tcc-doc.texi

tcc

\input texinfo @c -*- texinfo -*-
@c %**start of header
@setfilename tcc-doc.info
@settitle Tiny C Compiler Reference Documentation
@c %**end of header

@include config.texi

@iftex
@titlepage
@afourpaper
@sp 7
@center @titlefont{Tiny C Compiler Reference Documentation}
@sp 3
@end titlepage
@headings double
@end iftex

@c @ifhtml
@contents
@c @end ifhtml

@ifnothtml
@node Top, Introduction, (dir), (dir)
@top Tiny C Compiler Reference Documentation

This manual documents version @value{VERSION} of the Tiny C Compiler.

@menu
* Introduction::                Introduction to tcc.
* Invoke::                      Invocation of tcc (command line, options).
* Bounds::                      Automatic bounds-checking of C code.
* Libtcc::                      The libtcc library.
@end menu
@end ifnothtml

@node Introduction
@chapter Introduction

TinyCC (aka TCC) is a small but hyper fast C compiler. Unlike other C
compilers, it is meant to be self-relying: you do not need an
external assembler or linker because TCC does that for you.

TCC compiles so @emph{fast} that even for big projects @code{Makefile}s may
not be necessary. 

TCC not only supports ANSI C, but also most of the new ISO C99
standard and many GNUC extensions including inline assembly.

TCC can also be used to make @emph{C scripts}, i.e. pieces of C source
that you run as a Perl or Python script. Compilation is so fast that
your script will be as fast as if it was an executable.

TCC can also automatically generate memory and bound checks
(@pxref{Bounds}) while allowing all C pointers operations. TCC can do
these checks even if non patched libraries are used.

With @code{libtcc}, you can use TCC as a backend for dynamic code
generation (@pxref{Libtcc}).

@node Invoke
@chapter Command line invocation

[This manual documents version @value{VERSION} of the Tiny C Compiler]

@section Quick start

@example
@c man begin SYNOPSIS
usage: tcc [options] [@var{infile1} @var{infile2}@dots{}] [@option{-run} @var{infile} @var{args}@dots{}]
@c man end
@end example

@noindent
@c man begin DESCRIPTION
TCC options are a very much like gcc options. The main difference is that TCC
can also execute directly the resulting program and give it runtime
arguments.

Here are some examples to understand the logic:

@table @code
@item @samp{tcc -run a.c}
Compile @file{a.c} and execute it directly

@item @samp{tcc -run a.c arg1}
Compile a.c and execute it directly. arg1 is given as first argument to
the @code{main()} of a.c.

@item @samp{tcc a.c -run b.c arg1}
Compile @file{a.c} and @file{b.c}, link them together and execute them. arg1 is given
as first argument to the @code{main()} of the resulting program. Because
multiple C files are specified, @option{--} are necessary to clearly separate the
program arguments from the TCC options.

@item @samp{tcc -o myprog a.c b.c}
Compile @file{a.c} and @file{b.c}, link them and generate the executable @file{myprog}.

@item @samp{tcc -o myprog a.o b.o}
link @file{a.o} and @file{b.o} together and generate the executable @file{myprog}.

@item @samp{tcc -c a.c}
Compile @file{a.c} and generate object file @file{a.o}.

@item @samp{tcc -c asmfile.S}
Preprocess with C preprocess and assemble @file{asmfile.S} and generate
object file @file{asmfile.o}.

@item @samp{tcc -c asmfile.s}
Assemble (but not preprocess) @file{asmfile.s} and generate object file
@file{asmfile.o}.

@item @samp{tcc -r -o ab.o a.c b.c}
Compile @file{a.c} and @file{b.c}, link them together and generate the object file @file{ab.o}.

@end table

Scripting:

TCC can be invoked from @emph{scripts}, just as shell scripts. You just
need to add @code{#!/usr/local/bin/tcc -run} at the start of your C source:

@example
#!/usr/local/bin/tcc -run
#include <stdio.h>

int main() 
@{
    printf("Hello World\n");
    return 0;
@}
@end example
@c man end

@section Option summary

General Options:

@c man begin OPTIONS
@table @option
@item -v
Display current TCC version.

@item -c
Generate an object file (@option{-o} option must also be given).

@item -o outfile
Put object file, executable, or dll into output file @file{outfile}.

@item -Bdir
Set the path where the tcc internal libraries can be found (default is
@file{PREFIX/lib/tcc}).

@item -bench
Output compilation statistics.

@item -run source [args...]

Compile file @var{source} and run it with the command line arguments
@var{args}. In order to be able to give more than one argument to a
script, several TCC options can be given @emph{after} the
@option{-run} option, separated by spaces. Example:

@example
tcc "-run -L/usr/X11R6/lib -lX11" ex4.c
@end example

In a script, it gives the following header:

@example
#!/usr/local/bin/tcc -run -L/usr/X11R6/lib -lX11
#include <stdlib.h>
int main(int argc, char **argv)
@{
    ...
@}
@end example

@end table

Preprocessor options:

@table @option
@item -Idir
Specify an additional include path. Include paths are searched in the
order they are specified.

