Support $ferror, #1638.

Changes

@@ -7,7 +7,7 @@ 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.
+****  Support $ferror, and $fflush without arguments, #1638.
 
 
 * Verilator 4.032 2020-04-04

bin/verilator

@@ -3867,7 +3867,8 @@ $dumplimit/$dumpportlimit are currently ignored.
 
 The rarely used optional parameter to $finish and $stop is ignored.
 
-=item $fopen, $fclose, $fdisplay, $feof, $fflush, $fgetc, $fgets, $fscanf, $fwrite
+=item $fopen, $fclose, $fdisplay, $ferror, $feof, $fflush, $fgetc, $fgets,
+$fscanf, $fwrite
 
 File descriptors passed to the file PLI calls must be file descriptors, not
 MCDs, which includes the mode parameter to $fopen being mandatory.

include/verilated.cpp

@@ -1148,6 +1148,13 @@ IData VL_FGETS_IXI(int obits, void* destp, IData fpi) VL_MT_SAFE {
     return got;
 }
 
+IData VL_FERROR_IN(IData, std::string& outputr) VL_MT_SAFE {
+    // We ignore lhs/fpi - IEEE says "most recent error" so probably good enough
+    IData ret = errno;
+    outputr = std::string(::strerror(ret));
+    return ret;
+}
+
 IData VL_FOPEN_NI(const std::string& filename, IData mode) VL_MT_SAFE {
     // While threadsafe, each thread can only access different file handles
     char modez[5];

include/verilated_heavy.h

@@ -424,6 +424,7 @@ inline IData VL_LEN_IN(const std::string& ld) { return ld.length(); }
 extern std::string VL_TOLOWER_NN(const std::string& ld);
 extern std::string VL_TOUPPER_NN(const std::string& ld);
 
+extern IData VL_FERROR_IN(IData fpi, std::string& outputr) VL_MT_SAFE;
 extern IData VL_FOPEN_NI(const std::string& filename, IData mode) VL_MT_SAFE;
 extern void VL_READMEM_N(bool hex, int bits, QData depth, int array_lsb,
                          const std::string& filename, void* memp, QData start,

src/V3AstNodes.h

@@ -4912,6 +4912,30 @@ public:
     AstNode* filep() const { return lhsp(); }
 };
 
+class AstFError : public AstNodeMath {
+public:
+    AstFError(FileLine* fl, AstNode* filep, AstNode* strp)
+        : ASTGEN_SUPER(fl) {
+        setOp1p(filep);
+        setOp2p(strp);
+    }
+    ASTNODE_NODE_FUNCS(FError)
+    virtual void numberOperate(V3Number& out, const V3Number& lhs) { V3ERROR_NA; }
+    virtual string emitVerilog() { return "%f$ferror(%l, %r)"; }
+    virtual string emitC() { V3ERROR_NA_RETURN(""); }
+    virtual bool cleanOut() const { return true; }
+    virtual bool cleanLhs() const { return true; }
+    virtual bool sizeMattersLhs() const { return false; }
+    virtual int instrCount() const { return widthInstrs() * 64; }
+    virtual bool isPure() const { return false; }  // SPECIAL: $display has 'visual' ordering
+    void filep(AstNode* nodep) { setOp1p(nodep); }
+    AstNode* filep() const { return op1p(); }
+    void strp(AstNode* nodep) { setOp2p(nodep); }
+    AstNode* strp() const { return op2p(); }
+    virtual V3Hash sameHash() const { return V3Hash(); }
+    virtual bool same(const AstNode* samep) const { return true; }
+};
+
 class AstFGetC : public AstNodeUniop {
 public:
     AstFGetC(FileLine* fl, AstNode* lhsp)

src/V3EmitC.cpp

@@ -482,6 +482,13 @@ public:
         putsQuoted(nodep->text());
         puts(")");
     }
+    virtual void visit(AstFError* nodep) VL_OVERRIDE {
+        puts("VL_FERROR_IN(");
+        iterateAndNextNull(nodep->filep());
+        putbs(", ");
+        iterateAndNextNull(nodep->strp());
+        puts(")");
+    }
     virtual void visit(AstFGetS* nodep) VL_OVERRIDE {
         checkMaxWords(nodep);
         emitOpName(nodep, nodep->emitC(), nodep->lhsp(), nodep->rhsp(), NULL);

src/V3LinkLValue.cpp

@@ -102,6 +102,16 @@ private:
         }
         m_setRefLvalue = last_setRefLvalue;
     }
+    virtual void visit(AstFError* nodep) VL_OVERRIDE {
+        bool last_setRefLvalue = m_setRefLvalue;
+        {
+            m_setRefLvalue = true;
+            iterateAndNextNull(nodep->filep());
+            iterateAndNextNull(nodep->strp());
+            m_setRefLvalue = false;
+        }
+        m_setRefLvalue = last_setRefLvalue;
+    }
     virtual void visit(AstFFlush* nodep) VL_OVERRIDE {
         bool last_setRefLvalue = m_setRefLvalue;
         {

