Tiny C Compiler Reference Documentation

Table of Contents

1. Introduction

2. Command line invocation

2.1 Quick start

2.2 Option summary

3. C language support

3.1 ANSI C

3.2 ISOC99 extensions

3.3 GNU C extensions

3.4 TinyCC extensions

4. TinyCC Assembler

4.1 Syntax

4.2 Expressions

4.3 Labels

4.4 Directives

4.5 X86 Assembler

5. TinyCC Linker

5.1 ELF file generation

5.2 ELF file loader

5.3 PE-i386 file generation

5.4 GNU Linker Scripts

6. TinyCC Memory and Bound checks

7. The libtcc library

8. Developer's guide

8.1 File reading

8.2 Lexer

8.3 Parser

8.4 Types

8.5 Symbols

8.6 Sections

8.7 Code generation

8.7.1 Introduction

8.7.2 The value stack

8.7.3 Manipulating the value stack

8.7.4 CPU dependent code generation

8.8 Optimizations done

Concept Index

1. 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 fast that even for big projects Makefiles 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 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

(see section 6. TinyCC Memory and Bound checks) while allowing all C pointers operations. TCC can do

these checks even if non patched libraries are used.

With libtcc, you can use TCC as a backend for dynamic code

generation (see section 7. The libtcc library).

TCC mainly supports the i386 target on Linux and Windows. There are alpha

ports for the ARM (arm-tcc) and the TMS320C67xx targets

(c67-tcc). More information about the ARM port is available at

http://lists.gnu.org/archive/html/tinycc-devel/2003-10/msg00044.html.

2. Command line invocation

[This manual documents version 0.9.23 of the Tiny C Compiler]

2.1 Quick start

usage: tcc [options] [infile1 infile2...] [`-run' infile args...]

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:

`tcc -run a.c'

Compile `a.c' and execute it directly

`tcc -run a.c arg1'

Compile a.c and execute it directly. arg1 is given as first argument to

the main() of a.c.

`tcc a.c -run b.c arg1'

Compile `a.c' and `b.c', link them together and execute them. arg1 is given

as first argument to the main() of the resulting program. Because

multiple C files are specified, `--' are necessary to clearly separate the

program arguments from the TCC options.

`tcc -o myprog a.c b.c'

Compile `a.c' and `b.c', link them and generate the executable `myprog'.

`tcc -o myprog a.o b.o'

link `a.o' and `b.o' together and generate the executable `myprog'.

`tcc -c a.c'

Compile `a.c' and generate object file `a.o'.

`tcc -c asmfile.S'

Preprocess with C preprocess and assemble `asmfile.S' and generate

object file `asmfile.o'.

`tcc -c asmfile.s'

Assemble (but not preprocess) `asmfile.s' and generate object file

`asmfile.o'.

`tcc -r -o ab.o a.c b.c'

Compile `a.c' and `b.c', link them together and generate the object file `ab.o'.

Scripting:

TCC can be invoked from scripts, just as shell scripts. You just

need to add #!/usr/local/bin/tcc -run at the start of your C source:

#!/usr/local/bin/tcc -run

#include <stdio.h>

int main()

{

    printf("Hello World\n");

    return 0;

}

2.2 Option summary

General Options:

`-v'

Display current TCC version.

`-c'

Generate an object file (`-o' option must also be given).

`-o outfile'

Put object file, executable, or dll into output file `outfile'.

`-Bdir'

Set the path where the tcc internal libraries can be found (default is

`PREFIX/lib/tcc').

`-bench'

Output compilation statistics.

`-run source [args...]'

Compile file source and run it with the command line arguments

args. In order to be able to give more than one argument to a

script, several TCC options can be given after the

`-run' option, separated by spaces. Example:

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

In a script, it gives the following header:

#!/usr/local/bin/tcc -run -L/usr/X11R6/lib -lX11

#include <stdlib.h>

int main(int argc, char **argv)

{

    ...

}

Preprocessor options:

`-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: `/usr/local/include', `/usr/include'

and `PREFIX/lib/tcc/include'. (`PREFIX' is usually

`/usr' or `/usr/local').

`-Dsym[=val]'

Define preprocessor symbol `sym' to

val. If val is not present, its value is `1'. Function-like macros can

also be defined: `-DF(a)=a+1'

`-Usym'

Undefine preprocessor symbol `sym'.

Compilation flags:

Note: each of the following warning options has a negative form beginning with

`-fno-'.

`-funsigned-char'

Let the char type be unsigned.

`-fsigned-char'

Let the char type be signed.

`-fno-common'

Do not generate common symbols for uninitialized data.

`-fleading-underscore'

Add a leading underscore at the beginning of each C symbol.

