Add --Wfuture-, for improving forward compatibility.

Changes

@@ -18,6 +18,8 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ***  Add $random.
 
+***  Add --Wfuture-, for improving forward compatibility.
+
 **** Fix verilator_includer not being installed properly.  [Holger Waechtler]
 
 **** Fix IMPURE errors due to X-assignment temporary variables. [Steve Tong]

bin/verilator

@@ -224,6 +224,7 @@ descriptions in the next sections for more information.
     --underline-zero            Zero signals with leading _'s
     -v <filename>               Verilog library
     -Werror-<message>           Convert warning to error
+    -Wfuture-<message>          Disable unknown message warnings
     -Wno-<message>              Disable warning
     -x-assign <mode>            Initially assign Xs to this value
     -y <dir>                    Directory to search for modules
@@ -556,6 +557,14 @@ Convert the specified warning message into a error message.  This is
 generally to discourage users from violating important site-wide rules, for
 example C<-Werror-NOUNOPTFLAT>.
 
+=item -Wfuture-I<message>
+
+Suppress unknown Verilator comments or warning messages with the given
+message code.  This is used to allow code written with pragmas for a later
+version of Verilator to run under a older version; add -Wfuture- arguments
+for each message code or comment that the new version supports which the
+older version does not support.
+
 =item -Wno-I<message>
 
 Disable the specified warning message.

src/V3Options.cpp

@@ -95,6 +95,15 @@ void V3Options::addCppFile(const string& filename) {
 	m_cppFiles.insert(filename);
     }
 }
+void V3Options::addFuture(const string& flag) {
+    if (m_futures.find(flag) == m_futures.end()) {
+	m_futures.insert(flag);
+    }
+}
+bool V3Options::isFuture(const string& flag) const {
+    return m_futures.find(flag) != m_futures.end();
+}
+
 void V3Options::addLibraryFile(const string& filename) {
     if (m_libraryFiles.find(filename) == m_libraryFiles.end()) {
 	m_libraryFiles.insert(filename);
@@ -646,11 +655,18 @@ void V3Options::parseOptsList(FileLine* fl, int argc, char** argv) {
 		string msg = sw+strlen("-Werror-");
 		V3ErrorCode code (msg.c_str());
 		if (code == V3ErrorCode::ERROR) {
-		    fl->v3fatal("Unknown warning specified: "<<sw);
+		    if (!isFuture(msg)) {
+			fl->v3fatal("Unknown warning specified: "<<sw);
+		    }
 		} else {
 		    V3Error::pretendError(code, true);
 		}
 	    }
+	    else if ( !strncmp (sw, "-Wfuture-",strlen("-Wfuture-")) )	{
+		string msg = sw+strlen("-Wfuture-");
+		// Note it may not be a future option, but one that is currently implemented.
+		addFuture(msg);
+	    }
 	    else if ( !strcmp (sw, "-bin") && (i+1)<argc ) {
 		shift; m_bin = argv[i];
 	    }

src/V3Options.h

@@ -79,6 +79,7 @@ class V3Options {
     V3OptionsImp*	m_impp;		// Slow hidden options
 
     V3StringSet	m_cppFiles;	// argument: C++ files to link against
+    V3StringSet	m_futures;	// argument: -Wfuture- list
     V3StringSet	m_libraryFiles;	// argument: Verilog -v files
     V3StringList m_vFiles;	// argument: Verilog files to read
 
@@ -151,9 +152,10 @@ class V3Options {
   private:
     // METHODS
     void addArg(const string& incdir);
+    void addDefine(const string& defline);
+    void addFuture(const string& flag);
     void addIncDir(const string& incdir);
     void addLibExt(const string& libext);
-    void addDefine(const string& defline);
     void optimize(int level);
     void coverage(bool flag) { m_coverageLine = m_coverageUser = flag; }
     bool onoff(const char* sw, const char* arg, bool& flag);
@@ -219,11 +221,14 @@ class V3Options {
     string modPrefix() const { return m_modPrefix; }
     string topModule() const { return m_topModule; }
     string xAssign() const { return m_xAssign; }
+
     const V3StringSet& cppFiles() const { return m_cppFiles; }
     const V3StringSet& libraryFiles() const { return m_libraryFiles; }
     const V3StringList& vFiles() const { return m_vFiles; }
     const V3LangCode& language() const { return m_language; }
 
+    bool isFuture(const string& flag) const;
+
     // ACCESSORS (optimization options)
     bool oAcycSimp() const { return m_oAcycSimp; }
     bool oCase() const { return m_oCase; }

src/V3Read.cpp

@@ -181,6 +181,9 @@ void V3Read::lexFile(const string& modname) {
 bool V3Read::optPsl() {
     return v3Global.opt.psl();
 }
+bool V3Read::optFuture(const string& flag) {
+    return v3Global.opt.isFuture(flag);
+}
 
 //======================================================================
 // Lex internal functions

src/V3Read.h

@@ -56,6 +56,7 @@ protected:
     friend class V3PreShellImp;
     int yylexThis();
     static bool optPsl();
+    static bool optFuture(const string& flag);
     static void ppline (const char* text);
     static void incLineno() { s_readp->fileline()->incLineno(); }
     static void verilatorCmtLint(const char* text, bool on);

src/verilog.l

@@ -54,7 +54,9 @@ void V3Read::verilatorCmtLint(const char* textp, bool warnOff) {
     string::size_type pos;
     if ((pos=msg.find("*")) != string::npos) { msg.erase(pos); }
     if (!(V3Read::fileline()->warnOff(msg, warnOff))) {
-	yyerrorf("Unknown verilator lint message code: %s, in %s",msg.c_str(), textp);
+	if (!V3Read::optFuture(msg)) {
+	    yyerrorf("Unknown verilator lint message code: %s, in %s",msg.c_str(), textp);
+	}
     }
 }
 
@@ -71,7 +73,20 @@ void V3Read::verilatorCmtLintRestore() {
 }
 
 void V3Read::verilatorCmtBad(const char* textp) {
-    yyerrorf("Unknown verilator comment: %s",textp);
+    string cmtparse = textp;
+    if (cmtparse.substr(0,strlen("/*verilator")) == "/*verilator") {
+	cmtparse.replace(0,strlen("/*verilator"), "");
+    }
+    while (isspace(cmtparse[0])) {
+	cmtparse.replace(0,1, "");
+    }
+    string cmtname;
+    for (int i=0; isalnum(cmtparse[i]); i++) {
+	cmtname += cmtparse[i];
+    }
+    if (!V3Read::optFuture(cmtname)) {
+	yyerrorf("Unknown verilator comment: %s",textp);
+    }
 }
 
 // See V3Read.cpp

test_regress/t/t_flag_future.pl

@@ -0,0 +1,18 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("./driver.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2008 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 (
+	 verilator_flags2 => [qw(-Wfuture-FUTURE1 -Wfuture-FUTURE2)],
+	 );
+
+execute (
+	 check_finished=>1,
+	 );
+
+ok(1);
+1;

test_regress/t/t_flag_future.v

@@ -0,0 +1,11 @@
+// DESCRIPTION: Verilator: Verilog Test module
+
+module t;
+   initial begin
+      // verilator lint_off FUTURE1
+      $write("*-* All Finished *-*\n");
+      $finish;
+      // verilator FUTURE2
+      // verilator FUTURE2 blah blah
+   end
+endmodule