diff --git a/src/.dscanner.ini b/src/.dscanner.ini
index d6e14cdc02e9..45dbfd836814 100644
--- a/src/.dscanner.ini
+++ b/src/.dscanner.ini
@@ -115,5 +115,5 @@ redundant_storage_classes="enabled"
 redundant_storage_classes="-dmd.id,-dmd.toir,-dmd.tokens"
 trust_too_much="-dmd.root.longdouble"
 builtin_property_names_check="-dmd.backend.obj,-dmd.backend.code,-dmd.backend.cc"
-object_const_check="-dmd.dtemplate,-dmd.backend.outbuf"
+object_const_check="-dmd.dtemplate,-dmd.backend.outbuf,-dmd.root.rootobject"
 final_attribute_check="-dmd.statement" ; https://github.com/dlang/dmd/pull/856
diff --git a/src/dmd/dmodule.d b/src/dmd/dmodule.d
index 52c4c2c72e0e..aa7a6b422041 100644
--- a/src/dmd/dmodule.d
+++ b/src/dmd/dmodule.d
@@ -38,6 +38,7 @@ import dmd.root.port;
 import dmd.semantic2;
 import dmd.semantic3;
 import dmd.target;
+import dmd.utils;
 import dmd.visitor;
 
 version(Windows) {
@@ -1337,19 +1338,24 @@ struct ModuleDeclaration
         this.isdeprecated = isdeprecated;
     }
 
-    extern (C++) const(char)* toChars()
+    extern (C++) const(char)* toChars() const
     {
         OutBuffer buf;
         if (packages && packages.dim)
         {
-            for (size_t i = 0; i < packages.dim; i++)
+            foreach (pid; *packages)
             {
-                Identifier pid = (*packages)[i];
-                buf.writestring(pid.toChars());
+                buf.writestring(pid.toString());
                 buf.writeByte('.');
             }
         }
-        buf.writestring(id.toChars());
+        buf.writestring(id.toString());
         return buf.extractString();
     }
+
+    /// Provide a human readable representation
+    extern (D) const(char)[] toString() const
+    {
+        return this.toChars().toDString;
+    }
 }
diff --git a/src/dmd/globals.h b/src/dmd/globals.h
index 2f1d86c44056..1ed47a94e214 100644
--- a/src/dmd/globals.h
+++ b/src/dmd/globals.h
@@ -15,6 +15,7 @@
 #pragma once
 #endif
 
+#include "root/dcompat.h"
 #include "ctfloat.h"
 #include "outbuffer.h"
 #include "filename.h"
@@ -292,14 +293,6 @@ typedef uint32_t                d_uns32;
 typedef int64_t                 d_int64;
 typedef uint64_t                d_uns64;
 
-// Represents a D [ ] array
-template<typename T>
-struct DArray
-{
-    size_t length;
-    T *ptr;
-};
-
 // file location
 struct Loc
 {
diff --git a/src/dmd/hdrgen.d b/src/dmd/hdrgen.d
index 550a44d563a6..ef0fef36b18c 100644
--- a/src/dmd/hdrgen.d
+++ b/src/dmd/hdrgen.d
@@ -3347,6 +3347,16 @@ extern (C++) const(char)* stcToChars(ref StorageClass stc)
     return null;
 }
 
+
+/**
+ * Returns:
+ *   a human readable representation of `stc`
+ */
+extern (D) const(char)[] stcToString(ref StorageClass stc)
+{
+    return stcToChars(stc).toDString;
+}
+
 extern (C++) void trustToBuffer(OutBuffer* buf, TRUST trust)
 {
     const(char)* p = trustToChars(trust);
@@ -3354,7 +3364,19 @@ extern (C++) void trustToBuffer(OutBuffer* buf, TRUST trust)
         buf.writestring(p);
 }
 
+/**
+ * Returns:
+ *   a human readable representation of `trust`,
+ *   which is the token `trust` corresponds to
+ */
 extern (C++) const(char)* trustToChars(TRUST trust)
+{
+    /// Works because we return a literal
+    return trustToString(trust).ptr;
+}
+
+/// Ditto
+extern (D) string trustToString(TRUST trust)
 {
     final switch (trust)
     {
@@ -3416,7 +3438,18 @@ extern (C++) void protectionToBuffer(OutBuffer* buf, Prot prot)
     }
 }
 
