511 lines
9.6 KiB
Plaintext
511 lines
9.6 KiB
Plaintext
.TH 2C 1
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.SH NAME
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0c, 1c, 2c, 5c, 6c, 7c, 8c, kc, qc, vc \- C compilers
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.SH SYNOPSIS
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.B 2c
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[
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.I option ...
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]
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[
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.I file ...
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]
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.br
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etc.
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.SH DESCRIPTION
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These commands compile the named C
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.I files
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into object files for the corresponding architecture.
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If there are multiple C
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.IR files ,
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the compilers will attempt to keep
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.B $NPROC
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compilations running concurrently.
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Associated with each compiler is a string
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.IR objtype ,
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for example
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.TF "6c amd64 "
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.PD
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.TP
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.B "0c spim
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little-endian MIPS 3000 family
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.TP
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.B "1c 68000
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Motorola MC68000
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.TP
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.B "2c 68020
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Motorola MC68020
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.TP
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.B "5c arm
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little-endian ARM
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.TP
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.B "6c amd64
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AMD64 and compatibles (e.g., Intel EM64T)
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.TP
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.B "7c arm64
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ARM64 (ARMv8)
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.TP
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.B "8c 386
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Intel i386, i486, Pentium, etc.
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.TP
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.B "kc sparc
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Sun SPARC
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.TP
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.B "qc power
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Power PC
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.TP
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.B "vc mips
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big-endian MIPS 3000 family
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.PP
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The compilers handle most preprocessing directives themselves; a complete
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preprocessor is available in
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.IR cpp (1),
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which must be run separately.
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.PP
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Let the first letter of the compiler name be
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.IR O =
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.BR 0 ,
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.BR 1 ,
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.BR 2 ,
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.BR 5 ,
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.BR 6 ,
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.BR 7 ,
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.BR 8 ,
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.BR k ,
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.BR q ,
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or
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.BR v .
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The output object files end in
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.RI . O .
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The letter is also the prefix of related programs:
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.IB O a
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is the assembler,
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.IB O l
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is the loader.
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Plan 9 conventionally sets the
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.B $objtype
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environment variable to the
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.I objtype
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string appropriate to the current machine's type.
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Plan 9 also conventionally has
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.RI / objtype
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directories, which contain among other things:
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.BR include ,
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for machine-dependent include files;
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.BR lib ,
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for public object code libraries;
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.BR bin ,
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for public programs;
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and
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.BR mkfile ,
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for preconditioning
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.IR mk (1).
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.PP
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The compiler options are:
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.TF Dname
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.PD
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.TP
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.BI -o " obj"
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Place output in file
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.I obj
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(allowed only if there is just one input file).
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Default is to take the last element of the input file name,
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strip any trailing
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.BR .c ,
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and append
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.RI . O .
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.TP
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.B -w
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Print warning messages about unused variables, etc.
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.TP
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.B -B
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Accept functions without a new-style
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ANSI C function prototype.
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By default, the compilers reject functions
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used without a defined prototype,
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although ANSI C permits them.
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.TP
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.BI -D\*S name=def
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.br
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.ns
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.TP
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.BI -D \*Sname
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Define the
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.I name
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to the preprocessor,
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as if by
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.LR #define .
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If no definition is given, the name is defined as
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.LR 1 .
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.TP
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.BI -F
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Enable type-checking of calls to
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.IR print (2)
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and other formatted print routines. See the discussion
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of extensions, below.
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.TP
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.BI -I \*Sdir
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An
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.L #include
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file whose name does not begin with
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slash
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or is enclosed in double quotes
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is always
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sought first in the directory
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of the
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.I file
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argument. If this fails,
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the
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.I -.
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flag is given or the name is enclosed in
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.BR <> ,
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it is then sought
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in directories named in
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.B -I
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options,
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then in
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.BR /sys/include ,
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and finally in
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.BR /$objtype/include .
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.TP
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.B -.
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Suppress the automatic searching for include files in
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the directory of the file argument.
