macroprocessor: add @#ifdef

macro/MacroBison.yy

@@ -79,7 +79,7 @@ class MacroDriver;
 
 %}
 
-%token DEFINE LINE FOR IN IF ELSE ENDIF ECHO_DIR ERROR
+%token DEFINE LINE FOR IN IF ELSE ENDIF ECHO_DIR ERROR IFDEF
 %token LPAREN RPAREN LBRACKET RBRACKET EQUAL EOL
 
 %token <int_val> INTEGER
@@ -117,6 +117,8 @@ statement : expr
             { TYPERR_CATCH(driver.init_loop(*$2, $4), @$); delete $2; }
           | IF expr
             { TYPERR_CATCH(driver.begin_if($2), @$); }
+          | IFDEF NAME
+            { TYPERR_CATCH(driver.begin_ifdef(*$2), @$); delete $2; }
           | ECHO_DIR expr
             { TYPERR_CATCH(driver.echo(@$, $2), @$); }
           | ERROR expr

macro/MacroDriver.cc

@@ -164,6 +164,24 @@ MacroDriver::begin_if(const MacroValue *value) throw (MacroValue::TypeError)
   last_if = (bool) ival->value;
 }
 
+void
+MacroDriver::begin_ifdef(const string &name)
+{
+  try
+    {
+      get_variable(name);
+      const MacroValue *one = new IntMV(*this, 1);
+      begin_if(one);
+      delete one;
+    }
+  catch (UnknownVariable &)
+    {
+      const MacroValue *zero = new IntMV(*this, 0);
+      begin_if(zero);
+      delete zero;
+    }
+}
+
 void
 MacroDriver::echo(const Macro::parser::location_type &l, const MacroValue *value) const throw (MacroValue::TypeError)
 {

macro/MacroDriver.hh

@@ -208,6 +208,9 @@ public:
   //! Begins an @#if statement
   void begin_if(const MacroValue *value) throw (MacroValue::TypeError);
 
+  //! Begins an @#ifdef statement
+  void begin_ifdef(const string &name);
+
   //! Executes @#echo directive
   void echo(const Macro::parser::location_type &l, const MacroValue *value) const throw (MacroValue::TypeError);
 

macro/MacroFlex.ll

@@ -164,6 +164,8 @@ CONT \\\\
 <STMT>for                   { reading_for_statement = true; return token::FOR; }
 <STMT>endfor                { driver.error(*yylloc, "@#endfor is not matched by a @#for statement"); }
 
+<STMT>ifdef                 { reading_if_statement = true; return token::IFDEF; }
+
 <STMT>if                    { reading_if_statement = true; return token::IF; }
 <STMT>else                  { driver.error(*yylloc, "@#else is not matched by an @#if statement"); }
 <STMT>endif                 { driver.error(*yylloc, "@#endif is not matched by an @#if statement"); }