+/**
+ * Returns:
+ *   a human readable representation of `kind`
+ */
 extern (C++) const(char)* protectionToChars(Prot.Kind kind)
+{
+    // Null terminated because we return a literal
+    return protectionToString(kind).ptr;
+}
+
+/// Ditto
+extern (D) string protectionToString(Prot.Kind kind)
 {
     final switch (kind)
     {
diff --git a/src/dmd/identifier.d b/src/dmd/identifier.d
index 3f7a7cd8a425..bd4648a6aa15 100644
--- a/src/dmd/identifier.d
+++ b/src/dmd/identifier.d
@@ -74,7 +74,7 @@ nothrow:
         return name;
     }
 
-    extern (D) const(char)[] toString() const pure
+    extern (D) override const(char)[] toString() const pure
     {
         return name[0 .. len];
     }
diff --git a/src/dmd/json.d b/src/dmd/json.d
index 1937393edee9..d222c623be6a 100644
--- a/src/dmd/json.d
+++ b/src/dmd/json.d
@@ -33,6 +33,8 @@ import dmd.id;
 import dmd.identifier;
 import dmd.mtype;
 import dmd.root.outbuffer;
+import dmd.root.rootobject;
+import dmd.utils;
 import dmd.visitor;
 
 version(Windows) {
@@ -47,13 +49,14 @@ private extern (C++) final class ToJsonVisitor : Visitor
 public:
     OutBuffer* buf;
     int indentLevel;
-    const(char)* filename;
+    const(char)[] filename;
 
     extern (D) this(OutBuffer* buf)
     {
         this.buf = buf;
     }
 
+
     void indent()
     {
         if (buf.offset >= 1 && buf.data[buf.offset - 1] == '\n')
@@ -83,11 +86,10 @@ public:
         buf.writeByte('\"');
     }
 
-    void stringPart(const(char)* s)
+    extern(D) void stringPart(const(char)[] s)
     {
-        for (; *s; s++)
+        foreach (char c; s)
         {
-            char c = cast(char)*s;
             switch (c)
             {
             case '\n':
@@ -128,7 +130,7 @@ public:
     /*********************************
      * Encode string into buf, and wrap it in double quotes.
      */
-    void value(const(char)* s)
+    extern(D) void value(const(char)[] s)
     {
         stringStart();
         stringPart(s);
@@ -153,7 +155,7 @@ public:
     /*********************************
      * Item is an intented value and a comma, for use in arrays
      */
-    void item(const(char)* s)
+    extern(D) void item(const(char)[] s)
     {
         indent();
         value(s);
@@ -221,7 +223,7 @@ public:
     }
 
     // Json object property functions
-    void propertyStart(const(char)* name)
+    extern(D) void propertyStart(const(char)[] name)
     {
         indent();
         value(name);
@@ -235,7 +237,7 @@ public:
      name = the name of the object property
      s = the string value of the object property
     */
-    void property(const(char)* name, const(char)* s)
+    extern(D) void property(const(char)[] name, const(char)[] s)
     {
         if (s is null)
             return;
@@ -251,7 +253,7 @@ public:
      name = the name of the object property
      s = the string value of the object property
     */
-    void requiredProperty(const(char)* name, const(char)* s)
+    extern(D) void requiredProperty(const(char)[] name, const(char)[] s)
     {
         propertyStart(name);
         if (s is null)
@@ -261,21 +263,21 @@ public:
         comma();
     }
 
-    void property(const(char)* name, int i)
+    extern(D) void property(const(char)[] name, int i)
     {
         propertyStart(name);
         value(i);
         comma();
     }
 
-    void propertyBool(const(char)* name, const bool b)
+    extern(D) void propertyBool(const(char)[] name, const bool b)
     {
         propertyStart(name);
         valueBool(b);
         comma();
     }
 
-    void property(const(char)* name, TRUST trust)
+    extern(D) void property(const(char)[] name, TRUST trust)
     {
         final switch (trust)
         {
@@ -295,7 +297,7 @@ public:
         }
     }
 
-    void property(const(char)* name, PURE purity)
+    extern(D) void property(const(char)[] name, PURE purity)
     {
         final switch (purity)
         {
@@ -318,7 +320,7 @@ public:
         }
     }
 
