add -version=cpp98 to compiler

Author: WalterBright

changelog/cpp98.dd

@@ -0,0 +1,57 @@
+## Transition to C++11 character types
+
+        With C++11 comes the advent of changed character type mangling.
+        D's default behavior is now to conform to this. However, this
+        will break existing code. Therefore, the old behavior can be
+        retained by using the -version=Cpp98 compiler switch.
+        For Win32 compilations using Digital Mars C++, -version=Cpp98 will
+        be predefined.
+
+        Of particular note is the new difference between wchar and wchar_t on
+        Windows. This will manifest itself as compile errors when
+        interfacing wchar* with wchar_t* code when calling the Windows API.
+        A cast will resolve the issue.
+
+        Going forward we recommend using WCHAR instead of wchar or wchar_t
+        when interfacing to Windows API functions. (WCHAR is Microsoft
+        Windows' 16 bit character type.)
+
+### C++ Type Equivalence
+
+#### Cpp98 behavior:
+
+        D       Posix           DMC++ Windows   VC++ Windows
+
+        wchar   unsigned short  wchar_t         wchar_t
+        dchar   wchar_t         unsigned        unsigned
+        wchar_t wchar_t         wchar_t         wchar_t
+        WCHAR   --              wchar_t         wchar_t
+
+#### New behavior:
+
+        D       Posix           DMC++ Windows   VC++ Windows
+
+        wchar   char16_t        wchar_t         char16_t
+        dchar   char32_t        unsigned        char32_t
+        wchar_t wchar_t         wchar           wchar_t
+        WCHAR   --              wchar           wchar_t
+
+
+### Name Mangling:
+
+#### Cpp98 behavior:
+
+        D       Posix   DMC++ Windows   VC++ Windows
+
+        wchar   t       _Y              _W
+        dchar   w       I               I
+        wchar_t w       _Y              _W
+
+#### New behavior:
+
+        D       Posix   DMC++ Windows   VC++ Windows
+
+        wchar   Ds      _Y              _S
+        dchar   Di      I               _U
+        wchar_t w       _Y              _W
+

src/dmd/cond.d

@@ -658,6 +658,7 @@ extern (C++) final class VersionCondition : DVCondition
             case "CppRuntime_Gcc":
             case "CppRuntime_Microsoft":
             case "CppRuntime_Sun":
+            case "Cpp98":
             case "unittest":
             case "assert":
             case "all":

src/dmd/globals.d

@@ -149,6 +149,7 @@ struct Param
                             // https://issues.dlang.org/show_bug.cgi?id=16997
     bool fixAliasThis;      // if the current scope has an alias this, check it before searching upper scopes
     bool vsafe;             // use enhanced @safe checking
+    bool cpp98;             // follow C++98 type system issues rather than C++11
     bool ehnogc;            // use @nogc exception handling
     bool dtorFields;        // destruct fields of partially constructed objects
                             // https://issues.dlang.org/show_bug.cgi?id=14246

src/dmd/globals.h

@@ -123,7 +123,8 @@ struct Param
     bool fix16997;      // fix integral promotions for unary + - ~ operators
                         // https://issues.dlang.org/show_bug.cgi?id=16997
     bool vsafe;         // use enhanced @safe checking
-    bool ehnogc;        // use @nogc exception handling
+    bool cpp98;             // follow C++98 type system issues rather than C++11
+    bool ehnogc;            // use @nogc exception handling
     bool dtorFields;        // destruct fields of partially constructed objects
                             // https://issues.dlang.org/show_bug.cgi?id=14246
     bool showGaggedErrors;  // print gagged errors anyway

src/dmd/mars.d

@@ -387,6 +387,13 @@ private int tryMain(size_t argc, const(char)** argv)
         global.params.useExceptions = false;
     }
 
