Naive C-like Compiler

The code is derived from my compiler lab code in school. Since the lab only covers some basic topics of a compiler, and my implementation is dirty and naive, I want to keep polishing my code and present my work here.

Supported Syntax

Some significant limitations are shown below:

1. No declaration, all functions should be defined before called;
2. No global variables (parsed but cannot generate code);
3. No preprocessor;
4. Basic type only consists of int (float is parsed but cannot generate code);
5. All local variables should be defined at the beginning of a function;
6. Struct is passed by reference, and returning a struct is dangerous.

The top level of a program should look like this:

// one-line comment

/**
 * multi-line comment
 * can be /* nested */
 * ignore everything after //
 * like // */
 * like // /*
 * like // *//*
 * like // /*_*/
 */ // This is the end of this multi-line commet!

// int read()
// write(int x)
// are provided functions to support input and output

int echo(int e)
{
    write(e);
    return read();
}

struct A {
    int a;
    int b;
};

int main()
{
    /* Local definitions, like follows */

    int foo;
    int bar = 3;
    int vec[2];
    struct A a;

    /* Statements, like follows */

    if (/* Expression */) {
        /* Statements */
    }
    else if (/* Expression */) {
        /* Statements */
    }
    else {
        /* Statements */
    }

    while (/* Expression */) {
        /* Statements */
    }

    // the three parts of for-loop cannot be omitted currently
    for (foo = 0; foo < 10; foo = foo + 1) {
        write(foo);
    }

    /* Expressions */

    foo = bar;  // Assignment
    foo + 1;    // Binary operation: +, -, *, /
    foo < bar;  // Comparing operation: <, <=, >, >=, ==, !=
    !foo;       // Unary operation: -, !
    a.a         // field access
    (foo);
    foo = echo(vec[0]);  // Function call, array access

    return 0;
}