-    void property(const(char)* name, const LINK linkage)
+    extern(D) void property(const(char)[] name, const LINK linkage)
     {
         final switch (linkage)
         {
@@ -352,7 +354,7 @@ public:
         }
     }
 
-    void propertyStorageClass(const(char)* name, StorageClass stc)
+    extern(D) void propertyStorageClass(const(char)[] name, StorageClass stc)
     {
         stc &= STCStorageClass;
         if (stc)
@@ -361,22 +363,21 @@ public:
             arrayStart();
             while (stc)
             {
-                const(char)* p = stcToChars(stc);
-                assert(p);
+                auto p = stcToString(stc);
+                assert(p.length);
                 item(p);
             }
             arrayEnd();
         }
     }
 
-    void property(const(char)* linename, const(char)* charname, Loc* loc)
+    extern(D) void property(const(char)[] linename, const(char)[] charname, Loc* loc)
     {
         if (loc)
         {
-            const(char)* filename = loc.filename;
-            if (filename)
+            if (auto filename = loc.filename.toDString)
             {
-                if (!this.filename || strcmp(filename, this.filename))
+                if (filename != this.filename)
                 {
                     this.filename = filename;
                     property("file", filename);
@@ -391,26 +392,26 @@ public:
         }
     }
 
-    void property(const(char)* name, Type type)
+    extern(D) void property(const(char)[] name, Type type)
     {
         if (type)
         {
-            property(name, type.toChars());
+            property(name, type.toString());
         }
     }
 
-    void property(const(char)* name, const(char)* deconame, Type type)
+    extern(D) void property(const(char)[] name, const(char)[] deconame, Type type)
     {
         if (type)
         {
             if (type.deco)
-                property(deconame, type.deco);
+                property(deconame, type.deco.toDString);
             else
-                property(name, type.toChars());
+                property(name, type.toString());
         }
     }
 
-    void property(const(char)* name, Parameters* parameters)
+    extern(D) void property(const(char)[] name, Parameters* parameters)
     {
         if (parameters is null || parameters.dim == 0)
             return;
@@ -423,11 +424,11 @@ public:
                 Parameter p = (*parameters)[i];
                 objectStart();
                 if (p.ident)
-                    property("name", p.ident.toChars());
+                    property("name", p.ident.toString());
                 property("type", "deco", p.type);
                 propertyStorageClass("storageClass", p.storageClass);
                 if (p.defaultArg)
-                    property("default", p.defaultArg.toChars());
+                    property("default", p.defaultArg.toString());
                 objectEnd();
             }
         }
@@ -441,17 +442,17 @@ public:
             return;
         if (!s.isTemplateDeclaration()) // TemplateDeclaration::kind() acts weird sometimes
         {
-            property("name", s.toChars());
-            property("kind", s.kind());
+            property("name", s.toString());
+            property("kind", s.kind.toDString);
         }
         if (s.prot().kind != Prot.Kind.public_) // TODO: How about package(names)?
-            property("protection", protectionToChars(s.prot().kind));
+            property("protection", protectionToString(s.prot().kind));
         if (EnumMember em = s.isEnumMember())
         {
             if (em.origValue)
-                property("value", em.origValue.toChars());
+                property("value", em.origValue.toString());
         }
-        property("comment", s.comment);
+        property("comment", s.comment.toDString);
         property("line", "char", &s.loc);
     }
 
@@ -466,11 +467,11 @@ public:
         // Emit originalType if it differs from type
         if (d.type != d.originalType && d.originalType)
         {
-            const(char)* ostr = d.originalType.toChars();
+            auto ostr = d.originalType.toString();
             if (d.type)
             {
-                const(char)* tstr = d.type.toChars();
-                if (strcmp(tstr, ostr))
+                auto tstr = d.type.toString();
+                if (ostr != tstr)
                 {
                     //printf("tstr = %s, ostr = %s\n", tstr, ostr);
                     property("originalType", ostr);
@@ -487,7 +488,7 @@ public:
         if (td.onemember && td.onemember.isCtorDeclaration())
             property("name", "this"); // __ctor -> this
         else
-            property("name", td.ident.toChars()); // Foo(T) -> Foo
+            property("name", td.ident.toString()); // Foo(T) -> Foo
     }
 
