term% cat index.txt 2C(1) General Commands Manual 2C(1)
NAME
2c, 6c, 8c, kc, vc, xc - C compilers
SYNOPSIS
2c [ option ... ] [ file ... ]
6c [ option ... ] [ file ... ]
8c [ option ... ] [ file ... ]
kc [ option ... ] [ file ... ]
vc [ option ... ] [ file ... ]
xc [ option ... ] [ file ... ]
DESCRIPTION
2c, 6c, 8c, kc, vc, and xc compile the named C files into MC68020,
i960, i386, SPARC, MIPS, and ATT3210 object files. The compilers han‐
dle most preprocessing directives themselves; a complete preprocessor
is available in cpp(1), which must be run separately.
Let the first letter of the compiler name be O= 2, 6, 8, k, v, or x.
The output object files end in .O. The letter is also the prefix of
related programs: Oa is the assembler, Ol is the loader. Associated
with each compiler is a string objtype= 68020, 960, 386, sparc, mips,
or 3210. Plan 9 conventionally sets the $objtype environment variable
to the objtype string appropriate to the current machine's type. Plan
9 also conventionally has /objtype directories, which contain among
other things: include, for machine-dependent include files; lib, for
public object code libraries; bin, for public programs; and mkfile, for
preconditioning mk(1).
The compiler options are:
-o obj Place output in file obj (allowed only if there is just one
input file). Default is to take the last element of the in‐
put file name, strip any trailing .c, and append .O.
-w Print warning messages about unused variables, etc.
-B Accept functions without a new-style ANSI C function proto‐
type. By default, the compilers reject functions used with‐
out a defined prototype, although ANSI C permits them.
-Dname=def
-Dname Define the name to the preprocessor, as if by If no defini‐
tion is given, the name is defined as
-Idir An file whose name does not begin with slash or is enclosed
in double quotes is always sought first in the directory of
the file argument. If this fails, or the name is enclosed in
<>, it is then sought in directories named in -I options,
then in /sys/include, and finally in /$objtype/include.
-N Suppress automatic registerization and optimization.
-S Print an assembly language version of the object code on
standard output as well as generating the .O file.
-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.
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
int struct { int x; int y; } s = { .y 1, .x 5 };
which initializes elements y and then x of the structure s.
- 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 $O represents its identifying
character (e.g., v).
- The C++ comment (// to end of line) is accepted as well as the
normal convention of /* */.
- The compilers accept long long variables as a 64-bit type. The
standard header typedefs this to vlong. The vlong runtime is
slow.
EXAMPLE
For the 68020, produce a program prog from C files main.c and sub.c:
2c -w main.c sub.c
2l -o prog main.2 sub.2
FILES
/sys/include
system area for machine-independent #include directives.
/$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 i960 compiler has been used only to program one I/O controller and
is certainly buggy.
The preprocessor only handles and For a full ANSI preprocessor, use
cpp(1) on the files first.
2C(1)