set -e
__ESC="$(printf '\033.')"; __ESC="${__ESC%.}"
 __RS="$(printf '\036.')";  __RS="${__RS%.}"
 __US="$(printf '\037.')";  __US="${__US%.}"
__sp=0
__fn_name=
__fn_tu=
__fn_vars=
__fn_var_vals=
__fn=
__prev_tu=
__prev_vars=
__var=
__val=
__fn_frame=

__sp_inc()
{
	__sp=$((${__sp} + 1))
}

__sp_dec()
{
	__sp=$((${__sp} - 1))
}

__frame_set()
{
	eval "__frame_${__sp}_name=\${__fn_name}"
	eval "__frame_${__sp}_tu=\${__fn_tu}"
	eval "__frame_${__sp}_vars=\${__fn_vars}"
	eval "__frame_${__sp}_var_vals=\${__fn_var_vals}"
}

__frame_get()
{
	eval "__fn_name=\${__frame_${__sp}_name}"
	eval "__fn_tu=\${__frame_${__sp}_tu}"
	eval "__fn_vars=\${__frame_${__sp}_vars}"
	eval "__fn_var_vals=\${__frame_${__sp}_var_vals}"
}

__fn_ctxsw()
{
	unset IFS
	case "${__prev_tu}" in
		${__fn_tu});;
		?*)
			# Unset static variables and functions from previous TU.
			eval "unset \${__${__prev_tu}_static_vars}"
			eval "__val=\${__${__prev_tu}_static_fns}"
			for __fn in ${__val}; do
				unset -f "${__fn%:*}"
			done
	;; esac
	case "${__fn_tu}" in
		${__prev_tu});;
		?*)
			# Set static variables and function for the current TU.
			eval "__val=\${__${__fn_tu}_static_var_vals}"
			eval "${__val}"
			eval "__val=\${__${__fn_tu}_static_fns}"
			for __fn in ${__val}; do
				eval "${__fn%:*}() { ${__fn#*:}; }"
			done
	;; esac
	unset ${__prev_vars}
	eval "${__fn_var_vals}"
}

__fn_update_vars()
{
	for __var in ${__fn_vars}; do
		__val="$(eval "printf '%s' \"\${${__var}}\"" | \
			sed "s|'|'\\\\''|g;")"
		__fn_var_vals="${__fn_var_vals} ${__var}='${__val}'"
	done
}

__fn_start()
{
	# Old state.
	__prev_tu="${__fn_tu}"
	__prev_vars="${__fn_vars}"

	# Update local vars in stack.
	__fn_update_vars
	__frame_set

	# Set stack pointer.
	__sp_inc

	# New state.
	__fn_name="${2}"
	__fn_tu="${1}"
	__fn_vars=
	__fn_var_vals=
	__frame_set

	# Switch.
	__fn_ctxsw
}

__fn_end()
{
	# Old state.
	__prev_tu="${__fn_tu}"
	__prev_vars="${__fn_vars}"

	# Set stack pointer.
	__sp_dec

	# New state.
	__frame_get

	# Switch.
	__fn_ctxsw
}

__tu_end()
{
	# Save TU static vars.
	for __var in $(eval "printf '%s' \"\${__${__tu}_static_vars}\""); do
		__val="$(eval "printf '%s' \"\${${__var}}\"" | \
			sed "s|'|'\\\\''|g")"
		eval "__${__tu}_static_var_vals=\"\${__${__tu}_static_var_vals}\
			${__var}='\${__val}'\""
		unset ${__var}
	done

	__tu=''
}

__stack_trace()
{
	__fn_frame=0
	while [ ${__fn_frame} -le ${__sp} ]; do
		eval "printf '%s\n' \"\${__frame_${__fn_frame}_name}\""
		__fn_frame=$((${__fn_frame} + 1))
	done
}

__local()
{
	for __var in "${@}"; do
		case "${__var}" in
			*=*)
				__val="${__var#*=}"
				__var="${__var%%=*}"
				;;
			*)
				__val=''
				;;
		esac
		case "${__var}" in [!A-Za-z_]* | *[!0-9A-Za-z_]*)
			printf 'Syntax error: %s %s\n' \
				'illegal static variable name:' "${__var}" >&2
			exit 1
		;; esac
		eval "${__var}=\${__val}"
		__fn_vars="${__fn_vars} ${__var}"
	done
}

static()
{
	case "${__tu}" in '')
		printf 'Error: Cannot declare static variables in functions' >&2
		exit 1
	;; esac
	for __var in "${@}"; do
		case "${__var}" in
			*=*)
				__val="${__var#*=}"
				__var="${__var%%=*}"
				;;
			*)
				__val=''
				;;
		esac
		case "${__var}" in [!A-Za-z_]* | *[!0-9A-Za-z_]*)
			printf 'Syntax error: %s %s\n' \
				'illegal static variable name:' "${__var}" >&2
			exit 1
		;; esac
		eval "${__var}=\${__val}"
		eval "__${__tu}_static_vars=\"\${__${__tu}_static_vars} \
			${__var}\""
	done
}

EOF(){ :; }

: <<'EOF'
################################################################################
# Stack trace test
################################################################################
__tu=tu0
__tu0_static_vars=
__tu0_static_var_vals=
__tu0_static_fns=

a(){ __fn_start tu0 a; b; __fn_end; }
b(){ __fn_start tu0 b; c; __fn_end; }
c(){ __fn_start tu0 c; printf 'Stack trace:\n';
	printf '  * %s()\n' $(__stack_trace); __fn_end; }
a

__tu_end
EOF

#: <<'EOF'
################################################################################
# TU 0
################################################################################
__tu=tu0
__tu0_static_vars=
__tu0_static_var_vals=
__tu0_static_fns=

static v=1

foo()
{
	__fn_start tu0 foo

	echo "v (should be 1): $v"

	__fn_end
}

__tu_end

################################################################################
# TU 1
################################################################################
__tu=tu1
__tu1_static_vars=
__tu1_static_var_vals=
__tu1_static_fns=

bar()
{
	__fn_start tu1 bar

	echo "v (should not be 1): $v"
	foo
	echo "v (should not be 1): $v"

	__fn_end
}

__tu_end

bar
EOF

: <<'EOF'
################################################################################
# TU 0
################################################################################
__tu=tu0
__tu0_static_vars=
__tu0_static_var_vals=
__tu0_static_fns=

a()
{
	__fn_start tu0 a
	__local v=1
	echo "v (should be 1): $v"
	b
	echo "v (should be 1): $v"
	__fn_end
}

b()
{
	__fn_start tu0 b
	echo "v (should be empty): $v"
	__fn_end
}

__tu_end

a
EOF

: <<'EOF'
################################################################################
# TU 0
################################################################################
__tu=tu0
__tu0_static_vars=
__tu0_static_var_vals=
__tu0_static_fns=

a()
{
	__fn_start tu0 a
	static v=1
	__fn_end
}

__tu_end

a
EOF