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.TP
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.B -N
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Suppress automatic registerization and optimization.
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.TP
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.B -S
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Print an assembly language version of the object code
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on standard output as well as generating the
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.RI . O
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file.
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.TP
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.B -T
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Pass type signatures on all external and global entities.
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The signature is based on the C
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.B signof
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operator.
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.TP
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.B -V
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By default, the compilers are non-standardly lax about type equality between
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.B void*
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values and other pointers; this flag requires ANSI C conformance.
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.TP
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.B -p
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Invoke a standard ANSI C preprocessor before compiling.
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.TP
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.B -a
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Instead of compiling, print on standard output acid functions (see
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.IR acid (1))
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for examining structures declared in the source files.
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.TP
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.B -aa
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Like
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.B -a
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except suppress information about structures
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declared in included header files.
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.TP
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.B -n
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When used with
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.B -a
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or
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.BR -aa ,
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places acid functions in
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.IB file .acid
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for input
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.IB file .c ,
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and not on standard output.
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.PP
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The compilers support several extensions to ANSI C:
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.TF \|
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.PD
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.TP
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\-
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A structure or union may contain unnamed substructures and subunions.
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The fields of the substructures or
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subunions can then be used as if they were members of the parent
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structure or union (the resolution of a name conflict is unspecified).
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When a pointer to the outer structure or union is used in a context
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that is only legal for the unnamed substructure, the compiler promotes
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the type and adjusts the pointer value to point at the substructure.
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If the unnamed structure or union is of a type with a tag name specified by a
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.B typedef
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statement,
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the unnamed structure or union can be explicitly referenced
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by <struct variable>.<tagname>.
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.TP
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\-
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A structure value can be formed with an expression such as
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.EX
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(struct S){v1, v2, v3}
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.EE
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where the list elements are values for the fields of struct
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.BR S .
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.TP
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\-
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Array initializers can specify the indices of the array in square
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brackets, as
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.EX
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int a[] = { [3] 1, [10] 5 };
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.EE
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which initializes the third and tenth elements of the eleven-element array
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.BR a .
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.TP
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\-
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Structure initializers can specify the structure element by using the name
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following a period, as
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.EX
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struct { int x; int y; } s = { .y 1, .x 5 };
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.EE
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which initializes elements
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.B y
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and then
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.B x
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of the structure
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.BR s .
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These forms also accept the new ANSI C notation, which includes an equal sign:
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.EX
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int a[] = { [3] = 1, [10] = 5 };
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struct { int x; int y; } s = { .y = 1, .x = 5 };
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.EE
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.TP
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\-
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A global variable can be dedicated to a register
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by declaring it
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.B "extern register"
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in
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.I all
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modules and libraries.
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.TP
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\-
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A
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.B #pragma
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of the form
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.EX
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#pragma lib "libbio.a"
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.EE
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records that the program needs to be loaded with file
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.BR /$objtype/lib/libbio.a ;
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such lines, typically placed in library header files, obviate the
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.B -l
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option of the loaders. To help identify files in non-standard directories,
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within the file names in the
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.B #pragmas
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the string
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.B $M
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represents the name of the architecture
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(e.g.,
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.BR mips )
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and
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.B $O
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represents its identifying character
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(e.g.,
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.BR v ).
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.TP
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\-
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A
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.B #pragma
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of the form
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.EX
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#pragma varargck argpos error 2
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.EE
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tells the compiler that the second argument to
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.B error
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is a
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.BR print -like
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format string (see
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.IR print (2))
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that identifies the handling of subsequent arguments.
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The
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.B #pragma
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.EX
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#pragma varargck type "s" char*
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.EE
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says that the format verb
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.B s
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processes an argument of type
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.BR char *.
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The
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.B #pragma
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.EX
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#pragma varargck flag 'c'
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.EE
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says that
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.B c
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is a flag character.
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These
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.B #pragmas
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are used, if the
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.B -F
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option is enabled, to type-check calls to
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.B print
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and other such routines.
