2C(10.1) 2C(10.1)
NAME
0c, 1c, 2c, 5c, 6c, 7c, 8c, kc, qc, vc - C compilers
SYNOPSIS
2c [ option ... ] [ file ... ]
etc.
DESCRIPTION
These commands compile the named C files into object files
for the corresponding architecture. Associated with each
compiler is a string objtype, for example
0c spim Little-endian MIPS
1c 68000 Motorola MC68000
2c 68020 Motorola MC68020
5c arm ARM 7500
6c amd64 AMD64 extension to x86
7c alpha Digital Alpha APX
8c 386 Intel i386, i486, Pentium, etc.
kc sparc Sun SPARC
qc power Power PC,
vc mips big-endian MIPS 3000 family
Let the first letter of the compiler name be O= 0, 1, 2, 5,
6, 7, 8, k, q, or v. The output object files end in .O.
The letter is also the prefix of related programs: Oa is the
assembler, Ol is the loader.
Plan 9 conventionally sets the $objtype environment variable
to the objtype string appropriate to the current machine's
type. Plan 9 also conventionally has /objtype directories,
which contain among other things: include, for machine-
dependent include files; lib, for public object code
libraries; bin, for public programs; and mkfile, for precon-
ditioning mk(10.1).
For Inferno cross-compilation on all platforms, not just
Plan 9, both $objtype and $OBJTYPE are set by every native
kernel mkfile to correspond to the target processor type.
The Inferno mkfiles also set the -I option appropriately to
search the Inferno include directories, since the Plan 9
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2C(10.1) 2C(10.1)
defaults are inappropriate.
The compiler options are:
-o obj Place output in file obj (allowed only if there is
just one input file). Default is to take the last
element of the input file name, strip any trailing
.c, and append .O.
-w Print warning messages about unused variables,
etc.
-B Accept functions without a new-style ANSI C func-
tion prototype. By default, the compilers reject
functions used without a defined prototype,
although ANSI C permits them.
-Dname=def
-Dname Define the name to the preprocessor, as if by
`#define'. If no definition is given, the name is
defined as `1'.
-F Warn when the elements of a format (eg, those used
by print) disagree with in type or size with the
corresponding parameter, or there is a mismatch in
number. See the discussion of extensions, below.
-Idir An `#include' file whose name does not begin with
slash or is enclosed in double quotes is always
sought first in the directory of the file argu-
ment. If this fails, the -. flag is given or the
name is enclosed in <>, it is then sought in
directories named in -I options, then in
/sys/include, and finally in /$objtype/include.
-. Suppress the automatic searching for include files
in the directory of the file argument.
-N Suppress automatic registerization and optimiza-
tion.
-S Print an assembly language version of the object
code on standard output as well as generating the
.O file.
-T Pass type signatures on all external and global
entities. The signature is based on the C signof
operator, an extension in this compiler. See
dynld(10.2).
-V By default, the compilers are non-standardly lax
about type equality between void* values and other
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2C(10.1) 2C(10.1)
pointers; this flag requires ANSI C conformance.
-a Instead of compiling, print on standard output
acid functions (see acid(10.1)) for examining
structures declared in the source files.
-aa Like -a except suppress information about struc-
tures declared in included header files.
The compilers handle most preprocessing directives them-
selves, but support excludes the #if and #elif directives,
and the ## preprocessor operation.
The compilers support several extensions to ANSI C:
- A structure or union may contain unnamed substructures
and subunions. The fields of the substructures or sub-
unions can then be used as if they were members of the
parent structure or union (the resolution of a name
conflict is unspecified). When a pointer to the outer
structure or union is used in a context that is only
legal for the unnamed substructure, the compiler pro-
motes the type and adjusts the pointer value to point
at the substructure. If the unnamed structure or union
is of a type with a tag name specified by a typedef
statement, the unnamed structure or union can be
explicitly referenced by <struct variable>.<tagname>.
- A structure value can be formed with an expression such
as
(struct S){v1, v2, v3}
where the list elements are values for the fields of
struct S.
- Array initializers can specify the indices of the array
in square brackets, as
int a[] = { [3] 1, [10] 5 };
which initializes the third and tenth elements of the
eleven-element array a.
- Structure initializers can specify the structure ele-
ment by using the name following a period, as
struct { int x; int y; } s = { .y 1, .x 5 };
which initializes elements y and then x of the struc-
ture s. These forms also accept the new ANSI C nota-
tion, which includes an equal sign:
int a[] = { [3] = 1, [10] = 5 };
struct { int x; int y; } s = { .y = 1, .x = 5 };
- A global variable can be dedicated to a register by
declaring it extern register in all modules and
libraries.
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2C(10.1) 2C(10.1)
- A #pragma of the form
#pragma lib "libbio.a"
records that the program needs to be loaded with file
/$objtype/lib/libbio.a; such lines, typically placed in
library header files, obviate the -l option of the
loaders. To help identify files in non-standard direc-
tories, within the file names in the #pragmas the
string $M represents the name of the architecture
(e.g., mips) and $O represents its identifying charac-
ter (e.g., v).
- Two #pragma requests to define rules for checking
print-like formats (see the -F option above). One
#pragma tells for a given routine which argument is the
format. For example:
#pragma varargck argpos print 1
#pragma varargck argpos sprint 2
say that print has a format as its first argument, and
sprint has one as its second. Another #pragma associ-
ates format character sequences and types:
#pragma varargck type "lld" vlong
#pragma varargck type "lx" void*
#pragma varargck type "S" Rune*
where the format characters are those following the %
in the format (ignoring any preceding formatting
flags). Note the assumption that all formats arguments
are compatible. The system include files have appro-
priate #pragma lines for the standard format elements
and formatting functions.
- A #pragma of the form
#pragma incomplete type
tells the compiler that type should have its signature
calculated as an incomplete type even when it is fully
defined. This allows the type signature mechanism to
work in the presence of opaque types declared in header
files, with their full definitions visible only to the
code which manipulates them. With some imported soft-
ware it might be necessary to turn off the signature
generation completely for a large body of code (typi-
cally at the start and end of a particular include
file). If type is the word _off_, signature generation
is turned off; if type is the word _on_, the compiler
will generate signatures.
- The C++ comment (// to end of line) is accepted as well
as the normal convention of /* */.
- The compilers accept long long variables as a 64-bit
type. The standard header typedefs this to vlong.
Arithmetic on vlong values is usually emulated by a
run-time library.
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2C(10.1) 2C(10.1)
EXAMPLE
For the 68020, produce a program prog from C files main.c
and sub.c:
2c -FVw main.c sub.c
2l -o prog main.2 sub.2
FILES
/sys/include host system area for machine-independent
#include directives.
/$objtype/include host system area for machine-dependent
#include directives.
SOURCE
/utils/cc machine-independent part
/utils/2c, etc. machine-dependent part
SEE ALSO
2a(10.1), 2l(10.1), mk(10.1), inm(10.1), acid(10.1),
Rob Pike, ``How to Use the Plan 9 C Compiler''
BUGS
The preprocessor only handles `#define', `#include',
`#undef', `#ifdef', `#line', and `#ifndef'.
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