Fix preprocessor

Refactorize preprocessor and fixes nested if else conditions.

Author: boriel

tests/functional/prepro95.bi

@@ -0,0 +1,13 @@
+
+#ifdef MACRO
+#  define ANOTHER
+
+#  ifdef ANOTHER
+#    error This should never happen
+#  else
+#    error This should never happen
+#  endif
+#else
+ OK
+#endif
+

tests/functional/prepro95.out

@@ -0,0 +1,4 @@
+#line 1 "prepro95.bi"
+#line 11 "prepro95.bi"
+ OK
+#line 13 "prepro95.bi"

zxbpp/zxbpp.py

@@ -15,6 +15,7 @@
 import os
 import re
 import argparse
+from typing import NamedTuple, List
 
 from .zxbpplex import tokens  # noqa
 from . import zxbpplex, zxbasmpplex
@@ -45,10 +46,16 @@
 INCLUDEPATH = ('library', 'library-asm')
 
 # Enabled to FALSE if IFDEF failed
-ENABLED = True
+ENABLED: bool = True
+
+
+class IfDef(NamedTuple):
+    enabled: bool
+    line: int
+
 
 # IFDEFS array
-IFDEFS = []  # Push (Line, state here)
+IFDEFS: List[IfDef] = []  # Push (Line, state here)
 
 
 precedence = (
@@ -484,36 +491,37 @@ def p_ifdef(p):
 
     if ENABLED:
         p[0] = [p[2]] + p[3]
-        p[0] += ['#line %i "%s"' % (p.lineno(4) + 1, CURRENT_FILE[-1])]
     else:
-        p[0] = ['#line %i "%s"' % (p.lineno(4) + 1, CURRENT_FILE[-1])]
+        p[0] = []
 
-    ENABLED = IFDEFS[-1][0]
-    IFDEFS.pop()
+    p[0] += ['#line %i "%s"' % (p.lineno(4) + 1, CURRENT_FILE[-1])]
+    ENABLED = IFDEFS.pop().enabled
 
 
 def p_ifdef_else(p):
     """ ifdef : ifdefelsea ifdefelseb ENDIF
     """
     global ENABLED
 
-    p[0] = p[1] + p[2]
+    ENABLED = IFDEFS.pop().enabled
+    if ENABLED:
+        p[0] = p[1] + p[2]
+    else:
+        p[0] = []
+
     p[0] += ['#line %i "%s"' % (p.lineno(3) + 1, CURRENT_FILE[-1])]
-    ENABLED = IFDEFS[-1][0]
-    IFDEFS.pop()
 
 
 def p_ifdef_else_a(p):
     """ ifdefelsea : if_header NEWLINE program
     """
     global ENABLED
 
-    if ENABLED:
-        p[0] = [p[2]] + p[3]
-    else:
-        p[0] = []
-
-    ENABLED = not ENABLED
+    p[0] = []
+    if IFDEFS[-1].enabled:
+        if p[1]:
+            p[0] = [p[2]] + p[3]
+        ENABLED = not p[1]
 
 
 def p_ifdef_else_b(p):
@@ -533,29 +541,36 @@ def p_if_header(p):
     """
     global ENABLED
 
-    IFDEFS.append((ENABLED, p.lineno(2)))
-    ENABLED = ID_TABLE.defined(p[2])
+    IFDEFS.append(IfDef(ENABLED, p.lineno(2)))
+    if ENABLED:
+        ENABLED = ID_TABLE.defined(p[2])
+
+    p[0] = ENABLED
 
 
 def p_ifn_header(p):
     """ if_header : IFNDEF ID
     """
     global ENABLED
 
-    IFDEFS.append((ENABLED, p.lineno(2)))
+    IFDEFS.append(IfDef(ENABLED, p.lineno(2)))
     if ENABLED:
         ENABLED = not ID_TABLE.defined(p[2])
 
+    p[0] = ENABLED
+
 
 def p_if_expr_header(p):
     """ if_header : IF expr
     """
     global ENABLED
 
-    IFDEFS.append((ENABLED, p.lineno(1)))
+    IFDEFS.append(IfDef(ENABLED, p.lineno(2)))
     if ENABLED:
         ENABLED = bool(int(p[2])) if p[2].isdigit() else ID_TABLE.defined(p[2])
 
+    p[0] = ENABLED
+
 
 def p_expr(p):
     """ expr : macrocall