python-cc 0.0.5

Pcc is a c compiler built on python and llvm.

Pcc

What is this?

Pcc is a C compiler based on ply + pycparser + llvmlite + llvm. We can run C programs like Python: pcc test.c to run C code. Pcc was inspired by: https://github.com/eliben/pykaleidoscope.

Notice

1. Some code skeleton comes from pykaleidoscope.
2. ply and pycparser are embedded into this project for debug use.

Install

pip install python-cc

This gives you the pcc command:

pcc hello.c                        # compile and run
pcc myproject/                     # compile all .c files in directory
pcc --llvmdump test.c              # dump LLVM IR
pcc myproject/ -- arg1 arg2        # pass args to compiled program

Development

Requires Python 3.13+ and uv.

uv sync          # install dependencies
uv run pytest    # run all 500+ tests

Multi-file projects: put .c and .h files in a directory, one .c must contain main(). Pcc auto-discovers all .c files, merges them, and compiles.

Lua Compilation Goal

The target is to compile and run Lua 5.5.0 using pcc.

projects/lua-5.5.0/         - Lua 5.5.0 source code + Makefile
projects/lua-5.5.0/testes/  - Lua test suite

Test Structure

Tests in tests/test_lua.py compare three builds:

Build	Method
pcc	onelua.c → pcc preprocess/parse/codegen → LLVM IR → cc compile+link
native	onelua.c → cc -O0 single-file compile
makefile	make with project Makefile (separate compilation of each .c, static lib + link)

# Run all Lua tests (~25s with auto workers)
uv run pytest tests/test_lua.py -v

# Individual file compilation through pcc pipeline
uv run pytest tests/test_lua.py::test_lua_source_compile -v
# pcc vs native (same onelua.c, test pcc as C compiler)
uv run pytest tests/test_lua.py::test_pcc_runtime_matches_native -v
# pcc vs Makefile-built lua (official reference)
uv run pytest tests/test_lua.py::test_pcc_runtime_matches_makefile -v
# Lua test suite with Makefile-built binary (baseline)
uv run pytest tests/test_lua.py::test_makefile_lua_test_suite -v

Note: heavy.lua is excluded from automated tests (runs ~2 min+, may timeout). Run manually:

# Build Makefile lua, then run heavy.lua directly
cd projects/lua-5.5.0 && make CC=cc CWARNS= MYCFLAGS="-std=c99 -DLUA_USE_MACOSX" MYLDFLAGS= MYLIBS=
./lua testes/heavy.lua

Add C test cases

# Single file: add to c_tests/ with expected return value
echo '// EXPECT: 42
int main(){ return 42; }' > c_tests/mytest.c

# Multi-file project: create a directory with main.c
mkdir c_tests/myproject
# ... add .c and .h files, main.c must have: // EXPECT: N

# Run all C file tests
uv run pytest tests/test_c_files.py -v

Preprocessor

#include <stdio.h>          // system headers: 133 libc functions auto-declared
#include "mylib.h"          // user headers: read and inline file content
#define MAX_SIZE 100        // object-like macro
#define MAX(a,b) ((a)>(b)?(a):(b))  // function-like macro
#define DEBUG               // flag for conditional compilation
#ifdef / #ifndef / #if / #elif / #else / #endif  // conditional compilation
#if defined(X) && (VERSION >= 3)  // expression evaluation with defined()
#undef NAME                 // undefine macro

Built-in macros: NULL, EOF, EXIT_SUCCESS, EXIT_FAILURE, RAND_MAX, INT_MAX, INT_MIN, LLONG_MAX, CHAR_BIT, true, false, __STDC__

Built-in typedefs: size_t, ssize_t, ptrdiff_t, va_list, FILE, time_t, clock_t, pid_t

Supported C Features

Types

int, double, float, char, void, unsigned/signed/long/short (all combinations), size_t, int8_t..uint64_t, pointers (multi-level), arrays (multi-dim), structs (named, anonymous, nested, with array/pointer/function-pointer members, pointer-to-struct), unions, enums (with constant expressions), typedef (scalar, struct, pointer, function pointer), static local variables, const/volatile qualifiers

Operators

• Arithmetic: + - * / %
• Bitwise: & | ^ << >>
• Comparison: < > <= >= == != (including pointer comparison)
• Logical: && || (short-circuit evaluation)
• Unary: -x +x !x ~x sizeof &x *p
• Increment/Decrement: ++x x++ --x x-- (int and pointer, including struct members)
• Assignment: = += -= *= /= %= <<= >>= &= |= ^= (including pointer +=/-=)
• Ternary: a ? b : c
• Pointer: p + n, p - n, p - q, p++, p[i]
• Struct access: . and -> (including nested a.b.c and s->fn(args))
• Chained: a = b = c = 5

Control Flow

if / else / else if, while, do-while, for (all variants including for(;;)), switch / case / default, goto / label, break, continue, return

Functions

Definitions, forward declarations, mutual recursion, void functions, variadic (...), pointer/array arguments, static local variables, function pointers (declaration, assignment, calling, as parameters, in structs, typedef'd), callback patterns

Libc Functions (133 total, auto-declared on first use)

Header	Functions
stdio.h	printf, fprintf, sprintf, snprintf, puts, putchar, getchar, fopen, fclose, fread, fwrite, fseek, ftell, fgets, fputs, scanf, sscanf, ...
stdlib.h	malloc, calloc, realloc, free, abs, labs, atoi, atol, atof, strtol, strtod, rand, srand, exit, abort, qsort, bsearch, getenv, system, ...
string.h	strlen, strcmp, strncmp, strcpy, strncpy, strcat, strncat, strchr, strrchr, strstr, memset, memcpy, memmove, memcmp, memchr, strtok, ...
ctype.h	isalpha, isdigit, isalnum, isspace, isupper, islower, isprint, ispunct, isxdigit, toupper, tolower, ...
math.h	sin, cos, tan, asin, acos, atan, atan2, exp, log, log2, log10, pow, sqrt, cbrt, hypot, ceil, floor, round, trunc, fmod, fabs, ...
time.h	time, clock, difftime
unistd.h	sleep, usleep, read, write, open, close, getpid, getppid
setjmp.h	setjmp, longjmp
signal.h	signal, raise

Literals

Decimal, hex (0xFF), octal (077), char ('a', '\n'), string ("hello\n"), double (3.14)

Other

C comments (/* */, //), array initializer lists (1D and multi-dim), string escape sequences (\n \t \\ \0 \r), implicit type promotion (int/char/double/pointer), array-to-pointer decay, NULL pointer support, opaque/forward-declared structs, two-pass codegen (types first, functions second)