libtcc library
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.
[This manual documents version 0.9.23 of the Tiny C Compiler]
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'
`tcc -run a.c arg1'
main() of a.c.
`tcc a.c -run b.c arg1'
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'
`tcc -o myprog a.o b.o'
`tcc -c a.c'
`tcc -c asmfile.S'
`tcc -c asmfile.s'
`tcc -r -o ab.o a.c b.c'
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;
}
General Options:
tcc "-run -L/usr/X11R6/lib -lX11" ex4.cIn 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:
Compilation flags:
Note: each of the following warning options has a negative form beginning with `-fno-'.
char type be unsigned.
char type be signed.
Warning options:
Note: each of the following warning options has a negative form beginning with `-Wno-'.
const char * instead of char
*.
Linker options:
dlopen() needs to access executable symbols.
elf32-i386
binary
coff
Debugger options:
test.c:68: in function 'test5()': dereferencing
invalid pointer instead of the laconic Segmentation
fault.
Note: GCC options `-Ox', `-fx' and `-mx' are ignored.
TCC implements all the ANSI C standard, including structure bit fields
and floating point numbers (long double, double, and
float fully supported).
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:
long long types are fully supported.
_Bool is supported.
__func__ is a string variable containing the current
function name.
__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.
struct { int x, y; } st[10] = { [0].x = 1, [0].y = 2 };
int tab[10] = { 1, 2, [5] = 5, [9] = 9};
int *p = (int []){ 1, 2, 3 };
to initialize a pointer pointing to an initialized array. The same
works for structures and strings.
double d = 0x1234p10;
is the same as writing
double d = 4771840.0;
inline keyword is ignored.
restrict keyword is ignored.
TCC implements some GNU C extensions:
int a[10] = { [0] 1, [5] 2, 3, 4 };
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.
cases:
switch(a) {
case 1 ... 9:
printf("range 1 to 9\n");
break;
default:
printf("unexpected\n");
break;
}
__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.
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.
#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).
__alignof__ keyword can be used as sizeof
to get the alignment of a type or an expression.
typeof(x) returns the type of x.
x is an expression or a type.
&&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.
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.
__TINYC__ is a predefined macro to 1 to
indicate that you use TCC.
#! at the start of a line is ignored to allow scripting.
0b101 instead of
5).
__BOUNDS_CHECKING_ON is defined if bound checking is activated.
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.
TinyCC Assembler supports most of the gas syntax. The tokens are the same as C.
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:
All directives are preceeded by a '.'. The following directives are supported:
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.
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.
TCC can load ELF object files, archives (.a files) and dynamic libraries (.so).
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.
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 )
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:
{
char tab[10];
memset(tab, 0, 11);
}
{
int tab[10];
for(i=0;i<11;i++) {
sum += tab[i];
}
}
{
int *tab;
tab = malloc(20 * sizeof(int));
for(i=0;i<21;i++) {
sum += tab4[i];
}
free(tab);
}
{
int *tab;
tab = malloc(20 * sizeof(int));
free(tab);
for(i=0;i<20;i++) {
sum += tab4[i];
}
}
{
int *tab;
tab = malloc(20 * sizeof(int));
free(tab);
free(tab);
}
libtcc library
The libtcc library enables you to use TCC as a backend for
dynamic code generation.
Read the `libtcc.h' to have an overview of the API. Read `libtcc_test.c' to have a very simple example.
The idea consists in giving a C string containing the program you want
to compile directly to libtcc. Then you can access to any global
symbol (function or variable) defined.
This chapter gives some hints to understand how TCC works. You can skip it if you do not intend to modify the TCC code.
The BufferedFile structure contains the context needed to read a
file, including the current line number. tcc_open() opens a new
file and tcc_close() closes it. inp() returns the next
character.
next() reads the next token in the current
file. next_nomacro() reads the next token without macro
expansion.
tok contains the current token (see TOK_xxx)
constants. Identifiers and keywords are also keywords. tokc
contains additional infos about the token (for example a constant value
if number or string token).
The parser is hardcoded (yacc is not necessary). It does only one pass, except:
The types are stored in a single 'int' variable. It was choosen in the first stages of development when tcc was much simpler. Now, it may not be the best solution.
#define VT_INT 0 /* integer type */
#define VT_BYTE 1 /* signed byte type */
#define VT_SHORT 2 /* short type */
#define VT_VOID 3 /* void type */
#define VT_PTR 4 /* pointer */
#define VT_ENUM 5 /* enum definition */
#define VT_FUNC 6 /* function type */
#define VT_STRUCT 7 /* struct/union definition */
#define VT_FLOAT 8 /* IEEE float */
#define VT_DOUBLE 9 /* IEEE double */
#define VT_LDOUBLE 10 /* IEEE long double */
#define VT_BOOL 11 /* ISOC99 boolean type */
#define VT_LLONG 12 /* 64 bit integer */
#define VT_LONG 13 /* long integer (NEVER USED as type, only
during parsing) */
#define VT_BTYPE 0x000f /* mask for basic type */
#define VT_UNSIGNED 0x0010 /* unsigned type */
#define VT_ARRAY 0x0020 /* array type (also has VT_PTR) */
#define VT_BITFIELD 0x0040 /* bitfield modifier */
#define VT_STRUCT_SHIFT 16 /* structure/enum name shift (16 bits left) */
When a reference to another type is needed (for pointers, functions and
structures), the 32 - VT_STRUCT_SHIFT high order bits are used to
store an identifier reference.
