Merge pull request #10801 from MoonlightSentinel/headers

Add C++ header generation

changelog/headers.dd

@@ -0,0 +1,104 @@
+Added experimental `C++` header generation from `extern(C|C++)` declarations
+
+DMD can now write C++ header files which contain bindings for declarations
+in existing D files that were marked as `extern(C)` or `extern(C++)`.
+
+This feature is available via the following command line switches:
+- `-HC`: Write the generated headers to standard output
+- `-HCf=<file>`: Write the generated headers to file
+- `-HCd=<directory>`: Write the generated headers to file (not implemented yet)
+
+Consider the following example:
+
+```
+module a;
+
+extern(C) int foo(int a) { ... }
+extern(C++) void bar() { ... }
+void ignored() { ... }
+```
+```
+module b;
+
+extern (C++) struct S
+{
+    string name;
+    this (string name) { ... }
+    bool bar() { ... }
+}
+```
+```
+module c;
+
+import a, b;
+
+extern (C++) class C
+{
+    S[] s;
+    this () {}
+    bool bar() { ...}
+}
+
+```
+
+Compiling these modules with `dmd -c -o- -HC a.d b.d c.d` will generate the following header:
+
+```
+#pragma once
+
+// Automatically generated by dmd -HC
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+#define _d_void void
+#define _d_bool bool
+#define _d_byte signed char
+#define _d_ubyte unsigned char
+#define _d_short short
+#define _d_ushort unsigned short
+#define _d_int int
+#define _d_uint unsigned
+#define _d_long long long
+#define _d_ulong unsigned long long
+#define _d_float float
+#define _d_double double
+#define _d_real long double
+#define _d_char char
+#define _d_wchar wchar_t
+#define _d_dchar unsigned
+typedef _d_long d_int64;
+#define _d_null NULL
+
+// Parsing module a
+// Parsing module b
+// Parsing module c
+struct S;
+extern "C" _d_int foo(_d_int a);
+
+extern _d_void bar();
+
+// ignoring function a.ignored because of linkage
+struct S
+{
+    DArray< _d_char > name;
+    S(DArray< _d_char > name);
+    _d_bool bar();
+    S() : name() {}
+};
+
+class C
+{
+public:
+    DArray< S > s;
+    C();
+    virtual _d_bool bar();
+};
+```
+
+Refer to the $(LINK2 $(ROOT_DIR)/spec/cpp_interface.html, documentation) for further information regarding C++ interoperation.
+
+Note that this feature is considered experimental and might not work correctly sometimes.
+Please open an issue in the $(LINK2 https://issues.dlang.org, bug tracker) if you encounter a bug while using this feature.

src/build.d

@@ -1154,7 +1154,7 @@ auto sourceFiles()
             cli.d clone.d compiler.d complex.d cond.d constfold.d cppmangle.d cppmanglewin.d ctfeexpr.d
             ctorflow.d dcast.d dclass.d declaration.d delegatize.d denum.d dimport.d dinifile.d
             dinterpret.d dmacro.d dmangle.d dmodule.d doc.d dscope.d dstruct.d dsymbol.d dsymbolsem.d
-            dtemplate.d dversion.d env.d escape.d expression.d expressionsem.d func.d hdrgen.d impcnvtab.d
+            dtemplate.d dtoh.d dversion.d env.d escape.d expression.d expressionsem.d func.d hdrgen.d impcnvtab.d
             imphint.d init.d initsem.d inline.d inlinecost.d intrange.d json.d lambdacomp.d lib.d libelf.d
             libmach.d libmscoff.d libomf.d link.d mars.d mtype.d nogc.d nspace.d ob.d objc.d opover.d optimize.d
             parse.d parsetimevisitor.d permissivevisitor.d printast.d safe.d sapply.d scanelf.d scanmach.d

src/dmd/cli.d

@@ -370,6 +370,15 @@ dmd -cov -unittest myprog.d
         Option("Hf=<filename>",
             "write 'header' file to filename"
         ),
+        Option("HC",
+            "generate C++ 'header' file"
+        ),
+        Option("HCd=<directory>",
+            "write C++ 'header' file to directory"
+        ),
+        Option("HCf=<filename>",
+            "write C++ 'header' file to filename"
+        ),
         Option("-help",
             "print help and exit"
         ),