SYMS(4) SYMS(4)
NAME
syms - common object file symbol table format
SYNOPSIS
#include <syms.h>
DESCRIPTION
Common object files contain information to support symbolic
software testing [see sdb(1)]. Line number entries,
linenum(4), and extensive symbolic information permit
testing at the C source level. Every object file's symbol
table is organized as shown below.
File name 1.
Function 1.
Local symbols for function 1.
Function 2.
Local symbols for function 2.
...
Static externs for file 1.
File name 2.
Function 1.
Local symbols for function 1.
Function 2.
Local symbols for function 2.
...
Static externs for file 2.
...
Defined global symbols.
Undefined global symbols.
The entry for a symbol is a fixed-length structure. The
members of the structure hold the name (null padded), its
value, and other information. The C structure is given
below.
#define SYMNMLEN 8
#define FILNMLEN 14
Page 1 May 1989
SYMS(4) SYMS(4)
#define DIMNUM 4
struct syment
{
union /* all ways to get symbol name */
{
char _n_name[SYMNMLEN]; /* symbol name */
struct
{
long _n_zeroes; /* == 0L when in string table */
long _n_offset; /* location of name in table */
} _n_n;
char *_n_nptr[2]; /* allows overlaying */
} _n;
long n_value; /* value of symbol */
short n_scnum; /* section number */
unsigned short n_type; /* type and derived type */
char n_sclass; /* storage class */
char n_numaux; /* number of aux entries */
#if defined (m88k)
char n_pad1; /* pad to 4 byte multiple */
char n_pad2; /* pad to 4 byte multiple */
#endif
};
#define n_name _n._n_name
#define n_zeroes _n._n_n._n_zeroes
#define n_offset _n._n_n._n_offset
#define n_nptr _n._n_nptr[1]
Meaningful values and explanations for them are given in
both syms.h and Common Object File Format. Anyone who needs
to interpret the entries should seek more information in
these sources. Some symbols require more information than a
single entry; they are followed by auxiliary entries that
are the same size as a symbol entry. The format follows.
Page 2 May 1989
SYMS(4) SYMS(4)
union auxent
{
struct
{
long x_tagndx;
union
{
struct
{
unsigned short x_lnno;
unsigned short x_size;
} x_lnsz;
long x_fsize;
} x_misc;
union
{
struct
{
long x_lnnoptr;
long x_endndx;
} x_fcn;
struct
{
unsigned short x_dimen[DIMNUM];
} x_ary;
} x_fcnary;
unsigned short x_tvndx;
#if defined (m88k)
char r_pad1 ; /* pad to 4 byte multiple */
char r_pad2 ; /* pad to 4 byte multiple */
#endif
} x_sym;
struct
{
char x_fname[FILNMLEN];
} x_file;
struct
{
long x_scnlen;
unsigned short x_nreloc;
Page 3 May 1989
SYMS(4) SYMS(4)
unsigned short x_nlinno;
} x_scn;
struct
{
long x_tvfill;
unsigned short x_tvlen;
unsigned short x_tvran[2];
} x_tv;
};
Indexes of symbol table entries begin at zero.
SEE ALSO
sdb(1), a.out(4), linenum(4).
"Common Object File Format" in the Programming Guide.
WARNINGS
On machines on which ints are equivalent to longs, all longs
have their type changed to int. Thus the information about
which symbols are declared as longs and which, as ints, does
not show up in the symbol table.
Page 4 May 1989