forked from Mirrors/tinycc
d242706f3b
bit_pos + bit_size > type_size * 8
must NEVER happen because the code generator can read/write
only the basic integral types.
Warn if tcc has to break GCC compatibility for that reason
and if -Wgcc-compat is given.
Example:
struct __attribute__((packed)) _s
{
unsigned int x : 12;
unsigned char y : 7;
unsigned int z : 28;
};
Expected (GCC) layout (sizeof struct = 6)
.xxxxxxxx.xxxxyyyy.yyyzzzzz.zzzzzzzz.zzzzzzzz.zzzzzzz0.
But we cannot read/write 'char y'from 2 bytes in memory.
So we have to adjust:
.xxxxxxxx.xxxx0000.yyyyyyyz.zzzzzzzz.zzzzzzzz.zzzzzzzz.zzz00000
Now 'int z' cannot be accessed from 5 bytes. So we arrive
at this (sizeof struct = 7):
.xxxxxxxx.xxxx0000.yyyyyyy0.zzzzzzzz.zzzzzzzz.zzzzzzzz.zzzz0000
Otherwise the bitfield load/store generator needs to be
changed to allow byte-wise accesses.
Also we may touch memory past the struct in some cases
currently. The patch adds a warning for that too.
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 81 ec 04 00 00 00 sub $0x4,%esp
9: 90 nop
struct __attribute__((packed)) { unsigned x : 5; } b = {0} ;
a: 8b 45 ff mov -0x1(%ebp),%eax
d: 83 e0 e0 and $0xffffffe0,%eax
10: 89 45 ff mov %eax,-0x1(%ebp)
This touches -0x1 ... +0x3(%ebp), hence 3 bytes beyond
stack space. Since the data is not changed, nothing
else happens here.
|
||
|---|---|---|
| examples | ||
| include | ||
| lib | ||
| tests | ||
| win32 | ||
| .gitignore | ||
| COPYING | ||
| Changelog | ||
| CodingStyle | ||
| Makefile | ||
| README | ||
| RELICENSING | ||
| TODO | ||
| VERSION | ||
| arm-asm.c | ||
| arm-gen.c | ||
| arm-link.c | ||
| arm64-gen.c | ||
| arm64-link.c | ||
| c67-gen.c | ||
| c67-link.c | ||
| coff.h | ||
| configure | ||
| conftest.c | ||
| elf.h | ||
| i386-asm.c | ||
| i386-asm.h | ||
| i386-gen.c | ||
| i386-link.c | ||
| i386-tok.h | ||
| il-gen.c | ||
| il-opcodes.h | ||
| libtcc.c | ||
| libtcc.h | ||
| stab.def | ||
| stab.h | ||
| tcc-doc.texi | ||
| tcc.c | ||
| tcc.h | ||
| tccasm.c | ||
| tcccoff.c | ||
| tccelf.c | ||
| tccgen.c | ||
| tcclib.h | ||
| tccpe.c | ||
| tccpp.c | ||
| tccrun.c | ||
| tcctok.h | ||
| tcctools.c | ||
| texi2pod.pl | ||
| x86_64-asm.h | ||
| x86_64-gen.c | ||
| x86_64-link.c | ||
README
Tiny C Compiler - C Scripting Everywhere - The Smallest ANSI C compiler ----------------------------------------------------------------------- Features: -------- - SMALL! You can compile and execute C code everywhere, for example on rescue disks. - FAST! tcc generates optimized x86 code. No byte code overhead. Compile, assemble and link about 7 times faster than 'gcc -O0'. - UNLIMITED! Any C dynamic library can be used directly. TCC is heading torward full ISOC99 compliance. TCC can of course compile itself. - SAFE! tcc includes an optional memory and bound checker. Bound checked code can be mixed freely with standard code. - Compile and execute C source directly. No linking or assembly necessary. Full C preprocessor included. - C script supported : just add '#!/usr/local/bin/tcc -run' at the first line of your C source, and execute it directly from the command line. Documentation: ------------- 1) Installation on a i386/x86_64/arm Linux/OSX/FreeBSD host ./configure make make test make install Notes: For OSX and FreeBSD, gmake should be used instead of make. For Windows read tcc-win32.txt. makeinfo must be installed to compile the doc. By default, tcc is installed in /usr/local/bin. ./configure --help shows configuration options. 2) Introduction We assume here that you know ANSI C. Look at the example ex1.c to know what the programs look like. The include file <tcclib.h> can be used if you want a small basic libc include support (especially useful for floppy disks). Of course, you can also use standard headers, although they are slower to compile. You can begin your C script with '#!/usr/local/bin/tcc -run' on the first line and set its execute bits (chmod a+x your_script). Then, you can launch the C code as a shell or perl script :-) The command line arguments are put in 'argc' and 'argv' of the main functions, as in ANSI C. 3) Examples ex1.c: simplest example (hello world). Can also be launched directly as a script: './ex1.c'. ex2.c: more complicated example: find a number with the four operations given a list of numbers (benchmark). ex3.c: compute fibonacci numbers (benchmark). ex4.c: more complicated: X11 program. Very complicated test in fact because standard headers are being used ! As for ex1.c, can also be launched directly as a script: './ex4.c'. ex5.c: 'hello world' with standard glibc headers. tcc.c: TCC can of course compile itself. Used to check the code generator. tcctest.c: auto test for TCC which tests many subtle possible bugs. Used when doing 'make test'. 4) Full Documentation Please read tcc-doc.html to have all the features of TCC. Additional information is available for the Windows port in tcc-win32.txt. License: ------- TCC is distributed under the GNU Lesser General Public License (see COPYING file). Fabrice Bellard.