From 125adb4bcd29df7b74d5e5aa34c527c2f68826c6 Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Wed, 24 Feb 2016 03:14:25 -0500
Subject: research: New stack management test script

---
diff --git a/research/research5.sh b/research/research5.sh
new file mode 100644
index 0000000..49d8548
--- /dev/null
+++ b/research/research5.sh
@@ -0,0 +1,308 @@
+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}"
+			for __fn in $(eval printf '%s' \
+					"\"\${__${__prev_tu}_static_fns}\""); do
+				unset -f "${__fn%:*}"
+			done
+	;; esac
+	case "${__fn_tu}" in
+		${__prev_tu});;
+		?*)
+			# Set static variables and function for the current TU.
+			eval "$(eval printf '%s' "\"$(eval printf '%s' \
+				"'\${__${__fn_tu}_static_var_vals}'")\"")"
+			for __fn in $(eval printf '%s' \
+					"\"\${__${__fn_tu}_static_fns}\""); 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
--
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