Warning options:

`-w'

Disable all warnings.

Note: each of the following warning options has a negative form beginning with

`-Wno-'.

`-Wimplicit-function-declaration'

Warn about implicit function declaration.

`-Wunsupported'

Warn about unsupported GCC features that are ignored by TCC.

`-Wwrite-strings'

Make string constants be of type const char * instead of char

*.

`-Werror'

Abort compilation if warnings are issued.

`-Wall'

Activate all warnings, except `-Werror', `-Wunusupported' and

`-Wwrite-strings'.

Linker options:

`-Ldir'

Specify an additional static library path for the `-l' option. The

default library paths are `/usr/local/lib', `/usr/lib' and `/lib'.

`-lxxx'

Link your program with dynamic library libxxx.so or static library

libxxx.a. The library is searched in the paths specified by the

`-L' option.

`-shared'

Generate a shared library instead of an executable (`-o' option

must also be given).

`-static'

Generate a statically linked executable (default is a shared linked

executable) (`-o' option must also be given).

`-rdynamic'

Export global symbols to the dynamic linker. It is useful when a library

opened with dlopen() needs to access executable symbols.

`-r'

Generate an object file combining all input files (`-o' option must

also be given).

`-Wl,-Ttext,address'

Set the start of the .text section to address.

`-Wl,--oformat,fmt'

Use fmt as output format. The supported output formats are:

elf32-i386

ELF output format (default)

binary

Binary image (only for executable output)

coff

COFF output format (only for executable output for TMS320C67xx target)

Debugger options:

`-g'

Generate run time debug information so that you get clear run time

error messages:  test.c:68: in function 'test5()': dereferencing

invalid pointer instead of the laconic Segmentation

fault.

`-b'

Generate additional support code to check

memory allocations and array/pointer bounds. `-g' is implied. Note

that the generated code is slower and bigger in this case.

`-bt N'

Display N callers in stack traces. This is useful with `-g' or

`-b'.

Note: GCC options `-Ox', `-fx' and `-mx' are

ignored.

3. C language support

3.1 ANSI C

TCC implements all the ANSI C standard, including structure bit fields

and floating point numbers (long double, double, and

float fully supported).

3.2 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:

64 bit long long types are fully supported.

The boolean type _Bool is supported.

__func__ is a string variable containing the current

function name.

Variadic macros: __VA_ARGS__ can be used for

   function-like macros:

    #define dprintf(level, __VA_ARGS__) printf(__VA_ARGS__)

dprintf can then be used with a variable number of parameters.

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

Array and struct/union elements can be initialized in any order by

  using designators:

    struct { int x, y; } st[10] = { [0].x = 1, [0].y = 2 };

    int tab[10] = { 1, 2, [5] = 5, [9] = 9};

Compound initializers are supported:

    int *p = (int []){ 1, 2, 3 };

to initialize a pointer pointing to an initialized array. The same

works for structures and strings.

Hexadecimal floating point constants are supported:

          double d = 0x1234p10;

is the same as writing

          double d = 4771840.0;

inline keyword is ignored.

restrict keyword is ignored.

3.3 GNU C extensions

TCC implements some GNU C extensions:

array designators can be used without '=':

    int a[10] = { [0] 1, [5] 2, 3, 4 };

Structure field designators can be a label:

    struct { int x, y; } st = { x: 1, y: 1};

instead of

    struct { int x, y; } st = { .x = 1, .y = 1};

\e is ASCII character 27.

case ranges : ranges can be used in cases:

    switch(a) {

    case 1 ... 9:

          printf("range 1 to 9\n");

          break;

    default:

          printf("unexpected\n");

          break;

    }

The keyword __attribute__ is handled to specify variable or

function attributes. The following attributes are supported:

aligned(n): align a variable or a structure field to n bytes

(must be a power of two).

packed: force alignment of a variable or a structure field to

  1.

section(name): generate function or data in assembly section

name (name is a string containing the section name) instead of the default

section.

unused: specify that the variable or the function is unused.

cdecl: use standard C calling convention (default).

stdcall: use Pascal-like calling convention.

regparm(n): use fast i386 calling convention. n must be

between 1 and 3. The first n function parameters are respectively put in

registers %eax, %edx and %ecx.

Here are some examples:

    int a __attribute__ ((aligned(8), section(".mysection")));

align variable a to 8 bytes and put it in section .mysection.

    int my_add(int a, int b) __attribute__ ((section(".mycodesection")))

    {

        return a + b;

    }

generate function my_add in section .mycodesection.

