Fuchsia OS : C++ est-il plus avantageux que C pour le développement d'un microkernel ?

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// Copyright 2016 The Fuchsia Authors 
	// Copyright (c) 2008-2015 Travis Geiselbrecht 
	// 
	// Use of this source code is governed by a MIT-style 
	// license that can be found in the LICENSE file or at 
	// https://opensource.org/licenses/MIT 
  
	/** 
         * @file 
         * @brief  Kernel threading 
         * 
         * This file is the core kernel threading interface. 
         * 
         * @defgroup thread Threads 
         * @{ 
         */ 
	#include <kernel/thread.h> 
  
	#include <arch/exception.h> 
	#include <assert.h> 
	#include <debug.h> 
	#include <err.h> 
	#include <inttypes.h> 
  
	#include <kernel/atomic.h> 
	#include <kernel/dpc.h> 
	#include <kernel/mp.h> 
	#include <kernel/percpu.h> 
	#include <kernel/sched.h> 
	#include <kernel/stats.h> 
	#include <kernel/thread.h> 
	#include <kernel/timer.h> 
  
	#include <lib/counters.h> 
	#include <lib/heap.h> 
	#include <lib/ktrace.h> 
  
	#include <list.h> 
	#include <malloc.h> 
	#include <object/c_user_thread.h> 
	#include <platform.h> 
	#include <printf.h> 
	#include <string.h> 
	#include <target.h> 
	#include <vm/vm.h> 
	#include <zircon/types.h> 
  
	// kernel counters. TODO(cpu): remove LK-era counters 
	// The counters below never decrease. 
	// 
	// counts the number of thread_t succesfully created. 
	KCOUNTER(thread_create_count, "kernel.thread.create"); 
	// counts the number of thread_t joined. Never decreases. 
	KCOUNTER(thread_join_count, "kernel.thread.join"); 
	// counts the number of calls to suspend() that succeeded. 
	KCOUNTER(thread_suspend_count, "kernel.thread.suspend"); 
	// counts the number of calls to resume() that succeeded. 
	KCOUNTER(thread_resume_count, "kernel.thread.resume"); 
  
	/* global thread list */ 
	static struct list_node thread_list = LIST_INITIAL_VALUE(thread_list); 
  
	/* master thread spinlock */ 
	spin_lock_t thread_lock = SPIN_LOCK_INITIAL_VALUE; 
  
	/* local routines */ 
	static void thread_exit_locked(thread_t* current_thread, int retcode) __NO_RETURN; 
	static void thread_do_suspend(void); 
  
	static void init_thread_struct(thread_t* t, const char* name) { 
	    memset(t, 0, sizeof(thread_t)); 
	    t->magic = THREAD_MAGIC; 
	    strlcpy(t->name, name, sizeof(t->name)); 
	    wait_queue_init(&t->retcode_wait_queue); 
	} 
  
	static void initial_thread_func(void) TA_REQ(thread_lock) __NO_RETURN; 
	static void initial_thread_func(void) { 
	    int ret; 
  
	    /* release the thread lock that was implicitly held across the reschedule */ 
	    spin_unlock(&thread_lock); 
	    arch_enable_ints(); 
  
	    thread_t* ct = get_current_thread(); 
	    ret = ct->entry(ct->arg); 
  
	    thread_exit(ret); 
	} 
  
  
	/** 
         * @brief  Create a new thread 
         * 
         * This function creates a new thread.  The thread is initially suspended, so you 
         * need to call thread_resume() to execute it. 
         * 
         * @param  name            Name of thread 
         * @param  entry           Entry point of thread 
         * @param  arg             Arbitrary argument passed to entry() 
         * @param  priority        Execution priority for the thread. 
         * @param  stack_size      Stack size for the thread. 
         * @param  alt_trampoline  If not NULL, an alternate trampoline for the thread 
         *                         to start on. 
         * 
         * Thread priority is an integer from 0 (lowest) to 31 (highest).  Some standard 
         * prioritys are defined in <kernel/thread.h>: 
         * 
         *  HIGHEST_PRIORITY 
         *  DPC_PRIORITY 
         *  HIGH_PRIORITY 
         *  DEFAULT_PRIORITY 
         *  LOW_PRIORITY 
         *  IDLE_PRIORITY 
         *  LOWEST_PRIORITY 
         * 
         * Stack size is typically set to DEFAULT_STACK_SIZE 
         * 
         * @return  Pointer to thread object, or NULL on failure. 
         */ 
	thread_t* thread_create_etc( 
	    thread_t* t, 
	    const char* name, 
	    thread_start_routine entry, void* arg, 
	    int priority, 
	    void* stack, void* unsafe_stack, size_t stack_size, 
	    thread_trampoline_routine alt_trampoline) { 
	    unsigned int flags = 0; 
  
