Support $fflush without arguments, #1638.

Changes

@@ -7,6 +7,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 **    Add simplistic class support with many restrictions, see manual, #377.
 
+****  Support $fflush without arguments, #1638.
+
 
 * Verilator 4.032 2020-04-04
 

include/verilated.cpp

@@ -1181,6 +1181,10 @@ void VL_FCLOSE_I(IData fdi) VL_MT_SAFE {
     VerilatedImp::fdDelete(fdi);
 }
 
+void VL_FFLUSH_ALL() VL_MT_SAFE {
+    fflush(stdout);
+}
+
 void VL_SFORMAT_X(int obits, CData& destr, const char* formatp, ...) VL_MT_SAFE {
     static VL_THREAD_LOCAL std::string output;  // static only for speed
     output = "";

src/V3EmitC.cpp

@@ -557,7 +557,7 @@ public:
     }
     virtual void visit(AstFFlush* nodep) VL_OVERRIDE {
         if (!nodep->filep()) {
-            puts("fflush(stdout);\n");
+            puts("Verilated::flushCall();\n");
         } else {
             puts("if (");
             iterateAndNextNull(nodep->filep());

src/verilog.y

@@ -3232,7 +3232,7 @@ system_t_call<nodep>:		// IEEE: system_tf_call (as task)
 	|	yD_SYSTEM '(' expr ')'			{ $$ = new AstSystemT($1, $3); }
 	//
 	|	yD_FCLOSE '(' idClassSel ')'		{ $$ = new AstFClose($1, $3); }
-	|	yD_FFLUSH parenE			{ $$ = NULL; BBUNSUP($1, "Unsupported: $fflush of all handles does not map to C++."); }
+	|	yD_FFLUSH parenE			{ $$ = new AstFFlush($1, NULL); }
 	|	yD_FFLUSH '(' expr ')'			{ $$ = new AstFFlush($1, $3); }
 	|	yD_FINISH parenE			{ $$ = new AstFinish($1); }
 	|	yD_FINISH '(' expr ')'			{ $$ = new AstFinish($1); DEL($3); }

test_regress/t/t_sys_file_basic.v

@@ -61,6 +61,8 @@ module t;
       $fwriteb(file, "b: "); $fwriteb(file, i); $fwriteb(file, " "); $fdisplayb(file, i);
 
       $fflush(file);
+      $fflush();
+      $fflush;
 
       $fclose(file);
 `ifdef verilator