     /* ========================================================================== */
@@ -499,11 +500,11 @@ public:
     {
         objectStart();
         if (s.md)
-            property("name", s.md.toChars());
-        property("kind", s.kind());
-        filename = s.srcfile.toChars();
+            property("name", s.md.toString());
+        property("kind", s.kind.toDString);
+        filename = s.srcfile.toString();
         property("file", filename);
-        property("comment", s.comment);
+        property("comment", s.comment.toDString);
         propertyStart("members");
         arrayStart();
         for (size_t i = 0; i < s.members.dim; i++)
@@ -526,20 +527,20 @@ public:
             for (size_t i = 0; i < s.packages.dim; i++)
             {
                 Identifier pid = (*s.packages)[i];
-                stringPart(pid.toChars());
+                stringPart(pid.toString());
                 buf.writeByte('.');
             }
         }
-        stringPart(s.id.toChars());
+        stringPart(s.id.toString());
         stringEnd();
         comma();
-        property("kind", s.kind());
-        property("comment", s.comment);
+        property("kind", s.kind.toDString);
+        property("comment", s.comment.toDString);
         property("line", "char", &s.loc);
         if (s.prot().kind != Prot.Kind.public_)
-            property("protection", protectionToChars(s.prot().kind));
+            property("protection", protectionToString(s.prot().kind));
         if (s.aliasId)
-            property("alias", s.aliasId.toChars());
+            property("alias", s.aliasId.toString());
         bool hasRenamed = false;
         bool hasSelective = false;
         for (size_t i = 0; i < s.aliases.dim; i++)
@@ -562,7 +563,7 @@ public:
                 Identifier name = s.names[i];
                 Identifier _alias = s.aliases[i];
                 if (_alias)
-                    property(_alias.toChars(), name.toChars());
+                    property(_alias.toString(), name.toString());
             }
             objectEnd();
         }
@@ -571,11 +572,10 @@ public:
             // import foo : target1;
             propertyStart("selective");
             arrayStart();
-            for (size_t i = 0; i < s.names.dim; i++)
+            foreach (i, name; s.names)
             {
-                Identifier name = s.names[i];
                 if (!s.aliases[i])
-                    item(name.toChars());
+                    item(name.toString());
             }
             arrayEnd();
         }
@@ -634,7 +634,7 @@ public:
         {
             if (cd.baseClass && cd.baseClass.ident != Id.Object)
             {
-                property("base", cd.baseClass.toPrettyChars(true));
+                property("base", cd.baseClass.toPrettyChars(true).toDString);
             }
             if (cd.interfaces.length)
             {
@@ -642,7 +642,7 @@ public:
                 arrayStart();
                 foreach (b; cd.interfaces)
                 {
-                    item(b.sym.toPrettyChars(true));
+                    item(b.sym.toPrettyChars(true).toDString);
                 }
                 arrayEnd();
             }
@@ -676,7 +676,7 @@ public:
             for (size_t i = 0; i < d.foverrides.dim; i++)
             {
                 FuncDeclaration fd = d.foverrides[i];
-                item(fd.toPrettyChars());
+                item(fd.toPrettyChars().toDString);
             }
             arrayEnd();
         }
@@ -705,7 +705,7 @@ public:
         {
             TemplateParameter s = (*d.parameters)[i];
             objectStart();
-            property("name", s.ident.toChars());
+            property("name", s.ident.toString());
             TemplateTypeParameter type = s.isTemplateTypeParameter();
             if (type)
             {
@@ -722,9 +722,9 @@ public:
                 property("kind", "value");
                 property("type", "deco", value.valType);
                 if (value.specValue)
-                    property("specValue", value.specValue.toChars());
+                    property("specValue", value.specValue.toString());
                 if (value.defaultValue)
-                    property("defaultValue", value.defaultValue.toChars());
+                    property("defaultValue", value.defaultValue.toString());
             }
             TemplateAliasParameter _alias = s.isTemplateAliasParameter();
             if (_alias)
@@ -732,9 +732,9 @@ public:
                 property("kind", "alias");
                 property("type", "deco", _alias.specType);
                 if (_alias.specAlias)
-                    property("specAlias", _alias.specAlias.toChars());
+                    property("specAlias", _alias.specAlias.toString());
                 if (_alias.defaultAlias)
-                    property("defaultAlias", _alias.defaultAlias.toChars());
+                    property("defaultAlias", _alias.defaultAlias.toString());
             }
             TemplateTupleParameter tuple = s.isTemplateTupleParameter();
             if (tuple)
@@ -747,7 +747,7 @@ public:
         Expression expression = d.constraint;
         if (expression)
         {
-            property("constraint", expression.toChars());
+            property("constraint", expression.toString());
         }
         propertyStart("members");
         arrayStart();
@@ -806,7 +806,7 @@ public:
         objectStart();
         jsonProperties(d);
         if (d._init)
-            property("init", d._init.toChars());
+            property("init", d._init.toString());
         if (d.isField())
             property("offset", d.offset);
         if (d.alignment && d.alignment != STRUCTALIGN_DEFAULT)
@@ -850,8 +850,8 @@ public:
     private void generateCompilerInfo()
     {
         objectStart();
-        requiredProperty("vendor", global.compiler.vendor);
-        requiredProperty("version", global._version);
+        requiredProperty("vendor", global.compiler.vendor.toDString);
+        requiredProperty("version", global._version.toDString);
         property("__VERSION__", global.versionNumber());
         requiredProperty("interface", determineCompilerInterface());
         property("size_t", size_t.sizeof);
@@ -900,7 +900,7 @@ public:
         {
             foreach (const versionid; *global.versionids)
             {
-                item(versionid.toChars());
+                item(versionid.toString());
             }
         }
         arrayEnd();
@@ -921,10 +921,10 @@ public:
     private void generateBuildInfo()
     {
         objectStart();
-        requiredProperty("cwd", getcwd(null, 0));
-        requiredProperty("argv0", global.params.argv0);
-        requiredProperty("config", global.inifilename);
-        requiredProperty("libName", global.params.libname);
+        requiredProperty("cwd", getcwd(null, 0).toDString);
+        requiredProperty("argv0", global.params.argv0.toDString);
+        requiredProperty("config", global.inifilename.toDString);
+        requiredProperty("libName", global.params.libname.toDString);
 
