cbc/ToDo

- generate resolved AST
        - constant table
        - types
        - scope, frame
- integer literal
	- 1, 2, 3, ...
	- octal (010)
	- hex (0x1f)
	- 1U, 1L, 1UL
- character literal
	- 'c'
	- standard escape sequence ('\n', ...)
	- octal escape sequence ('\077')
- string literal
	- "string"
	- standard escape sequence ('\n', ...)
	- octal escape sequence ("\077")
- import
        - single import
        - recursive import
        - import function
        - import type
- build x86 test environment
- compile "Hello, World"
- write unit tests
- funcall
        - 0 arg
        - 1 arg
        - 2 args
        - 3
        - 4 - 10 args
- variables
        - param
                - reference
                - assign
        - lvar
                - assign
                - reference
                - initializer
        - common symbol
                - assign
                - reference
        - global variable
                - define
                - reference
                - assign
        - private common symbol
                - assign
                - reference
        - private global variable
                - define
                - assign
                - reference
        - function-static variable
                - assign
                - reference
                - initializer
- op
        - +
        - -
        - *
        - /
        - %
- bitwise op
        - ~
        - &
        - |
        - ^
        - >>
        - <<
- unary op
        - +@
        - -@
        - !
- comparison op
        - ==
        - !=
        - >
        - >=
        - <
        - <=
- self assignment
        - +=, -=, *=, ...
        - ++
        - --
- control structure
        - if
        - while
                - flow
                - break
                - continue
        - for
                - flow
                - break
                - continue
        - do...while
                - flow
                - break
                - continue
        - switch
        - goto
- valued control structure
        - &&
        - ||
        - a ? b : c
- array
        - as LHS
        - as RHS
        - reject negative length array definition
- struct
        - as LHS
        - as RHS
        - recursive definition with pointer
- union
        - as LHS
        - as RHS
        - recursive definition with pointer
* composite literal {1,2,3...}
        - parse (initializer)
        - parse (rhs)
        * type check
        * code generation
- pointer
        - *ptr
        - *ptr = val
        - ptr->memb
        - ptr->memb = val
- &expr
        - as RHS
        * ?? as LHS
- function pointer
        - refer
        - call ptr(arg)
* complex LHS
        - local variable
        * parameter
        * global variables / common symbols
        * static variables
        * *arr[0] = ...
        * *st.memb = ...
        * *ptr++ = ...
        * *(ptr + N) = ...
        * *(int*)ptr = ...
        * their combination
- bare block ({...})
- cast
- semantic check (control)
        - reject break from out of loop/switch
        - reject continue from out of loop
        * reject no return
- semantic check (reference)
        - check all symbols are resolved
        - check duplicated parameters
        - check if the calling function exists
        - warn unused static variables
        - warn unused local variables
        - warn unused static functions
        - check if aref base expr is indexable (a must be indeable where a[0])
        - check if funcall base expr is callable (a must be callable where a())
* semantic check (type)
        - simple type check (binary ops, unary ops)
        - a[0]
        - *ptr
        - ct.memb
        - ptr->memb
        - funcall args
        - prohibit circular struct/union definition
        - implicit cast
        - validate struct/union member (ct.memb)
        - validate struct/union member (ct->memb)
        * check duplicated struct/union members
        * ptr + int; ptr - int
        * check return type
        * check if assignable
- op for various types
        - signed char
        - signed short
        - signed int
        - signed long
        - unsigned char
        - unsigned short
        - unsigned int
        - unsigned long
- Multibyte input
* print node location in error message
* parse command line option
* --dump-tokens
* --dump-ast
* ?? --dump-semantic
* generate IR
* --dump-ir
* control flow graph
* --dump-cflow
* semantic check (cflow)
        * warn unreachable stmt
        * warn no return
* data flow graph
* --dump-dflow
        * warn unused variable
        * warn uninitialized use of variables
* semantic check (dflow)
* register allocation
* vararg retrieve
* 64bit long_long support