This manual documents version 0.9.28rc of the Tiny C Compiler.
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 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 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.
For usage on Windows, see also tcc-win32.txt.
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.
‘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;
}
TCC can read C source code from standard input when - is used in place of infile. Example:
echo 'main(){puts("hello");}' | tcc -run -
General Options:
Generate an object file.
Put object file, executable, or dll into output file outfile.
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:
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
Display TCC version.
Show included files. As sole argument, print search dirs. -vvv shows tries too.
Display compilation statistics.
Preprocessor options:
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).
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
Undefine preprocessor symbol ‘sym’.
Preprocess only, to stdout or file (with -o).
Compilation flags:
Note: each of the following options has a negative form beginning with -fno-.
Let the char type be unsigned.
Let the char type be signed.
Do not generate common symbols for uninitialized data.
Add a leading underscore at the beginning of each C symbol.
Allow a MS C compiler extensions to the language. Currently this assumes a nested named structure declaration without an identifier behaves like an unnamed one.
Allow dollar signs in identifiers
Create code coverage code. After running the resulting code an executable.tcov or sofile.tcov file is generated with code coverage.
Warning options:
Disable all warnings.
Note: each of the following warning options has a negative form beginning with -Wno-.
Warn about implicit function declaration.
Warn about unsupported GCC features that are ignored by TCC.
Make string constants be of type const char * instead of char
*.
Abort compilation if a warning is issued. Can be given an option to enable the specified warning and turn it into an error, for example -Werror=unsupported.
Activate some useful warnings.
Linker options:
Specify an additional static library path for the -l option. The default library paths are /usr/local/lib, /usr/lib and /lib.
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 and LIBRARY_PATH variable.
Set the path where the tcc internal libraries (and include files) can be found (default is PREFIX/lib/tcc).
Generate a shared library instead of an executable.
set name for shared library to be used at runtime
Generate a statically linked executable (default is a shared linked executable).
Export global symbols to the dynamic linker. It is useful when a library
opened with dlopen() needs to access executable symbols.
Generate an object file combining all input files.
Put custom search path for dynamic libraries into executable.
When putting a custom search path for dynamic libraries into the executable, create the new ELF dynamic tag DT_RUNPATH instead of the old legacy DT_RPATH.
Use fmt as output format. The supported output formats are:
elf32-i386ELF output format (default)
binaryBinary image (only for executable output)
coffCOFF output format (only for executable output for TMS320C67xx target)
Export global symbols to the dynamic linker. It is useful when a library
opened with dlopen() needs to access executable symbols.
Set type for PE (Windows) executables.
Modify executable layout.
Set DT_SYMBOLIC tag.
Turn on/off linking of all objects in archives.
Debugger options:
Generate run time stab 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.
Generate run time dwarf debug information instead of stab debug information.
Generate additional support code to check memory allocations and array/pointer bounds (see TinyCC Memory and Bound checks). -g is implied.
Display N callers in stack traces. This is useful with -g or -b.
When activated, __TCC_BACKTRACE__ is defined.
With executables, additional support for stack traces is included. A function
int tcc_backtrace(const char *fmt, ...);
is provided to trigger a stack trace with a message on demand.
Misc options:
Just output makefile fragment with dependencies
Like -M except mention only user header files, not system header files.
Generate makefile fragment with dependencies.
Like -MD except mention only user header files, not system header files.
Use depfile as output for -MD.
Print the configured installation directory and a list of library and include directories tcc will search.
Print version.
Target specific options:
Use an algorithm for bitfield alignment consistent with MSVC. Default is gcc’s algorithm.
Select the float ABI. Possible values: softfp and hard
Do not use sse registers on x86_64
Pass command line to the i386/x86_64 cross compiler.
Note: GCC options -Ox, -fx and -mx are ignored.
Environment variables that affect how tcc operates.
A colon-separated list of directories searched for include files, directories given with -I are searched first.
A colon-separated list of directories searched for libraries for the -l option, directories given with -L are searched first.
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.
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.
dllexport: export function from dll/executable (win32 only)
nodecorate: do not apply any decorations that would otherwise be applied when exporting function from dll/executable (win32 only)
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.
#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 indicate that you use TCC.
#! at the start of a line is ignored to allow scripting.
0b101 instead of
5).
Since version 0.9.16, TinyCC integrates its own assembler. TinyCC assembler supports a gas-like syntax (GNU assembler). You can deactivate 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 preceded 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 EXE files (console and gui) and DLL files.
For usage on Windows, see also tcc-win32.txt.
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 option (see Command line invocation). 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 += tab[i];
}
free(tab);
}
{
int *tab;
tab = malloc(20 * sizeof(int));
free(tab);
for(i=0;i<20;i++) {
sum += tab[i];
}
}
{
int *tab;
tab = malloc(20 * sizeof(int));
free(tab);
free(tab);
}
TCC defines __TCC_BCHECK__ if activated.