         propertyStart("importPaths");
         arrayStart();
@@ -932,7 +932,7 @@ public:
         {
             foreach (importPath; *global.params.imppath)
             {
-                item(importPath);
+                item(importPath.toDString);
             }
         }
         arrayEnd();
@@ -941,7 +941,7 @@ public:
         arrayStart();
         foreach (objfile; global.params.objfiles)
         {
-            item(objfile);
+            item(objfile.toDString);
         }
         arrayEnd();
 
@@ -949,7 +949,7 @@ public:
         arrayStart();
         foreach (lib; global.params.libfiles)
         {
-            item(lib);
+            item(lib.toDString);
         }
         arrayEnd();
 
@@ -957,13 +957,13 @@ public:
         arrayStart();
         foreach (ddocFile; global.params.ddocfiles)
         {
-            item(ddocFile);
+            item(ddocFile.toDString);
         }
         arrayEnd();
 
-        requiredProperty("mapFile", global.params.mapfile);
-        requiredProperty("resourceFile", global.params.resfile);
-        requiredProperty("defFile", global.params.deffile);
+        requiredProperty("mapFile", global.params.mapfile.toDString);
+        requiredProperty("resourceFile", global.params.resfile.toDString);
+        requiredProperty("defFile", global.params.deffile.toDString);
 
         objectEnd();
     }
@@ -981,8 +981,8 @@ public:
         foreach (m; Module.amodules)
         {
             objectStart();
-            requiredProperty("name", m.md ? m.md.toChars() : null);
-            requiredProperty("file", m.srcfile.toChars());
+            requiredProperty("name", m.md ? m.md.toString() : null);
+            requiredProperty("file", m.srcfile.toString());
             propertyBool("isRoot", m.isRoot());
             if(m.contentImportedFiles.dim > 0)
             {
@@ -990,7 +990,7 @@ public:
                 arrayStart();
                 foreach (file; m.contentImportedFiles)
                 {
-                    item(file);
+                    item(file.toDString);
                 }
                 arrayEnd();
             }
@@ -1088,7 +1088,7 @@ JsonFieldFlags tryParseJsonField(const(char)* fieldName)
 Determines and returns the compiler interface which is one of `dmd`, `ldc`,
 `gdc` or `sdc`. Returns `null` if no interface can be determined.
 */
-private const(char)* determineCompilerInterface()
+private extern(D) string determineCompilerInterface()
 {
     if (!strcmp(global.compiler.vendor, "Digital Mars D"))
         return "dmd";
diff --git a/src/dmd/module.h b/src/dmd/module.h
index 7482adee9cb7..24dc6f7e2817 100644
--- a/src/dmd/module.h
+++ b/src/dmd/module.h
@@ -177,7 +177,7 @@ struct ModuleDeclaration
     bool isdeprecated;  // if it is a deprecated module
     Expression *msg;
 
