/* * tclWinThread.c -- * * This file implements the Windows-specific thread operations. * * Copyright (c) 1998 by Sun Microsystems, Inc. * Copyright (c) 1999 by Scriptics Corporation * Copyright (c) 2008 by George Peter Staplin * * See the file "license.terms" for information on usage and redistribution of * this file, and for a DISCLAIMER OF ALL WARRANTIES. */ #include "tclWinInt.h" #include /* Workaround for mingw versions which don't provide this in float.h */ #ifndef _MCW_EM # define _MCW_EM 0x0008001F /* Error masks */ # define _MCW_RC 0x00000300 /* Rounding */ # define _MCW_PC 0x00030000 /* Precision */ _CRTIMP unsigned int __cdecl _controlfp (unsigned int unNew, unsigned int unMask); #endif /* * This is the master lock used to serialize access to other serialization * data structures. */ static CRITICAL_SECTION masterLock; static int initialized = 0; /* * This is the master lock used to serialize initialization and finalization * of Tcl as a whole. */ static CRITICAL_SECTION initLock; /* * allocLock is used by Tcl's version of malloc for synchronization. For * obvious reasons, cannot use any dyamically allocated storage. */ #ifdef TCL_THREADS static struct Tcl_Mutex_ { CRITICAL_SECTION crit; } allocLock; static Tcl_Mutex allocLockPtr = &allocLock; static int allocOnce = 0; #endif /* TCL_THREADS */ /* * The joinLock serializes Create- and ExitThread. This is necessary to * prevent a race where a new joinable thread exits before the creating thread * had the time to create the necessary data structures in the emulation * layer. */ static CRITICAL_SECTION joinLock; /* * Condition variables are implemented with a combination of a per-thread * Windows Event and a per-condition waiting queue. The idea is that each * thread has its own Event that it waits on when it is doing a ConditionWait; * it uses the same event for all condition variables because it only waits on * one at a time. Each condition variable has a queue of waiting threads, and * a mutex used to serialize access to this queue. * * Special thanks to David Nichols and Jim Davidson for advice on the * Condition Variable implementation. */ /* * The per-thread event and queue pointers. */ #ifdef TCL_THREADS typedef struct ThreadSpecificData { HANDLE condEvent; /* Per-thread condition event */ struct ThreadSpecificData *nextPtr; /* Queue pointers */ struct ThreadSpecificData *prevPtr; int flags; /* See flags below */ } ThreadSpecificData; static Tcl_ThreadDataKey dataKey; #endif /* TCL_THREADS */ /* * State bits for the thread. * WIN_THREAD_UNINIT Uninitialized. Must be zero because of the way * ThreadSpecificData is created. * WIN_THREAD_RUNNING Running, not waiting. * WIN_THREAD_BLOCKED Waiting, or trying to wait. */ #define WIN_THREAD_UNINIT 0x0 #define WIN_THREAD_RUNNING 0x1 #define WIN_THREAD_BLOCKED 0x2 /* * The per condition queue pointers and the Mutex used to serialize access to * the queue. */ typedef struct { CRITICAL_SECTION condLock; /* Lock to serialize queuing on the * condition. */ struct ThreadSpecificData *firstPtr; /* Queue pointers */ struct ThreadSpecificData *lastPtr; } WinCondition; /* * Additions by AOL for specialized thread memory allocator. */ #ifdef USE_THREAD_ALLOC static DWORD tlsKey; typedef struct { Tcl_Mutex tlock; CRITICAL_SECTION wlock; } allocMutex; #endif /* USE_THREAD_ALLOC */ /* * The per thread data passed from TclpThreadCreate * to TclWinThreadStart. */ typedef struct { LPTHREAD_START_ROUTINE lpStartAddress; /* Original startup routine */ LPVOID lpParameter; /* Original startup data */ unsigned int fpControl; /* Floating point control word from the * main thread */ } WinThread; /* *---------------------------------------------------------------------- * * TclWinThreadStart -- * * This procedure is the entry point for all new threads created * by Tcl on Windows. * * Results: * Various, depending on the result of the wrapped thread start * routine. * * Side effects: * Arbitrary, since user code is executed. * *---------------------------------------------------------------------- */ static DWORD WINAPI TclWinThreadStart( LPVOID lpParameter) /* The WinThread structure pointer passed * from TclpThreadCreate */ { WinThread *winThreadPtr = (WinThread *) lpParameter; LPTHREAD_START_ROUTINE lpOrigStartAddress; LPVOID lpOrigParameter; if (!winThreadPtr) { return TCL_ERROR; } _controlfp(winThreadPtr->fpControl, _MCW_EM | _MCW_RC | 0x03000000 /* _MCW_DN */ #if !defined(_WIN64) | _MCW_PC #endif ); lpOrigStartAddress = winThreadPtr->lpStartAddress; lpOrigParameter = winThreadPtr->lpParameter; ckfree((char *)winThreadPtr); return lpOrigStartAddress(lpOrigParameter); } /* *---------------------------------------------------------------------- * * TclpThreadCreate -- * * This procedure creates a new thread. * * Results: * TCL_OK if the thread could be created. The thread ID is returned in a * parameter. * * Side effects: * A new thread is created. * *---------------------------------------------------------------------- */ int TclpThreadCreate( Tcl_ThreadId *idPtr, /* Return, the ID of the thread. */ Tcl_ThreadCreateProc *proc, /* Main() function of the thread. */ ClientData clientData, /* The one argument to Main(). */ int stackSize, /* Size of stack for the new thread. */ int flags) /* Flags controlling behaviour of the new * thread. */ { WinThread *winThreadPtr; /* Per-thread startup info */ HANDLE tHandle; winThreadPtr = (WinThread *)ckalloc(sizeof(WinThread)); winThreadPtr->lpStartAddress = (LPTHREAD_START_ROUTINE) proc; winThreadPtr->lpParameter = clientData; winThreadPtr->fpControl = _controlfp(0, 0); EnterCriticalSection(&joinLock); *idPtr = 0; /* must initialize as Tcl_Thread is a pointer and * on WIN64 sizeof void* != sizeof unsigned */ #if defined(_MSC_VER) || defined(__MSVCRT__) || defined(__BORLANDC__) tHandle = (HANDLE) _beginthreadex(NULL, (unsigned) stackSize, (Tcl_ThreadCreateProc*) TclWinThreadStart, winThreadPtr, 0, (unsigned *)idPtr); #else tHandle = CreateThread(NULL, (DWORD) stackSize, TclWinThreadStart, winThreadPtr, 0, (LPDWORD)idPtr); #endif if (tHandle == NULL) { LeaveCriticalSection(&joinLock); return TCL_ERROR; } else { if (flags & TCL_THREAD_JOINABLE) { TclRememberJoinableThread(*idPtr); } /* * The only purpose of this is to decrement the reference count so the * OS resources will be reaquired when the thread closes. */ CloseHandle(tHandle); LeaveCriticalSection(&joinLock); return TCL_OK; } } /* *---------------------------------------------------------------------- * * Tcl_JoinThread -- * * This procedure waits upon the exit of the specified thread. * * Results: * TCL_OK if the wait was successful, TCL_ERROR else. * * Side effects: * The result area is set to the exit code of the thread we * waited upon. * *---------------------------------------------------------------------- */ int Tcl_JoinThread( Tcl_ThreadId threadId, /* Id of the thread to wait upon */ int *result) /* Reference to the storage the result of the * thread we wait upon will be written into. */ { return TclJoinThread(threadId, result); } /* *---------------------------------------------------------------------- * * TclpThreadExit -- * * This procedure terminates the current thread. * * Results: * None. * * Side effects: * This procedure terminates the current thread. * *---------------------------------------------------------------------- */ void TclpThreadExit( int status) { EnterCriticalSection(&joinLock); TclSignalExitThread(Tcl_GetCurrentThread(), status); LeaveCriticalSection(&joinLock); #if defined(_MSC_VER) || defined(__MSVCRT__) || defined(__BORLANDC__) _endthreadex((unsigned) status); #else ExitThread((DWORD) status); #endif } /* *---------------------------------------------------------------------- * * Tcl_GetCurrentThread -- * * This procedure returns the ID of the currently running thread. * * Results: * A thread ID. * * Side effects: * None. * *---------------------------------------------------------------------- */ Tcl_ThreadId Tcl_GetCurrentThread(void) { return (Tcl_ThreadId)(size_t)GetCurrentThreadId(); } /* *---------------------------------------------------------------------- * * TclpInitLock * * This procedure is used to grab a lock that serializes initialization * and finalization of Tcl. On some platforms this may also initialize * the mutex used to serialize creation of more mutexes and thread local * storage keys. * * Results: * None. * * Side effects: * Acquire the initialization mutex. * *---------------------------------------------------------------------- */ void TclpInitLock(void) { if (!initialized) { /* * There is a fundamental race here that is solved by creating the * first Tcl interpreter in a single threaded environment. Once the * interpreter has been created, it is safe to create more threads * that create interpreters in parallel. */ initialized = 1; InitializeCriticalSection(&joinLock); InitializeCriticalSection(&initLock); InitializeCriticalSection(&masterLock); } EnterCriticalSection(&initLock); } /* *---------------------------------------------------------------------- * * TclpInitUnlock * * This procedure is used to release a lock that serializes * initialization and finalization of Tcl. * * Results: * None. * * Side effects: * Release the initialization mutex. * *---------------------------------------------------------------------- */ void TclpInitUnlock(void) { LeaveCriticalSection(&initLock); } /* *---------------------------------------------------------------------- * * TclpMasterLock * * This procedure is used to grab a lock that serializes creation of * mutexes, condition variables, and thread local storage keys. * * This lock must be different than the initLock because the initLock is * held during creation of syncronization objects. * * Results: * None. * * Side effects: * Acquire the master mutex. * *---------------------------------------------------------------------- */ void TclpMasterLock(void) { if (!initialized) { /* * There is a fundamental race here that is solved by creating the * first Tcl interpreter in a single threaded environment. Once the * interpreter has been created, it is safe to create more threads * that create interpreters in parallel. */ initialized = 1; InitializeCriticalSection(&joinLock); InitializeCriticalSection(&initLock); InitializeCriticalSection(&masterLock); } EnterCriticalSection(&masterLock); } /* *---------------------------------------------------------------------- * * TclpMasterUnlock * * This procedure is used to release a lock that serializes creation and * deletion of synchronization objects. * * Results: * None. * * Side effects: * Release the master mutex. * *---------------------------------------------------------------------- */ void TclpMasterUnlock(void) { LeaveCriticalSection(&masterLock); } /* *---------------------------------------------------------------------- * * Tcl_GetAllocMutex * * This procedure returns a pointer to a statically initialized mutex for * use by the memory allocator. The alloctor must use this lock, because * all other locks are allocated... * * Results: * A pointer to a mutex that is suitable for passing to Tcl_MutexLock and * Tcl_MutexUnlock. * * Side effects: * None. * *---------------------------------------------------------------------- */ Tcl_Mutex * Tcl_GetAllocMutex(void) { #ifdef TCL_THREADS if (!allocOnce) { InitializeCriticalSection(&allocLock.crit); allocOnce = 1; } return &allocLockPtr; #else return NULL; #endif } /* *---------------------------------------------------------------------- * * TclFinalizeLock * * This procedure is used to destroy all private resources used in this * file. * * Results: * None. * * Side effects: * Destroys everything private. TclpInitLock must be held entering this * function. * *---------------------------------------------------------------------- */ void TclFinalizeLock(void) { TclpMasterLock(); DeleteCriticalSection(&joinLock); /* * Destroy the critical section that we are holding! */ DeleteCriticalSection(&masterLock); initialized = 0; #ifdef TCL_THREADS if (allocOnce) { DeleteCriticalSection(&allocLock.crit); allocOnce = 0; } #endif LeaveCriticalSection(&initLock); /* * Destroy the critical section that we were holding. */ DeleteCriticalSection(&initLock); } #ifdef TCL_THREADS /* locally used prototype */ static void FinalizeConditionEvent(ClientData data); /* *---------------------------------------------------------------------- * * Tcl_MutexLock -- * * This procedure is invoked to lock a mutex. This is a self initializing * mutex that is automatically finalized during Tcl_Finalize. * * Results: * None. * * Side effects: * May block the current thread. The mutex is aquired when this returns. * *---------------------------------------------------------------------- */ void Tcl_MutexLock( Tcl_Mutex *mutexPtr) /* The lock */ { CRITICAL_SECTION *csPtr; if (*mutexPtr == NULL) { TclpMasterLock(); /* * Double inside master lock check to avoid a race. */ if (*mutexPtr == NULL) { csPtr = ckalloc(sizeof(CRITICAL_SECTION)); InitializeCriticalSection(csPtr); *mutexPtr = (Tcl_Mutex)csPtr; TclRememberMutex(mutexPtr); } TclpMasterUnlock(); } csPtr = *((CRITICAL_SECTION **)mutexPtr); EnterCriticalSection(csPtr); } /* *---------------------------------------------------------------------- * * Tcl_MutexUnlock -- * * This procedure is invoked to unlock a mutex. * * Results: * None. * * Side effects: * The mutex is released when this returns. * *---------------------------------------------------------------------- */ void Tcl_MutexUnlock( Tcl_Mutex *mutexPtr) /* The lock */ { CRITICAL_SECTION *csPtr = *((CRITICAL_SECTION **)mutexPtr); LeaveCriticalSection(csPtr); } /* *---------------------------------------------------------------------- * * TclpFinalizeMutex -- * * This procedure is invoked to clean up one mutex. This is only safe to * call at the end of time. * * Results: * None. * * Side effects: * The mutex list is deallocated. * *---------------------------------------------------------------------- */ void TclpFinalizeMutex( Tcl_Mutex *mutexPtr) { CRITICAL_SECTION *csPtr = *(CRITICAL_SECTION **)mutexPtr; if (csPtr != NULL) { DeleteCriticalSection(csPtr); ckfree(csPtr); *mutexPtr = NULL; } } /* *---------------------------------------------------------------------- * * Tcl_ConditionWait -- * * This procedure is invoked to wait on a condition variable. The mutex * is atomically released as part of the wait, and automatically grabbed * when the condition is signaled. * * The mutex must be held when this procedure is called. * * Results: * None. * * Side effects: * May block the current thread. The mutex is aquired when this returns. * Will allocate memory for a HANDLE and initialize this the first time * this Tcl_Condition is used. * *---------------------------------------------------------------------- */ void Tcl_ConditionWait( Tcl_Condition *condPtr, /* Really (WinCondition **) */ Tcl_Mutex *mutexPtr, /* Really (CRITICAL_SECTION **) */ const Tcl_Time *timePtr) /* Timeout on waiting period */ { WinCondition *winCondPtr; /* Per-condition queue head */ CRITICAL_SECTION *csPtr; /* Caller's Mutex, after casting */ DWORD wtime; /* Windows time value */ int timeout; /* True if we got a timeout */ int doExit = 0; /* True if we need to do exit setup */ ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey); /* * Self initialize the two parts of the condition. The per-condition and * per-thread parts need to be handled independently. */ if (tsdPtr->flags == WIN_THREAD_UNINIT) { TclpMasterLock(); /* * Create the per-thread event and queue pointers. */ if (tsdPtr->flags == WIN_THREAD_UNINIT) { tsdPtr->condEvent = CreateEvent(NULL, TRUE /* manual reset */, FALSE /* non signaled */, NULL); tsdPtr->nextPtr = NULL; tsdPtr->prevPtr = NULL; tsdPtr->flags = WIN_THREAD_RUNNING; doExit = 1; } TclpMasterUnlock(); if (doExit) { /* * Create a per-thread exit handler to clean up the condEvent. We * must be careful to do this outside the Master Lock because * Tcl_CreateThreadExitHandler uses its own ThreadSpecificData, * and initializing that may drop back into the Master Lock. */ Tcl_CreateThreadExitHandler(FinalizeConditionEvent, tsdPtr); } } if (*condPtr == NULL) { TclpMasterLock(); /* * Initialize the per-condition queue pointers and Mutex. */ if (*condPtr == NULL) { winCondPtr = ckalloc(sizeof(WinCondition)); InitializeCriticalSection(&winCondPtr->condLock); winCondPtr->firstPtr = NULL; winCondPtr->lastPtr = NULL; *condPtr = (Tcl_Condition) winCondPtr; TclRememberCondition(condPtr); } TclpMasterUnlock(); } csPtr = *((CRITICAL_SECTION **)mutexPtr); winCondPtr = *((WinCondition **)condPtr); if (timePtr == NULL) { wtime = INFINITE; } else { wtime = timePtr->sec * 1000 + timePtr->usec / 1000; } /* * Queue the thread on the condition, using the per-condition lock for * serialization. */ tsdPtr->flags = WIN_THREAD_BLOCKED; tsdPtr->nextPtr = NULL; EnterCriticalSection(&winCondPtr->condLock); tsdPtr->prevPtr = winCondPtr->lastPtr; /* A: */ winCondPtr->lastPtr = tsdPtr; if (tsdPtr->prevPtr != NULL) { tsdPtr->prevPtr->nextPtr = tsdPtr; } if (winCondPtr->firstPtr == NULL) { winCondPtr->firstPtr = tsdPtr; } /* * Unlock the caller's mutex and wait for the condition, or a timeout. * There is a minor issue here in that we don't count down the timeout if * we get notified, but another thread grabs the condition before we do. * In that race condition we'll wait again for the full timeout. Timed * waits are dubious anyway. Either you have the locking protocol wrong * and are masking a deadlock, or you are using conditions to pause your * thread. */ LeaveCriticalSection(csPtr); timeout = 0; while (!timeout && (tsdPtr->flags & WIN_THREAD_BLOCKED)) { ResetEvent(tsdPtr->condEvent); LeaveCriticalSection(&winCondPtr->condLock); if (WaitForSingleObjectEx(tsdPtr->condEvent, wtime, TRUE) == WAIT_TIMEOUT) { timeout = 1; } EnterCriticalSection(&winCondPtr->condLock); } /* * Be careful on timeouts because the signal might arrive right around the * time limit and someone else could have taken us off the queue. */ if (timeout) { if (tsdPtr->flags & WIN_THREAD_RUNNING) { timeout = 0; } else { /* * When dequeuing, we can leave the tsdPtr->nextPtr and * tsdPtr->prevPtr with dangling pointers because they are * reinitialilzed w/out reading them when the thread is enqueued * later. */ if (winCondPtr->firstPtr == tsdPtr) { winCondPtr->firstPtr = tsdPtr->nextPtr; } else { tsdPtr->prevPtr->nextPtr = tsdPtr->nextPtr; } if (winCondPtr->lastPtr == tsdPtr) { winCondPtr->lastPtr = tsdPtr->prevPtr; } else { tsdPtr->nextPtr->prevPtr = tsdPtr->prevPtr; } tsdPtr->flags = WIN_THREAD_RUNNING; } } LeaveCriticalSection(&winCondPtr->condLock); EnterCriticalSection(csPtr); } /* *---------------------------------------------------------------------- * * Tcl_ConditionNotify -- * * This procedure is invoked to signal a condition variable. * * The mutex must be held during this call to avoid races, but this * interface does not enforce that. * * Results: * None. * * Side effects: * May unblock another thread. * *---------------------------------------------------------------------- */ void Tcl_ConditionNotify( Tcl_Condition *condPtr) { WinCondition *winCondPtr; ThreadSpecificData *tsdPtr; if (*condPtr != NULL) { winCondPtr = *((WinCondition **)condPtr); if (winCondPtr == NULL) { return; } /* * Loop through all the threads waiting on the condition and notify * them (i.e., broadcast semantics). The queue manipulation is guarded * by the per-condition coordinating mutex. */ EnterCriticalSection(&winCondPtr->condLock); while (winCondPtr->firstPtr != NULL) { tsdPtr = winCondPtr->firstPtr; winCondPtr->firstPtr = tsdPtr->nextPtr; if (winCondPtr->lastPtr == tsdPtr) { winCondPtr->lastPtr = NULL; } tsdPtr->flags = WIN_THREAD_RUNNING; tsdPtr->nextPtr = NULL; tsdPtr->prevPtr = NULL; /* Not strictly necessary, see A: */ SetEvent(tsdPtr->condEvent); } LeaveCriticalSection(&winCondPtr->condLock); } else { /* * No-one has used the condition variable, so there are no waiters. */ } } /* *---------------------------------------------------------------------- * * FinalizeConditionEvent -- * * This