+    /* TEMPORARILY set this to true until the runtime library is updated,
+     * in order to not leave the system in an unbuildable state.
+     */
+    global.params.cpp98 = true;
+
+    if (global.params.isWindows && !global.params.mscoff)
+        global.params.cpp98 = true;             // DMC++ is a C++98 compiler
 
     if (!global.params.obj || global.params.lib)
         global.params.link = false;
@@ -1235,6 +1242,9 @@ void addDefaultVersionIdentifiers(const ref Param params)
     VersionCondition.addPredefinedGlobalIdent("D_Version2");
     VersionCondition.addPredefinedGlobalIdent("all");
 
+    if (params.cpp98)
+        VersionCondition.addPredefinedGlobalIdent("Cpp98");
+
     if (params.cpu >= CPU.sse2)
     {
         VersionCondition.addPredefinedGlobalIdent("D_SIMD");
@@ -2053,9 +2063,14 @@ bool parseCommandLine(const ref Strings arguments, const size_t argc, ref Param
                 }
                 else if (Identifier.isValidIdentifier(p + 9))
                 {
-                    if (!params.versionids)
-                        params.versionids = new Array!(const(char)*);
-                    params.versionids.push(p + 9);
+                    if (strcmp(p + 9, "Cpp98") == 0)    // -version=Cpp98
+                        params.cpp98 = true;            // version will be set in addDefaultVersionIdentifiers()
+                    else
+                    {
+                        if (!params.versionids)
+                            params.versionids = new Array!(const(char)*);
+                        params.versionids.push(p + 9);
+                    }
                 }
                 else
                     goto Lerror;

test/fail_compilation/reserved_version.d

@@ -105,6 +105,7 @@ fail_compilation/reserved_version.d(206): Error: version identifier `CppRuntime_
 fail_compilation/reserved_version.d(207): Error: version identifier `CppRuntime_Gcc` is reserved and cannot be set
 fail_compilation/reserved_version.d(208): Error: version identifier `CppRuntime_Microsoft` is reserved and cannot be set
 fail_compilation/reserved_version.d(209): Error: version identifier `CppRuntime_Sun` is reserved and cannot be set
+fail_compilation/reserved_version.d(210): Error: version identifier `Cpp98` is reserved and cannot be set
 ---
 */
 
@@ -216,6 +217,7 @@ version = CppRuntime_DigitalMars;
 version = CppRuntime_Gcc;
 version = CppRuntime_Microsoft;
 version = CppRuntime_Sun;
+version = Cpp98;
 
 // This should work though
 debug = DigitalMars;
@@ -300,6 +302,7 @@ debug = CppRuntime_DigitalMars;
 debug = CppRuntime_Gcc;
 debug = CppRuntime_Microsoft;
 debug = CppRuntime_Sun;
+debug = Cpp98;
 debug = D_Coverage;
 debug = D_Ddoc;
 debug = D_InlineAsm_X86;

test/fail_compilation/reserved_version_switch.d

@@ -82,6 +82,7 @@
 // REQUIRED_ARGS: -version=CppRuntime_Gcc
 // REQUIRED_ARGS: -version=CppRuntime_Microsoft
 // REQUIRED_ARGS: -version=CppRuntime_Sun
+// REQUIRED_ARGS: -version=Cpp98
 // REQUIRED_ARGS: -version=D_Coverage
 // REQUIRED_ARGS: -version=D_Ddoc
 // REQUIRED_ARGS: -version=D_InlineAsm_X86
@@ -178,6 +179,7 @@
 // REQUIRED_ARGS: -debug=CppRuntime_Gcc
 // REQUIRED_ARGS: -debug=CppRuntime_Microsoft
 // REQUIRED_ARGS: -debug=CppRuntime_Sun
+// REQUIRED_ARGS: -debug=Cpp98
 // REQUIRED_ARGS: -debug=D_Coverage
 // REQUIRED_ARGS: -debug=D_Ddoc
 // REQUIRED_ARGS: -debug=D_InlineAsm_X86