From d2d38edf06ff9a0307f49a7bd19a617d27705ecb Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Tue, 6 May 2008 00:50:47 +0000
Subject: [PATCH] Fix preprocessor `else after series of `elsif.  [Mark Nodine]

git-svn-id: file://localhost/svn/verilator/trunk/verilator@1047 77ca24e4-aefa-0310-84f0-b9a241c72d87
---
 Changes                           |  2 ++
 src/V3PreProc.cpp                 | 43 +++++++++++++++++++++---------
 test_regress/t/t_preproc_ifdef.pl | 18 +++++++++++++
 test_regress/t/t_preproc_ifdef.v  | 44 +++++++++++++++++++++++++++++++
 4 files changed, 94 insertions(+), 13 deletions(-)
 create mode 100755 test_regress/t/t_preproc_ifdef.pl
 create mode 100644 test_regress/t/t_preproc_ifdef.v

diff --git a/Changes b/Changes
index df3378fc0..ec2c747e6 100644
--- a/Changes
+++ b/Changes
@@ -7,6 +7,8 @@ indicates the contributor was also the author of the fix; Thanks!
 
 **** Fix compiler warnings under GCC 4.2.1.
 
+**** Fix preprocessor `else after series of `elsif.  [Mark Nodine]
+
 * Verilator 3.662 2008/04/25
 
 ***  Add Verilog 2005 $clog2() function.
diff --git a/src/V3PreProc.cpp b/src/V3PreProc.cpp
index b7eb22fcb..810e27d59 100644
--- a/src/V3PreProc.cpp
+++ b/src/V3PreProc.cpp
@@ -83,6 +83,21 @@ public:
     ~V3DefineRef() {}
 };
 
+//*************************************************************************
+/// Data for parsing on/off
+
+class VPreIfEntry {
+    // One for each pending ifdef/ifndef
+    bool	m_on;		// Current parse for this ifdef level is "on"
+    bool	m_everOn;	// Some if term in elsif tree has been on
+public:
+    bool on() const { return m_on; }
+    bool everOn() const { return m_everOn; }
+    VPreIfEntry(bool on, bool everOn)
+	: m_on(on), m_everOn(everOn || on) {}  // Note everOn includes new state
+    ~VPreIfEntry() {}
+};
+
 //*************************************************************************
 // Data for a preprocessor instantiation.
 
@@ -111,7 +126,7 @@ struct V3PreProcImp : public V3PreProc {
 
     // For defines
     stack<V3DefineRef> m_defRefs; // Pending definine substitution
-    stack<bool> m_ifdefStack;	// Stack of true/false emitting evaluations
+    stack<VPreIfEntry> m_ifdefStack;	///< Stack of true/false emitting evaluations
     unsigned	m_defDepth;	// How many `defines deep
 
     // Defines list
@@ -655,7 +670,7 @@ int V3PreProcImp::getToken() {
 		    bool enable = defExists(m_lastSym);
 		    UINFO(4,"Ifdef "<<m_lastSym<<(enable?" ON":" OFF")<<endl);
 		    if (m_stateFor==VP_IFNDEF) enable = !enable;
-		    m_ifdefStack.push(enable);
+		    m_ifdefStack.push(VPreIfEntry(enable,false));
 		    if (!enable) parsingOff();
 		}
 		else if (m_stateFor==VP_ELSIF) {
@@ -663,12 +678,12 @@ int V3PreProcImp::getToken() {
 			fileline()->v3error("`elsif with no matching `if\n");
 		    } else {
 			// Handle `else portion
-			bool lastEnable = m_ifdefStack.top(); m_ifdefStack.pop();
-			if (!lastEnable) parsingOn();
+			VPreIfEntry lastIf = m_ifdefStack.top(); m_ifdefStack.pop();
+			if (!lastIf.on()) parsingOn();
 			// Handle `if portion
-			bool enable = !lastEnable && defExists(m_lastSym);
+			bool enable = !lastIf.everOn() && defExists(m_lastSym);
 			UINFO(4,"Elsif "<<m_lastSym<<(enable?" ON":" OFF")<<endl);
-			m_ifdefStack.push(enable);
+			m_ifdefStack.push(VPreIfEntry(enable, lastIf.everOn()));
 			if (!enable) parsingOff();
 		    }
 		}
@@ -856,21 +871,23 @@ int V3PreProcImp::getToken() {
 	    if (m_ifdefStack.empty()) {
 		fileline()->v3error("`else with no matching `if\n");
 	    } else {
-		bool lastEnable = m_ifdefStack.top(); m_ifdefStack.pop();
-		bool enable = !lastEnable;
+		VPreIfEntry lastIf = m_ifdefStack.top(); m_ifdefStack.pop();
+		bool enable = !lastIf.everOn();
 		UINFO(4,"Else "<<(enable?" ON":" OFF")<<endl);
-		m_ifdefStack.push(enable);
-		if (!lastEnable) parsingOn();
+		m_ifdefStack.push(VPreIfEntry(enable, lastIf.everOn()));
+		if (!lastIf.on()) parsingOn();
 		if (!enable) parsingOff();
 	    }
 	    goto next_tok;
 	case VP_ENDIF:
+	    UINFO(4,"Endif "<<endl);
 	    if (m_ifdefStack.empty()) {
 		fileline()->v3error("`endif with no matching `if\n");
 	    } else {
-		bool lastEnable = m_ifdefStack.top(); m_ifdefStack.pop();
-		UINFO(4,"Endif "<<endl);
-		if (!lastEnable) parsingOn();
+		VPreIfEntry lastIf = m_ifdefStack.top(); m_ifdefStack.pop();
+		if (!lastIf.on()) parsingOn();
+		// parsingOn() really only enables parsing if
+		// all ifdef's above this want it on
 	    }
 	    goto next_tok;
 
diff --git a/test_regress/t/t_preproc_ifdef.pl b/test_regress/t/t_preproc_ifdef.pl
new file mode 100755
index 000000000..7bfdbe852
--- /dev/null
+++ b/test_regress/t/t_preproc_ifdef.pl
@@ -0,0 +1,18 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("./driver.pl", @ARGV, $0); die; }
+# $Id$
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# General Public License or the Perl Artistic License.
+
+compile (
+	 );
+
+execute (
+	 check_finished=>1,
+     );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_preproc_ifdef.v b/test_regress/t/t_preproc_ifdef.v
new file mode 100644
index 000000000..61cfad07d
--- /dev/null
+++ b/test_regress/t/t_preproc_ifdef.v
@@ -0,0 +1,44 @@
+// $Id$
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2007 by Wilson Snyder.
+
+module t (/*AUTOARG*/);
+   integer num;
+   initial begin
+      num = 0;
+
+`define EMPTY_TRUE
+`ifndef EMPTY_TRUE
+  `error "Empty is still true"
+`endif
+
+`define A
+`ifdef A	$display("1A"); num = num + 1;
+ `ifdef C	$stop;
+ `elsif A	$display("2A"); num = num + 1;
+  `ifdef C	$stop;
+  `elsif B	$stop;
+  `else		$display("3A"); num = num + 1;
+  `endif
+ `else		$stop;
+ `endif
+ `elsif B	$stop;
+  `ifdef A	$stop;
+  `elsif A	$stop;
+  `else
+  `endif
+`elsif C	$stop;
+`else		$stop;
+`endif
+      if (num == 3) begin
+	 $write("*-* All Finished *-*\n");
+	 $finish;
+      end
+      else begin
+	 $write("%%Error: Bad count: %d\n", num);
+	 $stop;
+      end
+   end
+endmodule