
.TP
.B .stabn
generates entries with no name.
.PD
.LP
The loader
.IR ld (1)
preserves the order of symbol table entries produced
by these directives.
.PP
The low bits of the
.L n_type
field place a symbol into
at most one segment, according to
the following masks, defined in
.BR <a.out.h> .
.PP
.EX
.ta \w'#define\ 'u +\w'N_FNAME\ 'u +\w'0x0\ \ \ 'u
#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 0x1 /* external bit, or'ed in */
.EE
.PP
The
.L n_value
field of a symbol is relocated by
.I ld
as an address within the appropriate segment,
or is unchanged for a symbol not in any segment.
In addition, the loader will discard certain symbols, according to rules
of its own, unless the
.L n_type
field has one of the following bits set:
.PP
.L
#define N_STAB 0xe0
.PP
This allows up to 112 symbol types, split among the various
segments.
Some of these have already been claimed.
Option
.B -g
of
.I cc
uses the following values, all 4 mod 16, for text symbols.
Comments show the pertinent fields of the
.B .stabs
directive.
.PP
.EX
.ta \w'#define\ 'u +\w'N_ECOMM\ 'u +\w'0x0\ \ \ 'u +\n(wwu
#define N_BFUN 0x24 /* procedure: name,,0,lineno,address */
#define N_FUN 0x24
#define N_NARGS 0x34 /* function call: ,,0,nbytes,address */
#define N_SLINE 0x44 /* src line: ,,0,lineno,address */
#define N_SO 0x64 /* source file: name,,0,lineno,address */
#define N_SOL 0x84 /* #include file: name,,0,lineno,address */
#define N_ESO 0x94 /* end source file: name,,0,lineno,address */
#define N_ENTRY 0xa4 /* alternate entry: name,,0,lineno,address */
#define N_RFUN 0xb4 /* return from function: ,,0,lineno,address */
#define N_LBRAC 0xc4 /* left bracket: ,,0,level,address */
#define N_RBRAC 0xd4 /* right bracket: ,,0,level,address */
#define N_EFUN 0xf4 /* end of function: name,,0,lineno,address */
.EE
.PP
These values, all 8 mod 16, are used for data symbols:
.PP
.EX
#define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */
#define N_ECOML 0xe8 /* end common (local name): ,,address */
.EE
.PP
And these for non-relocated symbols:
.PP
.EX
#define N_GSYM 0x20 /* global symbol: name,,0,type,0 */
#define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */
#define N_STFUN 0x32 /* static function: name,,0,type,0 */
#define N_RSYM 0x40 /* register sym: name,,0,type,register */
#define N_BSTR 0x5c /* begin structure: name,,0,type,length */
#define N_ESTR 0x5e /* end structure: name,,0,type,length */
#define N_SSYM 0x60 /* structure elt: name,,0,type,offset */
#define N_SFLD 0x70 /* structure field: name,,0,type,offset */
#define N_LSYM 0x80 /* local sym: name,,0,type,offset */
#define N_PSYM 0xa0 /* parameter: name,,0,type,offset */
#define N_BCOMM 0xe2 /* begin common: name,, */
#define N_ECOMM 0xe4 /* end common: name,, */
#define N_VER 0xf0 /* symbol table version number */
#define N_TYID 0xfa /* struct, union, or enum name */
#define N_DIM 0xfc /* dimension for arrays */
.EE
.PP
Field
.L n_desc
holds a type specifier in the form used by
.IR cc (1),
by up to 6 qualifiers, with
.B q1
most significant:
.PP
.EX
.ta \w'#define 'u +\w'short\ \ 'u
struct desc {
short q6:2, q5:2, q4:2, q3:2, q2:2, q1:2;
short basic:5;
};
.EE
.PP
The qualifiers are coded thus:
.2C
\f50\fR none
\f51\fR pointer
\f52\fR function
\f53\fR array
.1C
.PP
The basic types are coded thus:
.2C
\f50\fR undefined
\f51\fR function argument
\f52\fR character
\f53\fR short
\f54\fR int
\f55\fR long
\f56\fR float
\f57\fR double
\f58\fR structure
\f59\fR union
\f510\fR enumeration
\f511\fR member of enumeration
\f512\fR unsigned character
\f513\fR unsigned short
\f514\fR unsigned int
\f515\fR unsigned long
\f516\fR void
.1C
.PP
The Pascal compiler,
.IR pc (A),
uses the following
.L n_type
value:
.PP
.L
#define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */
.PP
and uses the following subtypes to do type checking across separately
compiled files:
.2C
\f51\fR source file name
\f52\fR included file name
\f53\fR global label
\f54\fR global constant
\f55\fR global type
\f56\fR global variable
\f57\fR global function
\f58\fR global procedure
\f59\fR external function
\f510\fR external procedure
.1C
.SH "SEE ALSO"
.IR a.out (5),
.IR pi (9.1),
.IR as (1),
.IR ld (1)
.SH BUGS
.PP
The loader's relocation conventions limit the number of useful
.LR n_type
values.
|