System include paths are always searched after. The default system
include paths are: @file{/usr/local/include}, @file{/usr/include}
and @file{PREFIX/lib/tcc/include}. (@file{PREFIX} is usually
@file{/usr} or @file{/usr/local}).

@item -Dsym[=val]
Define preprocessor symbol @samp{sym} to
val. If val is not present, its value is @samp{1}. Function-like macros can
also be defined: @option{-DF(a)=a+1}

@item -Usym
Undefine preprocessor symbol @samp{sym}.
@end table

Warning options:

@table @option
@item -w
Disable all warnings.

@end table

Note: each of the following warning options has a negative form beginning with
@option{-Wno-}.

@table @option
@item -Wunsupported
Warn about unsupported GCC features that are ignored by TCC.

@item -Wwrite-strings
Make string constants being of type @code{const char *} intead of @code{char
*}.

@item -Werror
Abort compilation if warnings are issued.

@item -Wall 
Activate all warnings, except @option{-Werror}, @option{-Wunusupported} and
@option{-Wwrite-strings} (currently not useful).

@end table

Linker options:

@table @option
@item -Ldir
Specify an additional static library path for the @option{-l} option. The
default library paths are @file{/usr/local/lib}, @file{/usr/lib} and @file{/lib}.

@item -lxxx
Link your program with dynamic library libxxx.so or static library
libxxx.a. The library is searched in the paths specified by the
@option{-L} option.

@item -shared
Generate a shared library instead of an executable (@option{-o} option
must also be given).

@item -static
Generate a statically linked executable (default is a shared linked
executable) (@option{-o} option must also be given).

@item -rdynamic
Export global symbols to the dynamic linker. It is useful when a library
opened with @code{dlopen()} needs to access executable symbols.

@item -r
Generate an object file combining all input files (@option{-o} option must
also be given).

@end table

Debugger options:

@table @option
@item -g
Generate run time debug information so that you get clear run time
error messages: @code{ test.c:68: in function 'test5()': dereferencing
invalid pointer} instead of the laconic @code{Segmentation
fault}.

@item -b
Generate additional support code to check
memory allocations and array/pointer bounds. @option{-g} is implied. Note
that the generated code is slower and bigger in this case.

@item -bt N
Display N callers in stack traces. This is useful with @option{-g} or
@option{-b}.

@end table

Note: GCC options @option{-Ox}, @option{-fx} and @option{-mx} are
ignored.
@c man end

@ignore

@setfilename tcc
@settitle Tiny C Compiler

@c man begin SEEALSO
gcc(1)
@c man end

@c man begin AUTHOR
Fabrice Bellard
@c man end

@end ignore

@chapter C language support

@section ANSI C

TCC implements all the ANSI C standard, including structure bit fields
and floating point numbers (@code{long double}, @code{double}, and
@code{float} fully supported).

@section ISOC99 extensions

TCC implements many features of the new C standard: ISO C99. Currently
missing items are: complex and imaginary numbers and variable length
arrays.

Currently implemented ISOC99 features:

@itemize

@item 64 bit @code{long long} types are fully supported.

@item The boolean type @code{_Bool} is supported.

@item @code{__func__} is a string variable containing the current
function name.

@item Variadic macros: @code{__VA_ARGS__} can be used for
   function-like macros:
@example
    #define dprintf(level, __VA_ARGS__) printf(__VA_ARGS__)
@end example

@noindent
@code{dprintf} can then be used with a variable number of parameters.

@item Declarations can appear anywhere in a block (as in C++).

@item Array and struct/union elements can be initialized in any order by
  using designators:
@example
    struct @{ int x, y; @} st[10] = @{ [0].x = 1, [0].y = 2 @};

    int tab[10] = @{ 1, 2, [5] = 5, [9] = 9@};
@end example
    
@item Compound initializers are supported:
@example
    int *p = (int [])@{ 1, 2, 3 @};
@end example
to initialize a pointer pointing to an initialized array. The same
works for structures and strings.

@item Hexadecimal floating point constants are supported:
@example
          double d = 0x1234p10;
@end example

@noindent
is the same as writing 
@example
          double d = 4771840.0;
@end example

@item @code{inline} keyword is ignored.

@item @code{restrict} keyword is ignored.
@end itemize

@section GNU C extensions

TCC implements some GNU C extensions:

@itemize

@item array designators can be used without '=': 
@example
    int a[10] = @{ [0] 1, [5] 2, 3, 4 @};
@end example

@item Structure field designators can be a label: 
@example
    struct @{ int x, y; @} st = @{ x: 1, y: 1@};
@end example
instead of
@example
    struct @{ int x, y; @} st = @{ .x = 1, .y = 1@};
@end example

@item @code{\e} is ASCII character 27.

