freebsd_network: Remove the need for <kernel_c++_structs.h>.

Use sizeof()+roundup() to build a char[] of the correct size,
and add a static_assert to ensure it stays so.

The <kernel_c++_structs.h> header needs to have its dependency
manually declared, and not all consumers of this file properly
declared it as such. This then fixes a concurrent build problem.

Fixes #17965 as this was the only consumer of this header.

src/libs/compat/freebsd_network/Jamfile

@@ -6,10 +6,6 @@ UsePrivateHeaders net ;
 UsePrivateKernelHeaders ;
 UseHeaders $(HAIKU_PRIVATE_KERNEL_HEADERS) : true ;
 
-# Enabling C++ structures in C only code
-Includes [ FGristFiles kernel_c++_structs.h ]
-	: <src!system!kernel>kernel_c++_struct_sizes.h ;
-
 SubDirCcFlags [ FDefines _KERNEL=1 ] ;
 SubDirC++Flags [ FDefines _KERNEL=1 ] ;
 

src/libs/compat/freebsd_network/compat/sys/condvar.h

@@ -1,20 +1,28 @@
 /*
- * Copyright 2009, Colin Günther, coling@gmx.de.
- * All rights reserved. Distributed under the terms of the MIT License.
+ * Copyright 2023, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
  */
 #ifndef _FBSD_COMPAT_SYS_CONDVAR_H_
 #define _FBSD_COMPAT_SYS_CONDVAR_H_
 
 
-#include <kernel_c++_structs.h>
+#include <sys/param.h>
+#include <KernelExport.h>
+
 
 __BEGIN_DECLS
 
 
 struct cv {
-	struct ConditionVariable condition;
+	// We cannot include <condition_variable.h> here as it is C++-only.
+	char condition[roundup((sizeof(void*) * 5) + sizeof(spinlock) + sizeof(int32), sizeof(void*))];
 };
 
+#ifdef __cplusplus
+#	define __cv_ConditionVariable(CV) reinterpret_cast<ConditionVariable*>(&(CV)->condition)
+#endif
+
+
 void cv_init(struct cv*, const char*);
 void cv_destroy(struct cv*);
 void cv_wait(struct cv*, struct mtx*);
@@ -24,4 +32,5 @@ void cv_signal(struct cv*);
 
 __END_DECLS
 
+
 #endif /* _FBSD_COMPAT_SYS_CONDVAR_H_ */

src/libs/compat/freebsd_network/condvar.cpp

@@ -1,27 +1,32 @@
 /*
- * Copyright 2022, Haiku, Inc. All rights reserved.
+ * Copyright 2022-2023, Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT license.
  */
 
 extern "C" {
 #include <compat/sys/mutex.h>
 #include <compat/sys/kernel.h>
+#include <compat/sys/condvar.h>
 }
 
-#include <compat/sys/condvar.h>
+#include <condition_variable.h>
+
+
+static_assert(sizeof(cv::condition) == sizeof(ConditionVariable));
 
 
 void
 cv_init(struct cv* variable, const char* description)
 {
-	variable->condition.Init(NULL, description);
+	__cv_ConditionVariable(variable)->Init(NULL, description);
 }
 
 
 void
 cv_destroy(struct cv* variable)
 {
-	variable->condition.NotifyAll();
+	__cv_ConditionVariable(variable)->NotifyAll();
+
 	// Nothing else to do.
 }
 
@@ -29,27 +34,28 @@ cv_destroy(struct cv* variable)
 void
 cv_signal(struct cv* variable)
 {
-	variable->condition.NotifyOne();
+	__cv_ConditionVariable(variable)->NotifyOne();
 }
 
 
 int
 cv_timedwait(struct cv* variable, struct mtx* mutex, int timeout)
 {
-	int status;
+	ConditionVariable* condition = __cv_ConditionVariable(variable);
 
 	const uint32 flags = timeout ? B_RELATIVE_TIMEOUT : 0;
 	const bigtime_t bigtimeout = TICKS_2_USEC(timeout);
+	int status;
 
 	if (mutex->type == MTX_RECURSE) {
 		// Special case: let the ConditionVariable handle switching recursive locks.
-		status = variable->condition.Wait(&mutex->u.recursive,
+		status = condition->Wait(&mutex->u.recursive,
 			flags, bigtimeout);
 		return status;
 	}
 
 	ConditionVariableEntry entry;
-	variable->condition.Add(&entry);
+	condition->Add(&entry);
 
 	mtx_unlock(mutex);
 

src/libs/compat/freebsd_network/synch.cpp

@@ -3,10 +3,14 @@
  * Distributed under the terms of the MIT license.
  */
 
+extern "C" {
 #include <compat/sys/systm.h>
 #include <compat/sys/kernel.h>
 #include <compat/sys/mutex.h>
 #include <compat/sys/condvar.h>
+}
+
+#include <condition_variable.h>
 
 
 int
@@ -14,11 +18,11 @@ msleep(void* identifier, struct mtx* mutex, int priority,
 	const char* description, int timeout)
 {
 	struct cv channel;
-	channel.condition.Publish(identifier, description);
+	__cv_ConditionVariable(&channel)->Publish(identifier, description);
 
 	int status = cv_timedwait(&channel, mutex, timeout);
 
-	channel.condition.Unpublish();
+	__cv_ConditionVariable(&channel)->Unpublish();
 	return status;
 }