GNU style variadic macros:

    #define dprintf(fmt, args...) printf(fmt, ## args)

    dprintf("no arg\n");

    dprintf("one arg %d\n", 1);

__FUNCTION__ is interpreted as C99 __func__

(so it has not exactly the same semantics as string literal GNUC

where it is a string literal).

The __alignof__ keyword can be used as sizeof

to get the alignment of a type or an expression.

The typeof(x) returns the type of x.

x is an expression or a type.

Computed gotos: &&label returns a pointer of type

void * on the goto label label. goto *expr can be

used to jump on the pointer resulting from expr.

Inline assembly with asm instruction:

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);

}

TCC includes its own x86 inline assembler with a gas-like (GNU

assembler) syntax. No intermediate files are generated. GCC 3.x named

operands are supported.

__builtin_types_compatible_p() and __builtin_constant_p()

are supported.

#pragma pack is supported for win32 compatibility.

3.4 TinyCC extensions

__TINYC__ is a predefined macro to 1 to

indicate that you use TCC.

#! at the start of a line is ignored to allow scripting.

Binary digits can be entered (0b101 instead of

5).

__BOUNDS_CHECKING_ON is defined if bound checking is activated.

4. 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 `.S' (C

preprocessed assembler) and `.s' extensions. It is also used to

handle the GNU inline assembler with the asm keyword.

4.1 Syntax

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

same as C.

C and C++ comments are supported.

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

Only 32 bit integer numbers are supported.

4.2 Expressions

Integers in decimal, octal and hexa are supported.

Unary operators: +, -, ~.

Binary operators in decreasing priority order:

*, /, %

&, |, ^

+, -

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.

4.3 Labels

All labels are considered as local, except undefined ones.

Numeric labels can be used as local gas-like labels.

They can be defined several times in the same source. Use 'b'

(backward) or 'f' (forward) as suffix to reference them:

 1:

      jmp 1b /* jump to '1' label before */

      jmp 1f /* jump to '1' label after */

 1:

4.4 Directives

All directives are preceeded by a '.'. The following directives are

supported:

.align n[,value]

.skip n[,value]

.space n[,value]

.byte value1[,...]

.word value1[,...]

.short value1[,...]

.int value1[,...]

.long value1[,...]

.quad immediate_value1[,...]

.globl symbol

.global symbol

.section section

.text

.data

.bss

.fill repeat[,size[,value]]

.org n

.previous

.string string[,...]

.asciz string[,...]

.ascii string[,...]

4.5 X86 Assembler

All X86 opcodes are supported. Only ATT syntax is supported (source

then destination operand order). If no size suffix is given, TinyCC

tries to guess it from the operand sizes.

Currently, MMX opcodes are supported but not SSE ones.

5. TinyCC Linker

5.1 ELF file generation

TCC can directly output relocatable ELF files (object files),

executable ELF files and dynamic ELF libraries without relying on an

external linker.

Dynamic ELF libraries can be output but the C compiler does not generate

position independent code (PIC). It means that the dynamic library

code generated by TCC cannot be factorized among processes yet.

TCC linker eliminates unreferenced object code in libraries. A single pass is

done on the object and library list, so the order in which object files and

libraries are specified is important (same constraint as GNU ld). No grouping

options (`--start-group' and `--end-group') are supported.

5.2 ELF file loader

TCC can load ELF object files, archives (.a files) and dynamic

libraries (.so).

5.3 PE-i386 file generation

TCC for Windows supports the native Win32 executable file format (PE-i386). It

generates both EXE and DLL files. DLL symbols can be imported thru DEF files

generated with the tiny_impdef tool.

Currently TCC for Windows cannot generate nor read PE object files, so ELF

object files are used for that purpose. It can be a problem if

interoperability with MSVC is needed. Moreover, no leading underscore is

currently generated in the ELF symbols.

5.4 GNU Linker Scripts

Because on many Linux systems some dynamic libraries (such as

`/usr/lib/libc.so') are in fact GNU ld link scripts (horrible!),

the TCC linker also supports a subset of GNU ld scripts.

The GROUP and FILE commands are supported. OUTPUT_FORMAT

and TARGET are ignored.

Example from `/usr/lib/libc.so':

/* GNU ld script

   Use the shared library, but some functions are only in

   the static library, so try that secondarily.  */

GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a )

6. TinyCC Memory and Bound checks

This feature is activated with the `-b' (see section 2. Command line invocation).

Note that pointer size is unchanged and that code generated

with bound checks is fully compatible with unchecked

code. When a pointer comes from unchecked code, it is assumed to be

valid. Even very obscure C code with casts should work correctly.

For more information about the ideas behind this method, see

http://www.doc.ic.ac.uk/~phjk/BoundsChecking.html.

Here are some examples of caught errors: