ld.1

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 1 代码 · 共 566 行 · 第 1/2 页

.TH ld 1 RISC
.SH Name
ld, uld \- RISC link editor and ucode link editor
.SH Syntax
.BR ld [ 
.I options
] [
.I filename filename ...
]
.br
.BR uld [
.I options
] [
.I filename filename ...
]
.SH Description
The 
.PN ld
invokes the RISC link editor, which links RISC extended
.I coff
object files.  The archive format understood by
.PN ld
is the one created by the archiver
.PN ar .
.PP
The
.PN ld
editor combines several
object files into one, performs relocation, resolves external
symbols, and supports symbol table information for symbolic debugging.
In the simplest case, you specify the names of several object files as
arguments to the
.PN ld
command.
The 
.PN ld
command combines them, producing an object module that you can execute
or
use as input to a subsequent
.PN ld
command.
(In the latter case, you must specify the
.B \-r
option 
to preserve the relocation entries.) 
The command writes its output to a file named
.PN a.out .
By default, this file is executable if no errors occurred during the load.
.PP
The
.PN ld
command concatenates object files in the order in which you specify them.
The entry point of the output is the
beginning of the text segment (unless you specify the \fB\-e\fP option).
.PP
The
.PN uld
command combines several ucode object files and libraries into one ucode
object file. The command hides external symbols for better optimizations by
subsequent compiler passes.  The
.PN uld
command uses the symbol tables of
.I coff
object files loaded with ucode object files to determine what
external symbols not to hide. You can specify that the
.PN uld
command not hide external symbols by creating a file that describes those
symbols.  
.PP
The link editors
.PN ld
and
.PN uld
accept object files targeted for either Big Endian or Little Endian byte 
ordering with their headers and
symbolic tables in any byte ordering.  However 
.PN ld
and
.PN uld
are faster if the headers and symbolic tables have the byte ordering of the
machine that they are running on.  The default byte ordering of the headers
and symbolic tables is the target byte ordering of the output object file.
For nonrelocatable object files, the default byte ordering of the headers
and symbolic tables cannot be changed.
.PP
If you specify that you want to link a library, the
.PN ld
and 
.PN uld
commands search the library exactly once
at the point it is encountered in the argument list.
The library (archive) symbol table (see
.MS ar 1 )
is a hash table that
.PN ld
and
.PN uld 
search to resolve external references. 
The commands load only those routines that define unresolved external
references. 
The order of the routines in the library is
unimportant.
.PP
By default, the
.PN ld
and 
.PN uld
commands search for libraries in the
.PN /lib , 
.PN /usr/lib, 
and 
.PN /usr/local/lib 
directories.  
In some cases, the target byte ordering of the object files
.PN ld
or 
.PN uld
is loading is the opposite of the byte ordering of the machine on which
the link editor is executing. When this case occurs, the link editor
changes the default directories it searches for libraries. If the object
file's byte ordering is Big Endian and the machine's byte ordering is
Little Endian (Digital products), the link editor searches the
.PN /libeb ,
.PN /usr/libeb ,
and
.PN /usr/local/libeb
directories, by default. Conversely, if the object file's byte ordering
is Little Endian and the machine's byte ordering is Big Endian, the
editor searches the
.PN /libel ,
.PN /usr/libel ,
and
.PN /usr/local/libel
directories, by default.
.PP
The following symbols are reserved; do not define them:
etext, edata, end, _ftext, _fdata, _fbss, _gp,
\_procedure_table,
\_procedure_table_size, and
\_procedure_string_table.
These loader defined symbols, if referred to, have their values set as
described in 
.MS end 3 .
.SH Options
You can use the following options on both the
.PN ld
and
.PN uld 
command lines.
If you specify an option that the command does not use, the command
ignores that option.
.PP
You can specify the options described in this section on the
.PN cc
command line. To do so, prepend a 
.B k
to the option. When you prepend a 
.B k ,
the
.PN cc
command ignores the option and passes it to the link editor. The link
editor ignores the prepended
.B k
and processes the option normally. Therefore, the 
.B \-kA
option has the same effect as specifying
.B \-A .
.TP 15
.BI \-A " file"
Link to allow incremental loading.  The link editor performs the link
process so that the 
resulting object can be read into an already executing program.
.IP
The 
.I file
argument
is the name of an object file. The link editor defines additional symbols using
the symbol table in that file. This argument must appear on the command
line before any other object file.
.IP
During an incremental load, the link editor loads only newly linked material 
into the text and
data portions of 
.BR a.out .
However, the new symbol table reflects
every symbol defined before and after the incremental load.
.IP
You can use the 
.B \-T
option to cause the link editor to assume
that the
newly linked segment starts at the specified address,
which must be a correct multiple for the resulting object type.
The default resulting object type is an OMAGIC file. The default
starting address of the text is the value of the end symbol rounded to
SCNROUND as defined in the include file
.PN <scnhdr.h>.
By default, when the newly linked segment is read into an already executing program
the initial value of the break must also be rounded.
.IP
All objects except the argument to the
.B \-A
option must be compiled with the
.BI \-G " 0"
option. Using the 
.B \-A
option sets 
.BI \-G " 0"
for linking.
.IP
For jump instructions to operate correctly, the beginning and ending
points of the instruction 
must be in the same 256 megabyte segment. Thus, it is invalid to use the
default address of a ZMAGIC file as the base file and allow the newly linked text to
start at the value of the end symbol.
.IP
To solve this problem,
use the
.B \-D
option when you create the base file.  Using this option ensures that
the text and data will be in the same 256 megabyte segment.
Alternatively, use the
.B \-N
option, which places the data section immediately following the text
section.
.TP 15
.BI \-B " num"
Set the bss segment origin.  The argument
.I num
is a hexadecimal address.
You can use this option only if the final object is an OMAGIC file.
.TP 15
.BI \-B string
Append
.I string
to the library name created for the
.BI \-l x
or
.BI \-kl x
options. When searching for a library, the link editor first appends
.I string
to the library name. If the link editor cannot find a library of that
name, it searches for the library name without 
.I string.
.TP 15
.B \-b
Do not merge the symbolic information entries for the same file into one entry
for that file.  Use this option when the symbolic information
from the same file appears differently in any of the objects to be linked.  This
situation can occur when object files are compiled, by means of conditional 
compilation, with an apparently different version of an include file.
.TP 15
.B \-bestGnum
Calculate the best number to use as an argument to the
.B \-G 
option. Use this option when you are 
compiling and linking the files that will produce the objects you want
to link with
.BR \-G .
Using too large a number with the
.B \-G 
option may cause the 
global pointer data area to overflow; using too small a number may
reduce your program's execution speed.
.TP 15
.B \-count 
.ns
.TP 15
.B \-countall
.ns
.TP 15
.B \-nocount 
Count (or do not count) the specified objects as able to be recompiled when
calculating the best number to use as an argument to the
.B \-G
option.
By default, the
.B \-bestGnum
option assumes you can recompile everything with the 
.B \-G 
option. If you cannot recompile certain object files or libraries
(because, for example, you have no sources for them), use these
options to tell the link editor to take this into account in calculating