2C(10.1) 2C(10.1)

0c, 1c, 2c, 5c, 6c, 7c, 8c, kc, qc, vc - C compilers

2c [ option ... ] [ file ... ]
etc.

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.
Sun SPARC
Power PC,
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:

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.
Print warning messages about unused variables, etc.
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.

Define the name to the preprocessor, as if by If no definition is given, the name is defined as
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.
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 directory of the file argument.
Suppress automatic registerization and optimization.
Print an assembly language version of the object code on standard output as well as generating the .O file.
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).
By default, the compilers are non-standardly lax about type equality between void* values and other pointers; this flag requires ANSI C conformance.
Instead of compiling, print on standard output acid functions (see acid(10.1)) for examining structures declared in the source files.
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.

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

/sys/include
host system area for machine-independent #include directives.
/$objtype/include
host system area for machine-dependent #include directives.

/utils/cc
machine-independent part
/utils/2c, etc.
machine-dependent part

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''

The preprocessor only handles and