src/V3LinkResolve.cpp

@@ -378,6 +378,10 @@ private:
         iterateChildren(nodep);
         expectDescriptor(nodep, VN_CAST(nodep->filep(), NodeVarRef));
     }
+    virtual void visit(AstFError* nodep) VL_OVERRIDE {
+        iterateChildren(nodep);
+        expectDescriptor(nodep, VN_CAST(nodep->filep(), NodeVarRef));
+    }
     virtual void visit(AstFEof* nodep) VL_OVERRIDE {
         iterateChildren(nodep);
         expectDescriptor(nodep, VN_CAST(nodep->filep(), NodeVarRef));

src/V3Width.cpp

@@ -3088,6 +3088,14 @@ private:
         assertAtStatement(nodep);
         iterateCheckFileDesc(nodep, nodep->filep(), BOTH);
     }
+    virtual void visit(AstFError* nodep) VL_OVERRIDE {
+        if (m_vup->prelim()) {
+            iterateCheckFileDesc(nodep, nodep->filep(), BOTH);
+            // We only support string types, not packed array
+            iterateCheckString(nodep, "$ferror string result", nodep->strp(), BOTH);
+            nodep->dtypeSetLogicUnsized(32, 1, AstNumeric::SIGNED);  // Spec says integer return
+        }
+    }
     virtual void visit(AstFEof* nodep) VL_OVERRIDE {
         if (m_vup->prelim()) {
             iterateCheckFileDesc(nodep, nodep->filep(), BOTH);

src/verilog.l

@@ -217,6 +217,7 @@ vnum    {vnum1}|{vnum2}|{vnum3}|{vnum4}|{vnum5}
   "$fdisplayh"          { FL; return yD_FDISPLAYH; }
   "$fdisplayo"          { FL; return yD_FDISPLAYO; }
   "$feof"               { FL; return yD_FEOF; }
+  "$ferror"             { FL; return yD_FERROR; }
   "$fflush"             { FL; return yD_FFLUSH; }
   "$fgetc"              { FL; return yD_FGETC; }
   "$fgets"              { FL; return yD_FGETS; }

src/verilog.y

@@ -570,6 +570,7 @@ class AstSenTree;
 %token<fl>		yD_FDISPLAYH	"$fdisplayh"
 %token<fl>		yD_FDISPLAYO	"$fdisplayo"
 %token<fl>		yD_FEOF		"$feof"
+%token<fl>		yD_FERROR	"$ferror"
 %token<fl>		yD_FFLUSH	"$fflush"
 %token<fl>		yD_FGETC	"$fgetc"
 %token<fl>		yD_FGETS	"$fgets"
@@ -3331,6 +3332,7 @@ system_f_call_or_t<nodep>:	// IEEE: part of system_tf_call (can be task or func)
 	|	yD_DIMENSIONS '(' exprOrDataType ')'	{ $$ = new AstAttrOf($1,AstAttrType::DIM_DIMENSIONS,$3); }
 	|	yD_EXP '(' expr ')'			{ $$ = new AstExpD($1,$3); }
 	|	yD_FEOF '(' expr ')'			{ $$ = new AstFEof($1,$3); }
+	|	yD_FERROR '(' idClassSel ',' idClassSel ')'	{ $$ = new AstFError($1, $3, $5); }
 	|	yD_FGETC '(' expr ')'			{ $$ = new AstFGetC($1,$3); }
 	|	yD_FGETS '(' idClassSel ',' expr ')'	{ $$ = new AstFGetS($1,$3,$5); }
 	|	yD_FREAD '(' idClassSel ',' expr ')'	{ $$ = new AstFRead($1,$3,$5,NULL,NULL); }

test_regress/t/t_sys_file_basic.v

@@ -9,6 +9,8 @@
 `define STRINGIFY(x) `"x`"
 `define ratio_error(a,b) (((a)>(b) ? ((a)-(b)) : ((b)-(a))) /(a))
 `define checkr(gotv,expv) do if (`ratio_error((gotv),(expv))>0.0001) begin $write("%%Error: %s:%0d:  got=%g exp=%g\n", `__FILE__,`__LINE__, (gotv), (expv)); $stop; end while(0);
+`define checkh(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); $stop; end while(0);
+`define checks(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='%s' exp='%s'\n", `__FILE__,`__LINE__, (gotv), (expv)); $stop; end while(0);
 
 module t;
    integer file;
@@ -75,6 +77,11 @@ module t;
 	 // The "r" is required so we get a FD not a MFD
          file = $fopen("DOES_NOT_EXIST","r");
 	 if (|file) $stop;	// Should not exist, IE must return 0
+	 // Check error function
+	 s = "";
+	 i = $ferror(file, s);
+	 `checkh(i, 2);
+	 `checks(s, "No such file or directory");
       end
 
       begin