From e2a2ae12d75e4d6afbf3babafd9fde6438997243 Mon Sep 17 00:00:00 2001
From: Walter Bright <walter@walterbright.com>
Date: Sun, 2 Dec 2018 02:26:50 -0800
Subject: [PATCH] add -version=cpp98 to compiler

---
 changelog/cpp98.dd | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 src/dmd/cond.d     |  1 +
 src/dmd/globals.d  |  1 +
 src/dmd/globals.h  |  3 ++-
 src/dmd/mars.d     | 16 ++++++++++---
 5 files changed, 73 insertions(+), 4 deletions(-)
 create mode 100644 changelog/cpp98.dd

diff --git a/changelog/cpp98.dd b/changelog/cpp98.dd
new file mode 100644
index 000000000000..c63f90eb7b64
--- /dev/null
+++ b/changelog/cpp98.dd
@@ -0,0 +1,56 @@
+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:
+
+		Posix	DMC++ Windows	VC++ Windows
+	wchar	Ds	_Y		_S
+	dchar	Di	I		_U
+	wchar_t	w	_Y		_W
+
diff --git a/src/dmd/cond.d b/src/dmd/cond.d
index ef823db9abc1..189dc9de89c3 100644
--- a/src/dmd/cond.d
+++ b/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":
diff --git a/src/dmd/globals.d b/src/dmd/globals.d
index 6e475694229e..5e5e24e13004 100644
--- a/src/dmd/globals.d
+++ b/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
diff --git a/src/dmd/globals.h b/src/dmd/globals.h
index 336deae5481c..43c1ba0b614e 100644
--- a/src/dmd/globals.h
+++ b/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
diff --git a/src/dmd/mars.d b/src/dmd/mars.d
index 8e70f9728a11..8b574aff3cb6 100644
--- a/src/dmd/mars.d
+++ b/src/dmd/mars.d
@@ -387,6 +387,8 @@ private int tryMain(size_t argc, const(char)** argv)
         global.params.useExceptions = false;
     }
 
+    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 +1237,9 @@ 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 +2058,14 @@ 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;