-    const char *toChars();
+    const char *toChars() const;
 };
 
 #endif /* DMD_MODULE_H */
diff --git a/src/dmd/root/dcompat.h b/src/dmd/root/dcompat.h
new file mode 100644
index 000000000000..e5026ead7d9d
--- /dev/null
+++ b/src/dmd/root/dcompat.h
@@ -0,0 +1,25 @@
+/* Compiler implementation of the D programming language
+ * Copyright (C) 1999-2018 by The D Language Foundation, All Rights Reserved
+ * written by Walter Bright
+ * http://www.digitalmars.com
+ * Distributed under the Boost Software License, Version 1.0.
+ * http://www.boost.org/LICENSE_1_0.txt
+ * https://github.com/dlang/dmd/blob/master/src/mars.h
+ */
+
+#ifndef DMD_ROOT_DCOMPAT_H
+#define DMD_ROOT_DCOMPAT_H
+
+#ifdef __DMC__
+#pragma once
+#endif
+
+/// Represents a D [ ] array
+template<typename T>
+struct DArray
+{
+    size_t length;
+    T *ptr;
+};
+
+#endif /* DMD_ROOT_DCOMPAT_H */
diff --git a/src/dmd/root/object.h b/src/dmd/root/object.h
index b990693b3d41..e3067e91dbe5 100644
--- a/src/dmd/root/object.h
+++ b/src/dmd/root/object.h
@@ -16,6 +16,7 @@
 #pragma once
 #endif
 
+#include "dcompat.h"
 #include <stddef.h>
 
 typedef size_t hash_t;
@@ -57,6 +58,9 @@ class RootObject
     virtual void print();
 
     virtual const char *toChars();
+    /// This function is `extern(D)` and should not be called from C++,
+    /// as the ABI does not match on some platforms
+    virtual DArray<const char> toString();
     virtual void toBuffer(OutBuffer *buf);
 
     /**
diff --git a/src/dmd/root/outbuffer.d b/src/dmd/root/outbuffer.d
index 4ef3528687a5..1695f889e45d 100644
--- a/src/dmd/root/outbuffer.d
+++ b/src/dmd/root/outbuffer.d
@@ -459,4 +459,3 @@ char[] unsignedToTempString(ulong value, char[] buf, uint radix = 10) @safe
     } while (value);
     return buf[i .. $];
 }
-
diff --git a/src/dmd/root/rootobject.d b/src/dmd/root/rootobject.d
index 44f2d7cdc7e4..7ece1b69836b 100644
--- a/src/dmd/root/rootobject.d
+++ b/src/dmd/root/rootobject.d
@@ -62,6 +62,14 @@ extern (C++) class RootObject
         assert(0);
     }
 
+    ///
+    extern(D) const(char)[] toString()
+    {
+        import core.stdc.string : strlen;
+        auto p = this.toChars();
+        return p[0 .. strlen(p)];
+    }
+
     void toBuffer(OutBuffer* buf) nothrow pure @nogc @safe
     {
         assert(0);
diff --git a/src/dmd/utils.d b/src/dmd/utils.d
index d07ad29d2b67..6c438ba75a4f 100644
--- a/src/dmd/utils.d
+++ b/src/dmd/utils.d
@@ -132,3 +132,9 @@ extern (C++) void escapePath(OutBuffer* buf, const(char)* fname)
         fname++;
     }
 }
+
+/// Slices a `\0`-terminated C-string, excluding the terminator
+const(char)[] toDString (const(char)* s) pure nothrow @nogc
+{
+    return s ? s[0 .. strlen(s)] : null;
+}