procedure is invoked to clean up the per-thread event used to * implement condition waiting. This is only safe to call at the end of * time. * * Results: * None. * * Side effects: * The per-thread event is closed. * *---------------------------------------------------------------------- */ static void FinalizeConditionEvent( ClientData data) { ThreadSpecificData *tsdPtr = (ThreadSpecificData *) data; tsdPtr->flags = WIN_THREAD_UNINIT; CloseHandle(tsdPtr->condEvent); } /* *---------------------------------------------------------------------- * * TclpFinalizeCondition -- * * This procedure is invoked to clean up a condition variable. This is * only safe to call at the end of time. * * This assumes the Master Lock is held. * * Results: * None. * * Side effects: * The condition variable is deallocated. * *---------------------------------------------------------------------- */ void TclpFinalizeCondition( Tcl_Condition *condPtr) { WinCondition *winCondPtr = *(WinCondition **)condPtr; /* * Note - this is called long after the thread-local storage is reclaimed. * The per-thread condition waiting event is reclaimed earlier in a * per-thread exit handler, which is called before thread local storage is * reclaimed. */ if (winCondPtr != NULL) { DeleteCriticalSection(&winCondPtr->condLock); ckfree(winCondPtr); *condPtr = NULL; } } /* * Additions by AOL for specialized thread memory allocator. */ #ifdef USE_THREAD_ALLOC Tcl_Mutex * TclpNewAllocMutex(void) { allocMutex *lockPtr; lockPtr = malloc(sizeof(allocMutex)); if (lockPtr == NULL) { Tcl_Panic("could not allocate lock"); } lockPtr->tlock = (Tcl_Mutex) &lockPtr->wlock; InitializeCriticalSection(&lockPtr->wlock); return &lockPtr->tlock; } void TclpFreeAllocMutex( Tcl_Mutex *mutex) /* The alloc mutex to free. */ { allocMutex *lockPtr = (allocMutex *) mutex; if (!lockPtr) { return; } DeleteCriticalSection(&lockPtr->wlock); free(lockPtr); } void TclpInitAllocCache(void) { /* * We need to make sure that TclpFreeAllocCache is called on each * thread that calls this, but only on threads that call this. */ tlsKey = TlsAlloc(); if (tlsKey == TLS_OUT_OF_INDEXES) { Tcl_Panic("could not allocate thread local storage"); } } void * TclpGetAllocCache(void) { void *result; result = TlsGetValue(tlsKey); if ((result == NULL) && (GetLastError() != NO_ERROR)) { Tcl_Panic("TlsGetValue failed from TclpGetAllocCache"); } return result; } void TclpSetAllocCache( void *ptr) { BOOL success; success = TlsSetValue(tlsKey, ptr); if (!success) { Tcl_Panic("TlsSetValue failed from TclpSetAllocCache"); } } void TclpFreeAllocCache( void *ptr) { BOOL success; if (ptr != NULL) { /* * Called by TclFinalizeThreadAlloc() and * TclFinalizeThreadAllocThread() during Tcl_Finalize() or * Tcl_FinalizeThread(). This function destroys the tsd key which * stores allocator caches in thread local storage. */ TclFreeAllocCache(ptr); success = TlsSetValue(tlsKey, NULL); if (!success) { Tcl_Panic("TlsSetValue failed from TclpFreeAllocCache"); } } else { /* * Called by us in TclFinalizeThreadAlloc() during the library * finalization initiated from Tcl_Finalize() */ success = TlsFree(tlsKey); if (!success) { Tcl_Panic("TlsFree failed from TclpFreeAllocCache"); } } } #endif /* USE_THREAD_ALLOC */ void * TclpThreadCreateKey(void) { DWORD *key; key = TclpSysAlloc(sizeof *key, 0); if (key == NULL) { Tcl_Panic("unable to allocate thread key!"); } *key = TlsAlloc(); if (*key == TLS_OUT_OF_INDEXES) { Tcl_Panic("unable to allocate thread-local storage"); } return key; } void TclpThreadDeleteKey( void *keyPtr) { DWORD *key = keyPtr; if (!TlsFree(*key)) { Tcl_Panic("unable to delete key"); } TclpSysFree(keyPtr); } void TclpThreadSetMasterTSD( void *tsdKeyPtr, void *ptr) { DWORD *key = tsdKeyPtr; if (!TlsSetValue(*key, ptr)) { Tcl_Panic("unable to set master TSD value"); } } void * TclpThreadGetMasterTSD( void *tsdKeyPtr) { DWORD *key = tsdKeyPtr; return TlsGetValue(*key); } #endif /* TCL_THREADS */ /* * Local Variables: * mode: c * c-basic-offset: 4 * fill-column: 78 * End: */