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 preconditioning
mk(10.1).
For Inferno cross-compilation on all platforms, not just Plan 9, both
$objtype
and
$OBJTYPE
are set by every native kernel
mkfile
to correspond to the target processor type.
The Inferno
mkfiles
also set the
-I
option appropriately to search the Inferno include directories,
since the Plan 9 defaults are inappropriate.
The compiler options are:
- -o obj
- Place output in file
obj
(allowed only if there is just one input file).
Default is to take the last element of the input file name,
strip any trailing
.c,
and append
.O.
- -w
- Print warning messages about unused variables, etc.
- -B
- Accept functions without a new-style
ANSI C function prototype.
By default, the compilers reject functions
used without a defined prototype,
although ANSI C permits them.
- -Dname=def
- -Dname
- Define the
name
to the preprocessor,
as if by
#define.
If no definition is given, the name is defined as
1.
- -F
- Warn when the elements of a format
(eg, those used by
print)
disagree with in type or size with the corresponding parameter,
or there is a mismatch in number.
See the discussion of extensions, below.
- -Idir
- An
#include
file whose name does not begin with
slash
or is enclosed in double quotes
is always
sought first in the directory
of the
file
argument. If this fails,
the
-.
flag is given or the name is enclosed in
<>,
it is then sought
in directories named in
-I
options,
then in
/sys/include,
and finally in
/$objtype/include.
- -.
- Suppress the automatic searching for include files in
the directory of the file argument.
- -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.
- -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 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 structures
declared in included header files.
The compilers handle most preprocessing directives themselves, 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
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 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 element 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 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
/$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 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).
- -
- 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
associates 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 appropriate
#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 software it might be necessary to turn off the
signature generation completely for a large body of code (typically
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.