Fix missing class forward declarations (#4151)

src/V3CUse.cpp

@@ -45,12 +45,16 @@ class CUseVisitor final : public VNVisitor {
     const VNUser1InUse m_inuser1;
 
     // MEMBERS
-    bool m_impOnly = false;  // In details needed only for implementation
     AstNodeModule* const m_modp;  // Current module
     std::set<std::pair<VUseType, std::string>> m_didUse;  // What we already used
+    bool m_dtypesImplOnly = false;
 
     // METHODS
     void addNewUse(AstNode* nodep, VUseType useType, const string& name) {
+        if (m_dtypesImplOnly
+            && (useType == VUseType::INT_INCLUDE || useType == VUseType::INT_FWD_CLASS))
+            return;
+
         if (m_didUse.emplace(useType, name).second) {
             AstCUse* const newp = new AstCUse{nodep->fileline(), useType, name};
             m_modp->addStmtsp(newp);
@@ -61,12 +65,29 @@ class CUseVisitor final : public VNVisitor {
     // VISITORS
     void visit(AstClassRefDType* nodep) override {
         if (nodep->user1SetOnce()) return;  // Process once
-        if (!m_impOnly) addNewUse(nodep, VUseType::INT_FWD_CLASS, nodep->classp()->name());
-        // Need to include extends() when we implement, but no need for pointers to know
-        VL_RESTORER(m_impOnly);
+        addNewUse(nodep, VUseType::INT_FWD_CLASS, nodep->classp()->name());
+    }
+    void visit(AstCFunc* nodep) override {
+        if (nodep->user1SetOnce()) return;  // Process once
+        iterateAndNextNull(nodep->argsp());
+
         {
-            m_impOnly = true;
-            iterateChildren(nodep->classp());  // This also gets all extend classes
+            VL_RESTORER(m_dtypesImplOnly);
+            m_dtypesImplOnly = true;
+
+            iterateAndNextNull(nodep->initsp());
+            iterateAndNextNull(nodep->stmtsp());
+            iterateAndNextNull(nodep->finalsp());
+        }
+    }
+    void visit(AstCReturn* nodep) override {
+        if (nodep->user1SetOnce()) return;  // Process once
+        if (m_dtypesImplOnly) {
+            for (AstNode* exprp = nodep->op1p(); exprp; exprp = exprp->nextp()) {
+                if (exprp->dtypep()) iterate(exprp->dtypep());
+            }
+        } else {
+            iterateChildren(nodep);
         }
     }
     void visit(AstNodeDType* nodep) override {
@@ -79,6 +100,8 @@ class CUseVisitor final : public VNVisitor {
         if (stypep && stypep->classOrPackagep()) {
             addNewUse(nodep, VUseType::INT_INCLUDE, stypep->classOrPackagep()->name());
             iterateChildren(stypep);
+        } else if (AstClassRefDType* const classp = VN_CAST(nodep->skipRefp(), ClassRefDType)) {
+            addNewUse(nodep, VUseType::INT_FWD_CLASS, classp->name());
         }
     }
     void visit(AstNode* nodep) override {

src/V3EmitCBase.cpp

@@ -224,21 +224,12 @@ void EmitCBaseVisitorConst::emitVarDecl(const AstVar* nodep, bool asRef) {
 }
 
 void EmitCBaseVisitorConst::emitModCUse(const AstNodeModule* modp, VUseType useType) {
-    string nl;
-    for (AstNode* itemp = modp->stmtsp(); itemp; itemp = itemp->nextp()) {
-        if (AstCUse* const usep = VN_CAST(itemp, CUse)) {
-            if (usep->useType() == useType) {
-                if (usep->useType().isInclude()) {
-                    puts("#include \"" + prefixNameProtect(usep) + ".h\"\n");
-                }
-                if (usep->useType().isFwdClass()) {
-                    puts("class " + prefixNameProtect(usep) + ";\n");
-                }
-                nl = "\n";
-            }
-        }
-    }
-    puts(nl);
+    bool nl = false;
+    forModCUse(modp, useType, [&](string entry) {
+        puts(entry);
+        nl = true;
+    });
+    if (nl) puts("\n");
 }
 
 void EmitCBaseVisitorConst::emitTextSection(const AstNodeModule* modp, VNType type) {

