rcc

Join us on Discord

rcc: a Rust C compiler

A C compiler written in Rust, with a focus on good error messages. Warning: my first rust project, code quality is pretty low.

Running

rcc reads from standard in by default, so you can type in code directly. It's not interactive though, you have to hit Ctrl+D to indicate end of file (Ctrl+Z on Windows).

Use rcc --help for all options (or see below).

Running on Windows

You need to have cc on your PATH. You can either install mingw + gcc or MSVC. Other than that, it should work exactly the same as on Linux.

TODO

• Complex assignment (a /= 5)
• Multiple translation units (files)
• Bitfields?
• Compile on non-x86 platforms
• Cross-compile

Examples

$ cat tests/runner-tests/readme.c
// output: j is 6
int printf(const char *, ...);

typedef struct s *sp;

int i = 1;
int a[3] = {1, 2, 3};
float f = 2.5;

struct s {
  int outer;
} my_struct;

int g(int);

int main(void) {
  sp my_struct_pointer = &my_struct;
  const int c = my_struct_pointer->outer = 4;
  // should return 6
  int j = i + f*a[2] - c/g(1);
  printf("j is %d\n", j);
  return j;
}

int g(int i) {
  if (i < 0 || i >= 3) {
    return 0;
  }
  return a[i];
}
$ rcc tests/runner-tests/readme.c
$️ ./a.out
j is 6

Debug output

$ cat tests/runner-tests/cpp/if/defined.c
// code: 2

#define a
#define b

#if defined(a)
int i = 2;
#endif

#ifndef b
syntax error
#endif

# if defined b && defined(a)
    int main() { return i; }
#endif
$ rcc -E tests/runner-tests/cpp/if/defined.c
int i = 2 ; int main ( ) { return i ; }

$ echo 'int i = 1 + 2 ^ 3 % 5 / 2 & 1; int main(){}' | rcc --debug-ast
auto int i = (int)(((1) + (2)) ^ ((((3) % (5)) / (2)) & (1)));
extern int main() {
}

$ cat tests/runner-tests/hello_world.c
#include<stdio.h>
int main() {
    puts("Hello, world!");
}
$ rcc --debug-asm tests/runner-tests/hello_world.c
function u0:0() -> i32 system_v {
    gv0 = symbol colocated u1:3
    sig0 = (i64) -> i32 system_v
    fn0 = u0:26 sig0

block0:
    v0 = global_value.i64 gv0
    v1 = call fn0(v0)
    v2 = iconst.i32 0
    return v2
}
$ ./a.out
Hello, world!

All options

$ rcc --help
rcc 0.5.0
Joshua Nelson <[email protected]>:Graham Scheaffer <[email protected]>
A C compiler written in Rust, with a focus on good error messages.
Homepage: https://github.com/jyn514/rcc/

usage: rcc [FLAGS] [OPTIONS] [<file>]

FLAGS:
        --debug-asm        If set, print the intermediate representation of the program in addition to compiling
    -a, --debug-ast        If set, print the parsed abstract syntax tree in addition to compiling
        --debug-lex        If set, print all tokens found by the lexer in addition to compiling.
    -h, --help             Prints help information
    -c, --no-link          If set, compile and assemble but do not link. Object file is machine-dependent.
    -E, --preprocess-only  If set, preprocess only, but do not do anything else.
                            Note that preprocessing discards whitespace and comments.
                            There is not currently a way to disable this behavior.
    -V, --version          Prints version information

OPTIONS:
    -o, --output <output>    The output file to use. [default: a.out]
        --max-errors <max>   The maximum number of errors to allow before giving up.
                             Use 0 to allow unlimited errors. [default: 10]

ARGS:
    <file>    The file to read C source from. "-" means stdin (use ./- to read a file called '-').
              Only one file at a time is currently accepted. [default: -]

Testing

cargo test
# optionally, you can fuzz the compiler
# it may be more helpful to just `grep -R unimplemented src`, though

# libFuzzer/AFL
tests/fuzz.sh

# Honggfuzz:
# Running Honggfuzz locally requires some parameters to use it at its full potential,
# so it is probably a good idea to have a look here: https://github.com/rust-fuzz/honggfuzz-rs/blob/master/README.md
# and here: https://github.com/google/honggfuzz/blob/master/docs/USAGE.md
# we suggest the following:
HFUZZ_RUN_ARGS="--tmout_sigvtalrm --exit_upon_crash" tests/hfuzz.sh

FAQ

See FAQ.md

Implementation Defined Behavior

See IMPLEMENTATION_DEFINED.md

Contributing

See CONTRIBUTING.md. This also includes reporting bugs.