term% cat index.txt 2C(1) General Commands Manual 2C(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 cor‐
responding architecture. If there are multiple C files, the compilers
will attempt to keep $NPROC compilations running concurrently. Associ‐
ated with each compiler is a string objtype, for example
0c spim
little-endian MIPS 3000 family
1c 68000
Motorola MC68000
2c 68020
Motorola MC68020
5c arm little-endian ARM
6c amd64
AMD64 and compatibles (e.g., Intel EM64T)
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
The compilers handle most preprocessing directives themselves; a com‐
plete preprocessor is available in cpp(1), which must be run sepa‐
rately.
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 $objtype environment variable to the ob‐
jtype string appropriate to the current machine's type. Plan 9 also
conventionally has /objtype directories, which contain among other
things: include, for machine-dependent include files; lib, for public
object code libraries; bin, for public programs; and mkfile, for pre‐
conditioning mk(1).
The compiler options are:
-o obj Place output in file obj (allowed only if there is just one in‐
put file). Default is to take the last element of the input
file name, strip any trailing .c, and append .O.
-w Print warning messages about unused variables, etc.
-B Accept functions without a new-style ANSI C function prototype.
By default, the compilers reject functions used without a de‐
fined prototype, although ANSI C permits them.
-Dname=def
-Dname Define the name to the preprocessor, as if by If no definition
is given, the name is defined as
-F Enable type-checking of calls to print(2) and other formatted
print routines. See the discussion of extensions, below.
-Idir An file whose name does not begin with slash or is enclosed in
double quotes is always sought first in the directory of the
file argument. If this fails, the -. flag is given or the name
is enclosed in <>, it is then sought in directories named in -I
options, then in /sys/include, and finally in /$objtype/include.
-. Suppress the automatic searching for include files in the direc‐
tory of the file argument.
-N Suppress automatic registerization and optimization.
-S Print an assembly language version of the object code on stan‐
dard 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. See dynld(2).
-V By default, the compilers are non-standardly lax about type
equality between void* values and other pointers; this flag re‐
quires ANSI C conformance.
-p Invoke a standard ANSI C preprocessor before compiling.
-a Instead of compiling, print on standard output acid functions
(see acid(1)) for examining structures declared in the source
files.
-aa Like -a except suppress information about structures declared in
included header files.
-n When used with -a or -aa, places acid functions in file.acid for
input file.c, and not on standard output.
The compilers support several extensions to ANSI C:
- A structure or union may contain unnamed substructures and sub‐
unions. The fields of the substructures or subunions 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
promotes 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 vari‐
able>.<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-el‐
ement array a.
- Structure initializers can specify the structure element by us‐
ing 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 structure s.
These forms also accept the new ANSI C notation, 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.
- A #pragma of the form
#pragma lib "libbio.a"
records that the program needs to be loaded with file /$obj‐
type/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 directories, within the file
names in the #pragmas the string $M represents the name of the
architecture (e.g., mips) and $O represents its identifying
character (e.g., v).
- A #pragma of the form
#pragma varargck argpos error 2
tells the compiler that the second argument to error is a print-
like format string (see print(2)) that identifies the handling
of subsequent arguments. The #pragma
#pragma varargck type "s" char*
says that the format verb s processes an argument of type char*.
The #pragma
#pragma varargck flag 'c'
says that c is a flag character. These #pragmas are used, if
the -F option is enabled, to type-check calls to print and other
such routines.
- A #pragma with any of the following forms:
#pragma incomplete type
#pragma incomplete struct tag
#pragma incomplete union tag
where type is a typedef'd name for a structure or union type,
and tag is a structure or union tag, tells the compiler that the
corresponding type should have its signature calculated as an
incomplete type even if it is subsequently fully defined. This
allows the type signature mechanism to work in the presence of
opaque types declared in header files, with their full defini‐
tions visible only to the code which manipulates them. With
some imported software 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, though in at
least 8c, only division and modulus use the run-time library and
the other operators generate in-line code (and uvlong-expression
division-or-modulus (1<<constant) will turn into in-line bit op‐
erations, as is done for shorter unsigned expressions).
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
system area for machine-independent #include directives.
/$objtype/include
system area for machine-dependent #include directives.
SOURCE
/sys/src/cmd/cc
machine-independent part
/sys/src/cmd/2c, etc.
machine-dependent part
SEE ALSO
2a(1), 2l(1), cpp(1), mk(1), nm(1), pcc(1), db(1), acid(1)
Rob Pike, ``How to Use the Plan 9 C Compiler''
BUGS
The list of compilers given above is only partial, not all architec‐
tures are supported on all systems, some have been retired and some are
provided by third parties.
The default preprocessor only handles and For a full ANSI preprocessor,
use the p option.
The default search order for include files differs to that of cpp(1).
Some features of C99, the 1999 ANSI C standard, are implemented.
switch expressions may not be either signedness of vlong on 32-bit ar‐
chitectures (8c at least).
The implementation of vlong assignment can use a static location and
this can be disturbed by interrupts (e.g., notes) (8c at least).
2C(1)