src/V3EmitCBase.h

@@ -113,6 +113,21 @@ public:
     void emitCFuncHeader(const AstCFunc* funcp, const AstNodeModule* modp, bool withScope);
     void emitCFuncDecl(const AstCFunc* funcp, const AstNodeModule* modp, bool cLinkage = false);
     void emitVarDecl(const AstVar* nodep, bool asRef = false);
+    template <typename F>
+    static void forModCUse(const AstNodeModule* modp, VUseType useType, F action) {
+        for (AstNode* itemp = modp->stmtsp(); itemp; itemp = itemp->nextp()) {
+            if (AstCUse* const usep = VN_CAST(itemp, CUse)) {
+                if (usep->useType() == useType) {
+                    if (usep->useType().isInclude()) {
+                        action("#include \"" + prefixNameProtect(usep) + ".h\"\n");
+                    }
+                    if (usep->useType().isFwdClass()) {
+                        action("class " + prefixNameProtect(usep) + ";\n");
+                    }
+                }
+            }
+        }
+    }
     void emitModCUse(const AstNodeModule* modp, VUseType useType);
     void emitTextSection(const AstNodeModule* modp, VNType type);
 

src/V3EmitCHeaders.cpp

@@ -22,6 +22,7 @@
 #include "V3Global.h"
 
 #include <algorithm>
+#include <set>
 #include <vector>
 
 VL_DEFINE_DEBUG_FUNCTIONS;
@@ -287,11 +288,9 @@ class EmitCHeader final : public EmitCConstInit {
                      + ".h\"\n");
             }
         }
-        emitModCUse(modp, VUseType::INT_INCLUDE);
 
         // Forward declarations required by this AstNodeModule
         puts("\nclass " + symClassName() + ";\n");
-        emitModCUse(modp, VUseType::INT_FWD_CLASS);
 
         // From `systemc_header
         emitTextSection(modp, VNType::atScHdr);
@@ -361,6 +360,19 @@ class EmitCHeader final : public EmitCConstInit {
         if (v3Global.opt.coverage()) puts("#include \"verilated_cov.h\"\n");
         if (v3Global.usesTiming()) puts("#include \"verilated_timing.h\"\n");
 
+        std::set<string> cuse_set;
+        auto add_to_cuse_set = [&](string s) { cuse_set.insert(s); };
+
+        forModCUse(modp, VUseType::INT_INCLUDE, add_to_cuse_set);
+        forModCUse(modp, VUseType::INT_FWD_CLASS, add_to_cuse_set);
+        if (const AstClassPackage* const packagep = VN_CAST(modp, ClassPackage)) {
+            forModCUse(packagep->classp(), VUseType::INT_INCLUDE, add_to_cuse_set);
+            forModCUse(packagep->classp(), VUseType::INT_FWD_CLASS, add_to_cuse_set);
+        }
+
+        for (const string& s : cuse_set) puts(s);
+        puts("\n");
+
         emitAll(modp);
 
         if (const AstClassPackage* const packagep = VN_CAST(modp, ClassPackage)) {

test_regress/t/t_cuse_forward.pl

@@ -0,0 +1,17 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(vlt => 1);
+
+compile(
+       );
+
+ok(1);
+1;

test_regress/t/t_cuse_forward.v

@@ -0,0 +1,39 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Antmicro Ltd.
+// SPDX-License-Identifier: CC0-1.0
+
+class Baz;
+endclass
+
+class Bar#(type T) extends T;
+endclass
+
+class Foo;
+  typedef struct {
+    int field;
+  } Zee;
+
+  task t1();
+    // Refer to Baz CLASSREFDTYPE node in implementation (via CLASSEXTENDS)
+    Bar#(Baz) b = new;
+  endtask
+  // Refer to the very same Baz CLASSREFDTYPE node again, this time within interface
+  task t2(Bar#(Baz)::T b);
+  endtask
+endclass
+
+class Moo;
+  // Use Foo::Zee to cause inclusion of Foo's header file
+  Foo::Zee z;
+endclass
+
+module t();
+  initial begin
+    // Use Moo in top module to add Moo to root, causing inclusion of Foo header into
+    // root header.
+    Moo moo;
+    moo = new;
+  end
+endmodule