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.TP
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\-
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A
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.B #pragma
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with any of the following forms:
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.EX
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#pragma incomplete \fItype\fP
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#pragma incomplete struct \fItag\fP
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#pragma incomplete union \fItag\fP
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.EE
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where
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.I type
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is a
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.BR typedef 'd
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name for a structure or union type, and
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.I tag
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is a structure or union tag,
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tells the compiler that
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the corresponding type
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should have its signature calculated as an incomplete type
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even if it is subsequently fully defined.
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This allows the type signature mechanism to work in the presence
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of opaque types declared in header files, with their full definitions
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visible only to the code which manipulates them.
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With some imported software it might be necessary to turn off the
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signature generation completely for a large body of code (typically
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at the start and end of a particular include file).
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If
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.I type
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is the word
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.BR _off_ ,
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signature generation is turned off; if
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.I type
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is the word
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.BR _on_ ,
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the compiler will generate signatures.
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.TP
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\-
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The C++ comment
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.RB ( //
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to end of line)
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is accepted as well as the normal
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convention of
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.B /*
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.BR */ .
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.TP
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\-
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The compilers accept
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.B long
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.B long
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variables as a 64-bit type.
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The standard header typedefs this to
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.BR vlong .
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Arithmetic on
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.B vlong
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values is usually emulated by a run-time library,
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though in at least
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.IR 8c ,
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only division and modulus use the run-time library
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and the other operators generate in-line code
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(and
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.I uvlong-expression
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.I division-or-modulus
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.BI "(1<<" constant )
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will turn into in-line bit operations,
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as is done for shorter
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.I unsigned
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expressions).
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.PP
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Other differences with ANSI C include
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.TF \|
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.PD
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.TP
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\-
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The compilers use the original "unsigned preserving", rather than ANSI C "value preserving" rules, which means that, e.g.,
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.B "unsigned char"
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gets promoted to
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.B "unsigned int"
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rather than
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.BR "int" .
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.TP
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\-
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Parameters in macros are substituted inside of strings.
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.SH EXAMPLE
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For the 68020, produce a program
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.B prog
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from C files
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.BR main.c
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and
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.BR sub.c :
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.IP
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.EX
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2c -FVw main.c sub.c
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2l -o prog main.2 sub.2
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.EE
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.SH FILES
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.TF /$objtype/include
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.TP
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.B /sys/include
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system area for machine-independent
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.B #include
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directives.
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.TP
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.B /$objtype/include
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system area for machine-dependent
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.B #include
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directives.
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.SH SOURCE
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.TF /sys/src/cmd/2c,\ etc.
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.TP
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.B /sys/src/cmd/cc
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machine-independent part
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.TP
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.BR /sys/src/cmd/2c ,\ etc.
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machine-dependent part
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.SH "SEE ALSO"
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.IR 2a (1),
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.IR 2l (1),
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.IR cpp (1),
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.IR mk (1),
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.IR nm (1),
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.IR pcc (1),
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.IR db (1),
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.IR acid (1)
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.\" .IR ansitize (1)
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.PP
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Rob Pike,
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``How to Use the Plan 9 C Compiler''
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.SH BUGS
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The list of compilers given above is only partial,
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not all architectures are supported on all systems,
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some have been retired and some
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are provided by third parties.
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.PP
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The default preprocessor only handles
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.LR #define ,
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.LR #include ,
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.LR #undef ,
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.LR #ifdef ,
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.LR #line ,
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and
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.LR #ifndef .
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For a full ANSI preprocessor, use
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the
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.B p
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option.
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.PP
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The default search order for include files
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differs to that of
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.IR cpp (1).
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.PP
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Some features of C99, the 1999 ANSI C standard,
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are implemented.
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.PP
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.B switch
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expressions may not be either signedness of
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.B vlong
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on 32-bit architectures
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.RI ( 8c
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at least).
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.PP
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The implementation of
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.B vlong
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assignment can use a static location
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and this can be disturbed by interrupts
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(e.g., notes)
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.RI ( 8c
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at least).
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