There are five environment variables that can be used to control the behavior:
Also, a function __bounds_checking(x) can be used to turn off/on bounds
checking from usercode (see below).
Notes:
#ifdef __TCC_BCHECK__ extern void __bounds_checking (int x); # define BOUNDS_CHECKING_OFF __bounds_checking(1) # define BOUNDS_CHECKING_ON __bounds_checking(-1) #else # define BOUNDS_CHECKING_OFF # define BOUNDS_CHECKING_ON #endif
For more information about the ideas behind this method, see http://www.doc.ic.ac.uk/~phjk/BoundsChecking.html.
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 chosen 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_VLA 0x20000 /* VLA type (also has VT_PTR and VT_ARRAY) */
#define VT_BITFIELD 0x0040 /* bitfield modifier */
#define VT_CONSTANT 0x0800 /* const modifier */
#define VT_VOLATILE 0x1000 /* volatile modifier */
#define VT_DEFSIGN 0x2000 /* signed type */
#define VT_STRUCT_SHIFT 18 /* structure/enum name shift (14 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. Variable length arrays are considered as special
arrays and have flag VT_VLA set instead of VT_ARRAY.
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 */ #define VT_INLINE 0x00000400 /* inline definition */ #define VT_IMPORT 0x00004000 /* win32: extern data imported from dll */ #define VT_EXPORT 0x00008000 /* win32: data exported from dll */ #define VT_WEAK 0x00010000 /* win32: data exported from dll */
All symbols are stored in hashed symbol stacks. Each symbol stack
contains Sym structures.
Sym.v contains the symbol name (remember
an identifier 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 like its address for normal
symbols, and the number of entries for symbols representing arrays.
Variable length array types use Sym.c as a location on the stack
which holds the runtime sizeof for the type.
Four main symbol stacks are defined:
define_stackfor the macros (#defines).
global_stackfor the global variables, functions and types.
local_stackfor the local variables, functions and types.
global_label_stackfor the local labels (for goto).
label_stackfor GCC block local labels (see the __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 data 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_sectionis the section containing the generated code. ind contains the current position in the code section.
data_sectioncontains initialized data
bss_sectioncontains uninitialized data
bounds_sectionlbounds_sectionare used when bound checking is activated
stab_sectionstabstr_sectionare used when debugging is active to store debug information
symtab_sectionstrtab_sectioncontain the exported symbols (currently only used for debugging).
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_CONSTindicates that the value is a constant. It is stored in the union
SValue.c, depending on its type.
VT_LOCALindicates a local variable pointer at offset SValue.c.i in the
stack.
VT_CMPindicates that the value is actually stored in the CPU flags (i.e. the
value is the consequence of a test). The value is either 0 or 1. The
actual CPU flags used is indicated in SValue.c.i.
If any code is generated which destroys the CPU flags, this value MUST be put in a normal register.
VT_JMPVT_JMPIindicates that the value is the consequence of a conditional jump. For VT_JMP, it is 1 if the jump is taken, 0 otherwise. For VT_JMPI it is inverted.
These values are used to compile the || 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_LVALis a flag indicating that the value is actually an lvalue (left value of an assignment). It means that the value stored is actually a pointer to the wanted value.
Understanding the use VT_LVAL is very important if you want to
understand how TCC works.
VT_LVAL_BYTEVT_LVAL_SHORTVT_LVAL_UNSIGNEDif the lvalue has an integer type, then these flags give its real type. The type alone is not enough in case of cast optimisations.
VT_LLOCALis a saved lvalue on the stack. VT_LVAL must also be set with
VT_LLOCAL. VT_LLOCAL can arise when a VT_LVAL in
a register has to be saved to the stack, or it can come from an
architecture-specific calling convention.
VT_MUSTCASTindicates that a cast to the value type must be performed if the value is used (lazy casting).
VT_SYMindicates that the symbol SValue.sym must be added to the constant.
VT_MUSTBOUNDVT_BOUNDEDare only used for optional bound checking.
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()must generate the code needed to load a stack value into a register.
store()must generate the code needed to store a register into a stack value lvalue.
gfunc_start()gfunc_param()gfunc_call()should generate a function call
gfunc_prolog()gfunc_epilog()should generate a function prolog/epilog.
gen_opi(op)must generate the binary integer operation op on the two top entries of the stack which are guaranteed to contain integer types.
The result value should be put on the stack.
gen_opf(op)same as gen_opi() for floating point operations. The two top
entries of the stack are guaranteed to contain floating point values of
same types.
gen_cvt_itof()integer to floating point conversion.
gen_cvt_ftoi()floating point to integer conversion.
gen_cvt_ftof()floating point to floating point of different size conversion.
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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