Support void' cast on functions called as tasks, bug1383.

Changes

@@ -8,7 +8,9 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ***   Support $fread.  [Leendert van Doorn]
 
-***   Add IGNOREDRETURN warning.
+***   Support void' cast on functions called as tasks, bug1383. [Al Grant]
+
+***   Add IGNOREDRETURN warning, bug1383.
 
 ****  Report PORTSHORT errors on concat constants, bug 1400. [Will Korteland]
 

bin/verilator

@@ -3583,7 +3583,12 @@ correctly.
 =item IGNOREDRETURN
 
 Warns that a non-void function is being called as a task, and hence the
-return value is being ignored. This warning is required by IEEE.
+return value is being ignored.
+
+This warning is required by IEEE. The portable way to suppress this warning
+(in SystemVerilog) is to use a void cast, e.g.
+
+    void'(function_being_called_as_task());
 
 Ignoring this warning will only suppress the lint check, it will simulate
 correctly.

src/verilog.y

@@ -2391,8 +2391,21 @@ statement_item<nodep>:		// IEEE: statement_item
 	//			// Below under expr
 	//
 	//			// IEEE: subroutine_call_statement
-	//UNSUP	yVOID yP_TICK '(' function_subroutine_callNoMethod ')' ';' { }
+	//			// IEEE says we then expect a function call
-	//UNSUP	yVOID yP_TICK '(' expr '.' function_subroutine_callNoMethod ')' ';' { }
+	//			// (function_subroutine_callNoMethod), but rest of
+	//			// the code expects an AstTask when used as a statement,
+	//			// so parse as if task
+	//			// Alternative would be shim with new AstVoidStmt.
+	|	yVOID yP_TICK '(' task_subroutine_callNoMethod ')' ';'
+							{ $$ = $4;
+							  FileLine* newfl = new FileLine($$->fileline());
+							  newfl->warnOff(V3ErrorCode::IGNOREDRETURN, true);
+							  $$->fileline(newfl); }
+	|	yVOID yP_TICK '(' expr '.' task_subroutine_callNoMethod ')' ';'
+							{ $$ = new AstDot($5, $4, $6);
+							  FileLine* newfl = new FileLine($6->fileline());
+							  newfl->warnOff(V3ErrorCode::IGNOREDRETURN, true);
+							  $6->fileline(newfl); }
 	//			// Expr included here to resolve our not knowing what is a method call
 	//			// Expr here must result in a subroutine_call
 	|	task_subroutine_callNoMethod ';'	{ $$ = $1; }
@@ -3965,7 +3978,7 @@ void V3ParseGrammar::argWrapList(AstNodeFTaskRef* nodep) {
 }
 
 AstNode* V3ParseGrammar::createSupplyExpr(FileLine* fileline, string name, int value) {
-    FileLine* newfl = new FileLine (fileline);
+    FileLine* newfl = new FileLine(fileline);
     newfl->warnOff(V3ErrorCode::WIDTH, true);
     AstNode* nodep = new AstConst(newfl, V3Number(newfl));
     // Adding a NOT is less work than figuring out how wide to make it

test_regress/t/t_func_void.v

@@ -26,8 +26,8 @@ module t (clk);
       // verilator lint_on IGNOREDRETURN
       if (side_effect != 33) $stop;
       //
-//      void'f1(30);
+      void'(f1(30));
-//      if (side_effect != 64) $stop;
+      if (side_effect != 64) $stop;
       //
       $write("*-* All Finished *-*\n");
       $finish;