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