	    if (!t) { 
	        <span style="font-family: monospace; padding: 2px; background: #ddd; display: inline-block">t = malloc(sizeof(thread_t));  // allocation dynamique …</span>	        
                    if (!t) 
	            return NULL; 
	        flags |= THREAD_FLAG_FREE_STRUCT; 
	    } 
  
	    init_thread_struct(t, name); 
  
	    t->entry = entry; 
	    t->arg = arg; 
	    t->state = THREAD_INITIAL; 
	    t->signals = 0; 
	    t->blocking_wait_queue = NULL; 
	    t->blocked_status = ZX_OK; 
	    t->interruptable = false; 
	    t->curr_cpu = INVALID_CPU; 
	    t->last_cpu = INVALID_CPU; 
	    t->cpu_affinity = CPU_MASK_ALL; 
  
	    t->retcode = 0; 
	    wait_queue_init(&t->retcode_wait_queue); 
  
	    sched_init_thread(t, priority); 
  
	    /* create the stack */ 
	    if (!stack) { 
	        if (THREAD_STACK_BOUNDS_CHECK) { 
	            stack_size += THREAD_STACK_PADDING_SIZE; 
	            flags |= THREAD_FLAG_DEBUG_STACK_BOUNDS_CHECK; 
	        } 
	        t->stack = malloc(stack_size); 
	        if (!t->stack) { 
	            if (flags & THREAD_FLAG_FREE_STRUCT) 
	                free(t); 
	            return NULL; 
	        } 
	        flags |= THREAD_FLAG_FREE_STACK; 
	        if (THREAD_STACK_BOUNDS_CHECK) { 
	            memset(t->stack, STACK_DEBUG_BYTE, THREAD_STACK_PADDING_SIZE); 
	        } 
	    } else { 
	        t->stack = stack; 
	    } 
  
	#if __has_feature(safe_stack) 
	    if (!unsafe_stack) { 
	        DEBUG_ASSERT(!stack); 
	        DEBUG_ASSERT(flags & THREAD_FLAG_FREE_STACK); 
	        t->unsafe_stack = malloc(stack_size); 
	        if (!t->unsafe_stack) { 
	            free(t->stack); 
	            if (flags & THREAD_FLAG_FREE_STRUCT) 
	                free(t); 
	            return NULL; 
	        } 
	        if (THREAD_STACK_BOUNDS_CHECK) { 
	            memset(t->unsafe_stack, STACK_DEBUG_BYTE, THREAD_STACK_PADDING_SIZE); 
	        } 
	    } else { 
	        DEBUG_ASSERT(stack); 
	        t->unsafe_stack = unsafe_stack; 
	    } 
	#else 
	    DEBUG_ASSERT(!unsafe_stack); 
	#endif 
  
	    t->stack_size = stack_size; 
  
	    /* save whether or not we need to free the thread struct and/or stack */ 
	    t->flags = flags; 
  
	    if (likely(alt_trampoline == NULL)) { 
	        alt_trampoline = initial_thread_func; 
	    } 
  
	    /* set up the initial stack frame */ 
	    arch_thread_initialize(t, (vaddr_t)alt_trampoline); 
  
	    /* add it to the global thread list */ 
	    THREAD_LOCK(state); 
	    list_add_head(&thread_list, &t->thread_list_node); 
	    THREAD_UNLOCK(state); 
  
	    kcounter_add(thread_create_count, 1u); 
	    return t; 
	}