NAME

sdb − symbol table types

SYNOPSIS

#include <sdb.h>

DESCRIPTION

Sdb.h defines some values of the n_type field of the symbol table of a.out files.  These are the types for permanent symbols (i.e. not local labels, etc.)  used by the 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. 

The n_value field of a symbol is relocated by the linker, ld(1) as an address within the appropriate segment. 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 n_type field has one of the following bits set:

/∗
∗ Other permanent symbol table entries have some of the N_STAB bits set.
∗ These are given in <sdb.h>
∗/
#defineN_STAB0xe0/∗ 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 symbolic debugger, sdb, uses the following n_type values:

#defineN_GSYM0x20/∗ global symbol: name,,0,type,0 ∗/
#defineN_FNAME0x22/∗ procedure name (f77 kludge): name,,0 ∗/
#defineN_FUN0x24/∗ procedure: name,,0,linenumber,address ∗/
#defineN_STSYM0x26/∗ static symbol: name,,0,type,address ∗/
#defineN_LCSYM0x28/∗ .lcomm symbol: name,,0,type,address ∗/
#defineN_RSYM0x40/∗ register sym: name,,0,type,register ∗/
#defineN_SLINE0x44/∗ src line: 0,,0,linenumber,address ∗/
#defineN_SSYM0x60/∗ structure elt: name,,0,type,struct_offset ∗/
#defineN_SO0x64/∗ source file name: name,,0,0,address ∗/
#defineN_LSYM0x80/∗ local sym: name,,0,type,offset ∗/
#defineN_SOL0x84/∗ #included file name: name,,0,0,address ∗/
#defineN_PSYM0xa0/∗ parameter: name,,0,type,offset ∗/
#defineN_ENTRY0xa4/∗ alternate entry: name,linenumber,address ∗/
#defineN_LBRAC0xc0/∗ left bracket: 0,,0,nesting level,address ∗/
#defineN_RBRAC0xe0/∗ right bracket: 0,,0,nesting level,address ∗/
#defineN_BCOMM0xe2/∗ begin common: name,, ∗/
#defineN_ECOMM0xe4/∗ end common: name,, ∗/
#defineN_ECOML0xe8/∗ end common (local name): ,,address ∗/
#defineN_LENG0xfe/∗ second stab entry with length information ∗/

where 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. Sdb uses the n_desc field to hold a type specifier in the form used by the Portable C Compiler, cc(1), in which a base type is qualified in the following structure:

struct desc {
shortbasic:4,
q1:2,
q2:2,
q3:2,
q4:2,
q5:2,
q6:2;
};

There are four qualifications, with q1 the most significant and q6 the least significant:

0none
1pointer
2function
3array

The sixteen basic types are assigned as follows:

0undefined
1function argument
2character
3short
4int
5long
6float
7double
8structure
9union
10enumeration
11member of enumeration
12unsigned character
13unsigned short
14unsigned int
15unsigned long

SEE ALSO

as(1), ld(1), a.out(5), stab(5)

BUGS

Sdb assumes that a symbol of type N_GSYM with name name is located at address _name.

More basic types are needed. 

4BSD