Attempt at allowing to use C++ structures in C only code: We use the

CreateAsmStructOffsetsHeader mechanism to generate a header with macros
defined to the sizes of the structures we're interested in and when compiling
in C mode define the structures as "struct { char bytes[size]; }".
It works in principle, but due to how jam works, one would have to specify the
dependency to the generated header for all sources that include it directly or
indirectly.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34441 a95241bf-73f2-0310-859d-f6bbb57e9c96

build/jam/BuildSetup

@@ -389,6 +389,7 @@ HAIKU_PRIVATE_KERNEL_HEADERS =
 	[ PrivateHeaders $(DOT) kernel libroot
 		kernel/boot/platform/$(HAIKU_BOOT_PLATFORM) ]
 	[ ArchHeaders $(HAIKU_ARCH) ]
+	[ FDirName $(HAIKU_COMMON_DEBUG_OBJECT_DIR) system kernel ]
 	$(HAIKU_PRIVATE_SYSTEM_HEADERS)
 ;
 

headers/private/kernel/kernel_c++_structs.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2009, Ingo Weinhold, ingo_weinhold@gmx.de.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _KERNEL_KERNEL_CPP_STRUCTS_H
+#define _KERNEL_KERNEL_CPP_STRUCTS_H
+
+
+#include <util/kernel_c.h>
+
+#include <kernel_c++_struct_sizes.h>
+	// this is the generated defining macros for the structure sizes
+
+
+// in C++ mode include the headers defining the structures
+#ifdef __cplusplus
+#	include <condition_variable.h>
+#endif
+
+// in C mode define the structures
+DEFINE_KERNEL_CPP_STRUCT(ConditionVariable)
+
+
+#endif	// _KERNEL_KERNEL_CPP_STRUCTS_H

headers/private/kernel/util/kernel_c.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2009, Ingo Weinhold, ingo_weinhold@gmx.de.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _KERNEL_UTIL_KERNEL_C_H
+#define _KERNEL_UTIL_KERNEL_C_H
+
+
+/*!	Defines a structure that has the size of a certain C++ structure.
+	\param name The name of the C++ structure.
+	\param flatName The name of the structure to be defined.
+*/
+#define DEFINE_FLAT_KERNEL_CPP_STRUCT(name, flatName)	\
+	struct flatName {									\
+		char	bytes[_KERNEL_CPP_STRUCT_SIZE_##name];	\
+	};
+
+
+/*!	In C mode DEFINE_KERNEL_CPP_STRUCT() defines a struct \a name with the
+	size of the C++ structure of the same name. In C++ it is a no-op.
+*/
+#ifdef __cplusplus
+#	define DEFINE_KERNEL_CPP_STRUCT(name)
+#else
+#	define DEFINE_KERNEL_CPP_STRUCT(name)			\
+		DEFINE_FLAT_KERNEL_CPP_STRUCT(name, name)	\
+		typedef struct name name;
+#endif
+
+
+#endif	/* _KERNEL_UTIL_KERNEL_C_H */

src/system/kernel/Jamfile

@@ -63,6 +63,14 @@ KernelMergeObject kernel_core.o :
 	: $(TARGET_KERNEL_PIC_CCFLAGS)
 ;
 
+# Generate the header defining macros for C++ structure sizes.
+local kernelC++StructSizesHeader = [ FGristFiles kernel_c++_struct_sizes.h ] ;
+TARGET_HDRS on $(kernelC++StructSizesHeader)
+    = [ on $(kernelC++StructSizesHeader) return $(TARGET_HDRS) ]
+        $(TARGET_PRIVATE_KERNEL_HEADERS) ;
+CreateAsmStructOffsetsHeader $(kernelC++StructSizesHeader)
+	: kernel_c++_structs.cpp ;
+
 # We need to specify the dependency on the generated syscalls files explicitly.
 Includes [ FGristFiles syscalls.cpp ]
 	: <syscalls>syscall_dispatcher.h <syscalls>syscall_table.h

src/system/kernel/kernel_c++_structs.cpp

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2009, Ingo Weinhold, ingo_weinhold@gmx.de.
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include <computed_asm_macros.h>
+
+#include <condition_variable.h>
+
+
+// NOTE: Don't include <kernel_c++_structs.h>, since that would result in a
+// circular dependency.
+
+
+#define DEFINE_SIZE_MACRO(name) \
+    DEFINE_COMPUTED_ASM_MACRO(_KERNEL_CPP_STRUCT_SIZE_##name, sizeof(name));
+
+
+void
+dummy()
+{
+	DEFINE_SIZE_MACRO(ConditionVariable)
+}