222 lines
6.6 KiB
Groff
222 lines
6.6 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)stab.5 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd June 5, 1993
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.Dt STAB 5
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.Os
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.Sh NAME
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.Nm stab
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.Nd symbol table types
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.Sh SYNOPSIS
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.In stab.h
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.Sh DESCRIPTION
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The file
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.Aq Pa stab.h
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defines some of the symbol table
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.Fa n_type
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field values for a.out files.
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These are the types for permanent symbols (i.e. not local labels, etc.)
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used by the old debugger
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.Em sdb
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and the Berkeley Pascal compiler
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.Xr pc 1 .
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Symbol table entries can be produced by the
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.Pa .stabs
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assembler directive.
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This allows one to specify a double-quote delimited name, a symbol type,
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one char and one short of information about the symbol, and an unsigned
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long (usually an address).
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To avoid having to produce an explicit label for the address field,
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the
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.Pa .stabd
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directive can be used to implicitly address the current location.
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If no name is needed, symbol table entries can be generated using the
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.Pa .stabn
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directive.
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The loader promises to preserve the order of symbol table entries produced
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by
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.Pa .stab
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directives.
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As described in
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.Xr a.out 5 ,
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an element of the symbol table
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consists of the following structure:
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.Bd -literal
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/*
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* Format of a symbol table entry.
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*/
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struct nlist {
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union {
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char *n_name; /* for use when in-core */
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long n_strx; /* index into file string table */
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} n_un;
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unsigned char n_type; /* type flag */
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char n_other; /* unused */
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short n_desc; /* see struct desc, below */
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unsigned n_value; /* address or offset or line */
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};
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.Ed
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.Pp
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The low bits of the
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.Fa n_type
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field are used to place a symbol into
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at most one segment, according to
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the following masks, defined in
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.Aq Pa a.out.h .
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A symbol can be in none of these segments by having none of these segment
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bits set.
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.Bd -literal
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/*
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* Simple values for n_type.
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*/
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#define N_UNDF 0x0 /* undefined */
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#define N_ABS 0x2 /* absolute */
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#define N_TEXT 0x4 /* text */
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#define N_DATA 0x6 /* data */
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#define N_BSS 0x8 /* bss */
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#define N_EXT 01 /* external bit, or'ed in */
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.Ed
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.Pp
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The
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.Fa n_value
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field of a symbol is relocated by the linker,
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.Xr ld 1
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as an address within the appropriate segment.
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.Fa N_value
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fields of symbols not in any segment are unchanged by the linker.
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In addition, the linker will discard certain symbols, according to rules
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of its own, unless the
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.Fa n_type
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field has one of the following bits set:
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.Bd -literal
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/*
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* Other permanent symbol table entries have some of the N_STAB bits set.
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* These are given in <stab.h>
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*/
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#define N_STAB 0xe0 /* if any of these bits set, don't discard */
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.Ed
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.Pp
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This allows up to 112 (7 \(** 16) symbol types, split between the various
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segments.
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Some of these have already been claimed.
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The old symbolic debugger,
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.Em sdb ,
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uses the following n_type values:
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.Bd -literal
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#define N_GSYM 0x20 /* global symbol: name,,0,type,0 */
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#define N_FNAME 0x22 /* procedure name (f77 kludge): name,,0 */
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#define N_FUN 0x24 /* procedure: name,,0,linenumber,address */
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#define N_STSYM 0x26 /* static symbol: name,,0,type,address */
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#define N_LCSYM 0x28 /* .lcomm symbol: name,,0,type,address */
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#define N_RSYM 0x40 /* register sym: name,,0,type,register */
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#define N_SLINE 0x44 /* src line: 0,,0,linenumber,address */
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#define N_SSYM 0x60 /* structure elt: name,,0,type,struct_offset */
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#define N_SO 0x64 /* source file name: name,,0,0,address */
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#define N_LSYM 0x80 /* local sym: name,,0,type,offset */
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#define N_SOL 0x84 /* #included file name: name,,0,0,address */
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#define N_PSYM 0xa0 /* parameter: name,,0,type,offset */
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#define N_ENTRY 0xa4 /* alternate entry: name,linenumber,address */
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#define N_LBRAC 0xc0 /* left bracket: 0,,0,nesting level,address */
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#define N_RBRAC 0xe0 /* right bracket: 0,,0,nesting level,address */
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#define N_BCOMM 0xe2 /* begin common: name,, */
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#define N_ECOMM 0xe4 /* end common: name,, */
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#define N_ECOML 0xe8 /* end common (local name): ,,address */
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#define N_LENG 0xfe /* second stab entry with length information */
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.Ed
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.Pp
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where the comments give
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.Em sdb
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conventional use for
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.Pa .stab
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.Fa s
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and the
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.Fa n_name ,
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.Fa n_other ,
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.Fa n_desc ,
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and
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.Fa n_value
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fields
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of the given
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.Fa n_type .
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.Em Sdb
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uses the
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.Fa n_desc
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field to hold a type specifier in the form used
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by the Portable C Compiler,
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.Xr cc 1 ;
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see the header file
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.Pa pcc.h
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for details on the format of these type values.
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.Pp
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The Berkeley Pascal compiler,
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.Xr pc 1 ,
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uses the following
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.Fa n_type
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value:
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.Bd -literal
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#define N_PC 0x30 /* global pascal symbol: name,,0,subtype,line */
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.Ed
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.Pp
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and uses the following subtypes to do type checking across separately
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compiled files:
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.Bd -unfilled -offset indent
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1 source file name
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2 included file name
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3 global label
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4 global constant
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5 global type
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6 global variable
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7 global function
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8 global procedure
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9 external function
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10 external procedure
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11 library variable
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12 library routine
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.Ed
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.Sh SEE ALSO
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.Xr as 1 ,
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.Xr ld 1 ,
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.Xr a.out 5
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.Sh BUGS
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More basic types are needed.
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.Sh HISTORY
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The
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.Nm
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file appeared in
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.Bx 4.0 .
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