@item case ranges : ranges can be used in @code{case}s:
@example
    switch(a) @{
    case 1 @dots{} 9:
          printf("range 1 to 9\n");
          break;
    default:
          printf("unexpected\n");
          break;
    @}
@end example

@item The keyword @code{__attribute__} is handled to specify variable or
function attributes. The following attributes are supported:
  @itemize
  @item @code{aligned(n)}: align data to n bytes (must be a power of two).

  @item @code{section(name)}: generate function or data in assembly
  section name (name is a string containing the section name) instead
  of the default section.

  @item @code{unused}: specify that the variable or the function is unused.

  @item @code{cdecl}: use standard C calling convention.

  @item @code{stdcall}: use Pascal-like calling convention.

  @end itemize

Here are some examples:
@example
    int a __attribute__ ((aligned(8), section(".mysection")));
@end example

@noindent
align variable @code{a} to 8 bytes and put it in section @code{.mysection}.

@example
    int my_add(int a, int b) __attribute__ ((section(".mycodesection"))) 
    @{
        return a + b;
    @}
@end example

@noindent
generate function @code{my_add} in section @code{.mycodesection}.

@item GNU style variadic macros:
@example
    #define dprintf(fmt, args@dots{}) printf(fmt, ## args)

    dprintf("no arg\n");
    dprintf("one arg %d\n", 1);
@end example

@item @code{__FUNCTION__} is interpreted as C99 @code{__func__} 
(so it has not exactly the same semantics as string literal GNUC
where it is a string literal).

@item The @code{__alignof__} keyword can be used as @code{sizeof} 
to get the alignment of a type or an expression.

@item The @code{typeof(x)} returns the type of @code{x}. 
@code{x} is an expression or a type.

@item Computed gotos: @code{&&label} returns a pointer of type 
@code{void *} on the goto label @code{label}. @code{goto *expr} can be
used to jump on the pointer resulting from @code{expr}.

@item Inline assembly with asm instruction:
@cindex inline assembly
@cindex assembly, inline
@cindex __asm__
@example
static inline void * my_memcpy(void * to, const void * from, size_t n)
@{
int d0, d1, d2;
__asm__ __volatile__(
        "rep ; movsl\n\t"
        "testb $2,%b4\n\t"
        "je 1f\n\t"
        "movsw\n"
        "1:\ttestb $1,%b4\n\t"
        "je 2f\n\t"
        "movsb\n"
        "2:"
        : "=&c" (d0), "=&D" (d1), "=&S" (d2)
        :"0" (n/4), "q" (n),"1" ((long) to),"2" ((long) from)
        : "memory");
return (to);
@}
@end example

@noindent
@cindex gas
TCC includes its own x86 inline assembler with a @code{gas}-like (GNU
assembler) syntax. No intermediate files are generated. GCC 3.x named
operands are supported.

@item @code{__builtin_types_compatible_p()} and @code{__builtin_constant_p()} 
are supported.

@end itemize

@section TinyCC extensions

@itemize

@item @code{__TINYC__} is a predefined macro to @code{1} to
indicate that you use TCC.

@item @code{#!} at the start of a line is ignored to allow scripting.

@item Binary digits can be entered (@code{0b101} instead of
@code{5}).

@item @code{__BOUNDS_CHECKING_ON} is defined if bound checking is activated.

@end itemize

@chapter TinyCC Assembler

Since version 0.9.16, TinyCC integrates its own assembler. TinyCC
assembler supports a gas-like syntax (GNU assembler). You can
desactivate assembler support if you want a smaller TinyCC executable
(the C compiler does not rely on the assembler).

TinyCC Assembler is used to handle files with @file{.S} (C
preprocessed assembler) and @file{.s} extensions. It is also used to
handle the GNU inline assembler with the @code{asm} keyword.

@section Syntax

TinyCC Assembler supports most of the gas syntax. The tokens are the
same as C.

@itemize

@item C and C++ comments are supported.

@item Identifiers are the same as C, so you cannot use '.' or '$'.

@item Only 32 bit integer numbers are supported.

@end itemize

@section Expressions

@itemize

@item Integers in decimal, octal and hexa are supported.

@item Unary operators: +, -, ~.

@item Binary operators in decreasing priority order:

@enumerate
@item *, /, %
@item &, |, ^
@item +, -
@end enumerate

@item A value is either an absolute number or a label plus an offset. 
All operators accept absolute values except '+' and '-'. '+' or '-' can be
used to add an offset to a label. '-' supports two labels only if they
are the same or if they are both defined and in the same section.

@end itemize

@section Labels

@itemize

@item All labels are considered as local, except undefined ones.

@item Numeric labels can be used as local @code{gas}-like labels. 
They can be defined several times in the same source. Use 'b'
(backward) or 'f' (forward) as suffix to reference them: