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Plan 9 - man page for 2c (plan9 section 1)

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 handle 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 $objtype environment variable to the objtype string appropriate to the current machine's type. Plan 9 also convention- ally has /objtype directories, which contain among other things: include, for machine-dependent include files; lib, for public object code libraries; bin, for public programs; and mkfile, for preconditioning mk(1). The compiler options are: -o obj Place output in file obj (allowed only if there is just one input file). Default is to take the last element of the input file name, strip any trailing .c, and append .O. -w Print warning messages about unused variables, etc. -B Accept functions without a new-style ANSI C function prototype. By default, the compilers reject functions used without a defined prototype, although ANSI C permits them. -Dname=def -Dname Define the name to the preprocessor, as if by If no definition is given, the name is defined as -Idir An file whose name does not begin with slash or is enclosed in double quotes is always sought first in the directory of the file argument. If this fails, or the name is enclosed in <>, it is then sought in directories named in -I options, then in /sys/include, and finally in /$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 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 con- text 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 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 /$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 $O represents its identifying character (e.g., v). - The C++ comment (// to end of line) is accepted as well as the normal convention of /* */. - The compilers accept long long variables as a 64-bit type. The standard header typedefs this to vlong. The vlong runtime is slow.
EXAMPLE
For the 68020, produce a program prog from C files main.c and sub.c: 2c -w main.c sub.c 2l -o prog main.2 sub.2
FILES
/sys/include system area for machine-independent #include directives. /$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)


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