Tiny, self-contained C compiler using TCC + uClibc

This post presents how I played with a small C compiler and a small libc on Linux. I've combined TCC (the Tiny C Compiler) 0.9.25 and uClibc 0.9.26, compressed with UPX 3.03 to a tiny, self-contained C compiler for Linux i386. You don't need any external files (apart from the compiler executable) to compile (or interpret) C code, and the compiled executable will be self-contained as well.

Here is how to download and use it for compilation on a Linux x86 or x86_64 system:

$ uname
Linux
$ wget -O pts-tcc https://raw.githubusercontent.com/pts/pts-tcc/master/pts-tcc-0.9.26-uclibc-0.9.30.1
$ chmod +x pts-tcc
$ ls -l pts-tcc
-rwxrwxr-- 1 pts pts 349640 Nov  1 13:07 pts-tcc
$ wget -O example1.c https://raw.githubusercontent.com/pts/pts-tcc/master/pts-tcc/example1.c
$ cat example1.c
#! ./pts-tcc -run
int printf(char const*fmt, ...);
double sqrt(double x);
int main() {
  printf("Hello, World!\n");
  return sqrt(36) * 7;
}
$ ./pts-tcc example1.c
$ file a.out
a.out: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), statically linked, not stripped
$ ls -l a.out
-rwxrwxr-x 1 pts pts 17124 Nov  1 13:17 a.out
$ ./a.out; echo "$?"
Hello, World!
42
$ strace -e open ./pts-tcc example1.c
open("/proc/self/mem", O_RDONLY)        = 3
open("/proc/self/mem", O_RDONLY)        = 3
open("example1.c", O_RDONLY)            = 3
open("/proc/self/mem", O_RDONLY)        = 3
open("/proc/self/mem", O_RDONLY)        = 3
open("a.out", O_WRONLY|O_CREAT|O_TRUNC, 0777) = 3
$ strace ./a.out
execve("./a.out", ["./a.out"], [/* 47 vars */]) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
write(1, "Hello, World!\n", 14Hello, World!
)         = 14
_exit(42)                               = ?

As you can see above, my version the compiler is less than 250k in size, and it doesn't need any library files (such as libc.so) for compilation (as indicated by the strace output above), and the compiled binary doesn't need library files either.

TCC can run the C program without creating any binaries:

$ rm -f a.out
$ ./pts-tcc -run example1.c; echo "$?"
Hello, World!
42
$ head -1 example1.c
#! ./pts-tcc -run
$ chmod +x example1.c
$ ./example1.c; echo "$?"
Hello, World!

TCC is a very fast compiler (see the speed comparisons on it web site), it is versatile (it can compile the Linux kernel), but it doesn't optimize much: the code it produces is usually larger and slower than the output of a traditional, optimizing C compiler such as gcc -O2.

The shell script pts-tcc-0.9.26-compile.sh builds TCC from source, adding uClibc, and compressing with UPX.

Update: TCC 0.9.25 and uClibc 0.9.29 (or older)

Please note that TCC 0.9.25 is buggy, don't use it!

$ wget -O pts-tcc https://raw.githubusercontent.com/pts/pts-tcc/master/pts-tcc/pts-tcc-0.9.25
$ chmod +x pts-tcc
$ ls -l pts-tcc
-rwxr-xr-x 1 pts eng 241728 Apr  8 16:53 pts-tcc

Update: TCC 0.9.25 and uClibc 0.9.30.1

Please note that TCC 0.9.25 is buggy, don't use it!

$ wget -O pts-tcc https://raw.githubusercontent.com/pts/pts-tcc/master/pts-tcc-0.9.25-uclibc-0.9.30.1
$ chmod +x pts-tcc
$ ls -l pts-tcc
-rwxr-xr-x 1 pts eng 336756 Apr  8 16:53 pts-tcc

Update: TCC 0.9.26 and uClibc 0.9.30.1

$ wget -O pts-tcc https://raw.githubusercontent.com/pts/pts-tcc/master/pts-tcc-0.9.26-uclibc-0.9.30.1
$ chmod +x pts-tcc
$ ls -l pts-tcc
-rwxr-xr-x 1 pts eng 349640 Apr  8 16:53 pts-tcc