The VT_UNSIGNED flag can be set for chars, shorts, ints and long
longs.
Arrays are considered as pointers VT_PTR with the flag
VT_ARRAY set.
The VT_BITFIELD flag can be set for chars, shorts, ints and long
longs. If it is set, then the bitfield position is stored from bits
VT_STRUCT_SHIFT to VT_STRUCT_SHIFT + 5 and the bit field size is stored
from bits VT_STRUCT_SHIFT + 6 to VT_STRUCT_SHIFT + 11.
VT_LONG is never used except during parsing.
During parsing, the storage of an object is also stored in the type integer:
#define VT_EXTERN 0x00000080 /* extern definition */ #define VT_STATIC 0x00000100 /* static variable */ #define VT_TYPEDEF 0x00000200 /* typedef definition */
All symbols are stored in hashed symbol stacks. Each symbol stack
contains Sym structures.
Sym.v contains the symbol name (remember
an idenfier is also a token, so a string is never necessary to store
it). Sym.t gives the type of the symbol. Sym.r is usually
the register in which the corresponding variable is stored. Sym.c is
usually a constant associated to the symbol.
Four main symbol stacks are defined:
define_stack
#defines).
global_stack
local_stack
global_label_stack
goto).
label_stack
__label__ keyword).
sym_push() is used to add a new symbol in the local symbol
stack. If no local symbol stack is active, it is added in the global
symbol stack.
sym_pop(st,b) pops symbols from the symbol stack st until
the symbol b is on the top of stack. If b is NULL, the stack
is emptied.
sym_find(v) return the symbol associated to the identifier
v. The local stack is searched first from top to bottom, then the
global stack.
The generated code and datas are written in sections. The structure
Section contains all the necessary information for a given
section. new_section() creates a new section. ELF file semantics
is assumed for each section.
The following sections are predefined:
text_section
data_section
bss_section
bounds_section
lbounds_section
stab_section
stabstr_section
symtab_section
strtab_section
The TCC code generator directly generates linked binary code in one pass. It is rather unusual these days (see gcc for example which generates text assembly), but it can be very fast and surprisingly little complicated.
The TCC code generator is register based. Optimization is only done at the expression level. No intermediate representation of expression is kept except the current values stored in the value stack.
On x86, three temporary registers are used. When more registers are needed, one register is spilled into a new temporary variable on the stack.
When an expression is parsed, its value is pushed on the value stack
(vstack). The top of the value stack is vtop. Each value
stack entry is the structure SValue.
SValue.t is the type. SValue.r indicates how the value is
currently stored in the generated code. It is usually a CPU register
index (REG_xxx constants), but additional values and flags are
defined:
#define VT_CONST 0x00f0 #define VT_LLOCAL 0x00f1 #define VT_LOCAL 0x00f2 #define VT_CMP 0x00f3 #define VT_JMP 0x00f4 #define VT_JMPI 0x00f5 #define VT_LVAL 0x0100 #define VT_SYM 0x0200 #define VT_MUSTCAST 0x0400 #define VT_MUSTBOUND 0x0800 #define VT_BOUNDED 0x8000 #define VT_LVAL_BYTE 0x1000 #define VT_LVAL_SHORT 0x2000 #define VT_LVAL_UNSIGNED 0x4000 #define VT_LVAL_TYPE (VT_LVAL_BYTE | VT_LVAL_SHORT | VT_LVAL_UNSIGNED)
VT_CONST
SValue.c, depending on its type.
VT_LOCAL
SValue.c.i in the
stack.
VT_CMP
SValue.c.i.
If any code is generated which destroys the CPU flags, this value MUST be
put in a normal register.
VT_JMP
VT_JMPI
|| and && logical
operators.
If any code is generated, this value MUST be put in a normal
register. Otherwise, the generated code won't be executed if the jump is
taken.
VT_LVAL
VT_LVAL is very important if you want to
understand how TCC works.
VT_LVAL_BYTE
VT_LVAL_SHORT
VT_LVAL_UNSIGNED
VT_LLOCAL
VT_LLOCAL should be eliminated
ASAP because its semantics are rather complicated.
VT_MUSTCAST
VT_SYM
SValue.sym must be added to the constant.
VT_MUSTBOUND
VT_BOUNDED
vsetc() and vset() pushes a new value on the value
stack. If the previous vtop was stored in a very unsafe place(for
example in the CPU flags), then some code is generated to put the
previous vtop in a safe storage.
vpop() pops vtop. In some cases, it also generates cleanup
code (for example if stacked floating point registers are used as on
x86).
The gv(rc) function generates code to evaluate vtop (the
top value of the stack) into registers. rc selects in which
register class the value should be put. gv() is the most
important function of the code generator.
gv2() is the same as gv() but for the top two stack
entries.
See the `i386-gen.c' file to have an example.
load()
store()
gfunc_start()
gfunc_param()
gfunc_call()
gfunc_prolog()
gfunc_epilog()
gen_opi(op)
gen_opf(op)
gen_opi() for floating point operations. The two top
entries of the stack are guaranted to contain floating point values of
same types.
gen_cvt_itof()
gen_cvt_ftoi()
gen_cvt_ftof()
gen_bounded_ptr_add()
gen_bounded_ptr_deref()
Constant propagation is done for all operations. Multiplications and divisions are optimized to shifts when appropriate. Comparison operators are optimized by maintaining a special cache for the processor flags. &&, || and ! are optimized by maintaining a special 'jump target' value. No other jump optimization is currently performed because it would require to store the code in a more abstract fashion.
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