plan9fox/sys/man/1/2l

.TH 2L 1 
.SH NAME
0l, 1l, 2l, 5l, 6l, 7l, 8l, kl, ql, vl \- loaders
.SH SYNOPSIS
.B 2l
[
.I option ...
]
[
.I file ...
]
.br
etc.
.SH DESCRIPTION
These commands
load the named
.I files
into executable files for the corresponding architectures; see
.IR 2c (1)
for the correspondence between an architecture and the character
.RB ( 1 ,
.RB 2 ,
etc.) that specifies it.
The files should be object files or libraries (archives of object files)
for the appropriate architecture.
Also, a name like
.BI -l ext
represents the library
.BI lib ext .a
in
.BR /$objtype/lib ,
where
.I objtype
is one of
.BR 68000 ,
etc. as listed in
.IR 2c (1).
The libraries must have tables of contents
(see
.IR ar (1)).
.PP
In practice, 
.B -l
options are rarely necessary as the header files for
the libraries cause their archives to be included automatically in the load
(see
.IR 2c (1)).
For example, any program that includes header file
.B libc.h
causes the loader
to search the C library
.BR /$objtype/lib/libc.a .
Also, the loader creates an undefined symbol
.B _main
(or
.B _mainp
if profiling is enabled) to force loading of the
startup linkage from the C library.
.PP
The order of search to resolve undefined symbols is to load all files and libraries
mentioned explicitly on the command line, and then to resolve remaining symbols
by searching in topological order
libraries mentioned in header files included by files already loaded.
When scanning such libraries, the algorithm is to scan each library repeatedly until
no new undefined symbols are picked up, then to start on the next library.  Thus if library
.I A
needs
.I B
which needs
.I A
again, it may be necessary to mention
.I A
explicitly so it will be read a second time.
.PP
The loader options are:
.TP 0.75i
.B -l
(As a bare option.)
Suppress the default loading of the startup linkage and libraries
specified by header files.
.TP
.BI -o " out"
Place output in file
.IR out .
Default is
.IB O .out\f1,
where
.I O
is the first letter of the loader name.
.TP
.B -p
Insert profiling code into the executable output; no special action is needed
during compilation or assembly.
.TP
.B -e
Insert (\fLe\fPmbedded) tracing code into the executable output; no special action is needed
during compilation or assembly.
The added code calls
.L _tracein
at function entries
and
.L _traceout
at function exits.
.TP
.B -s
Strip the symbol tables from the output file.
.TP
.B -a
Print the object code in assembly language, with addresses.
.TP
.B -v
Print debugging output that annotates the activities of the load.
.TP
.BI -M
.RI ( Kl
only) Generate instructions rather than calls to emulation routines
for multiply and divide.
.TP
.BI -E symbol
The entry point for the binary is
.I symbol
(default
.BR _main ;
.B _mainp
under
.BR -p ).
.TP
.BI -x " [ file ]"
Produce an export table in the executable.
The optional
.I file
restricts the exported symbols to those listed in the file.
See
.IR dynld (2).
.TP
.BI -u " [ file ]"
Produce an export table, import table
and a dynamic load section in the executable.
The optional
.I file
restricts the imported symbols to those listed in the file.
See
.IR dynld (2).
.TP
.B -t
(\c
.I 5l
and
.I vl
only)
Move strings into the text segment.
.TP
.BI -H n
Executable header is type
.IR n .
The meaning of the types is architecture-dependent; typically
type 1 is Plan 9 boot format and type 2 is the
regular Plan 9 format, the default.  These are reversed on the MIPS.
The Next boot format is 3.  Type 4 in
.I vl
creates a MIPS executable for an SGI Unix system.
.TP
.BI -T t
The text segment starts at address
.IR t .
.TP
.BI -D d
The data segment starts at address
.IR d .
.TP
.BI -R r
The text segment is rounded to a multiple of
.I r
(if
.I r
is nonzero).
.PP
The numbers in the above options can begin with
.L 0x
or
.L 0
to change the default base from decimal to hexadecimal or octal.
The defaults for the values depend on the compiler and the
header type.
.PP
The loaded image has several symbols inserted by the loader:
.B etext
is the address of the end of the text segment;
.B bdata
is the address of the beginning of the data segment;
.B edata
is the address of the end of the data segment;
and
.B end
is the address of the end of the bss segment, and of the program.
.SH FILES
.TF /$objtype/lib
.TP
.B /$objtype/lib
for
.BI -l lib
arguments.
.SH SOURCE
.B /sys/src/cmd/2l
etc.
.SH "SEE ALSO"
.IR 2c (1),
.IR 2a (1),
.IR ar (1),
.IR nm (1),
.IR db (1),
.IR prof (1)
.PP
Rob Pike,
``How to Use the Plan 9 C Compiler''
.SH BUGS
The list of loaders given above is only partial,
not all architectures are supported on all systems,
some have been retired and some
are provided by third parties.