1 //===- Signals.cpp - Generic Unix Signals Implementation -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines some helpful functions for dealing with the possibility of
11 // Unix signals occurring while your program is running.
13 //===----------------------------------------------------------------------===//
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/Support/Mutex.h"
22 # include <execinfo.h> // For backtrace().
37 #include <mach/mach.h>
42 static RETSIGTYPE SignalHandler(int Sig); // defined below.
44 static SmartMutex<true> SignalsMutex;
46 /// InterruptFunction - The function to call if ctrl-c is pressed.
47 static void (*InterruptFunction)() = nullptr;
49 static std::vector<std::string> FilesToRemove;
50 static std::vector<std::pair<void(*)(void*), void*> > CallBacksToRun;
52 // IntSigs - Signals that represent requested termination. There's no bug
53 // or failure, or if there is, it's not our direct responsibility. For whatever
54 // reason, our continued execution is no longer desirable.
55 static const int IntSigs[] = {
56 SIGHUP, SIGINT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
58 static const int *const IntSigsEnd = std::end(IntSigs);
60 // KillSigs - Signals that represent that we have a bug, and our prompt
61 // termination has been ordered.
62 static const int KillSigs[] = {
63 SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV, SIGQUIT
77 static const int *const KillSigsEnd = std::end(KillSigs);
79 static unsigned NumRegisteredSignals = 0;
83 } RegisteredSignalInfo[(sizeof(IntSigs)+sizeof(KillSigs))/sizeof(KillSigs[0])];
86 static void RegisterHandler(int Signal) {
87 assert(NumRegisteredSignals <
88 sizeof(RegisteredSignalInfo)/sizeof(RegisteredSignalInfo[0]) &&
89 "Out of space for signal handlers!");
91 struct sigaction NewHandler;
93 NewHandler.sa_handler = SignalHandler;
94 NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND;
95 sigemptyset(&NewHandler.sa_mask);
97 // Install the new handler, save the old one in RegisteredSignalInfo.
98 sigaction(Signal, &NewHandler,
99 &RegisteredSignalInfo[NumRegisteredSignals].SA);
100 RegisteredSignalInfo[NumRegisteredSignals].SigNo = Signal;
101 ++NumRegisteredSignals;
104 static void RegisterHandlers() {
105 // If the handlers are already registered, we're done.
106 if (NumRegisteredSignals != 0) return;
108 std::for_each(IntSigs, IntSigsEnd, RegisterHandler);
109 std::for_each(KillSigs, KillSigsEnd, RegisterHandler);
112 static void UnregisterHandlers() {
113 // Restore all of the signal handlers to how they were before we showed up.
114 for (unsigned i = 0, e = NumRegisteredSignals; i != e; ++i)
115 sigaction(RegisteredSignalInfo[i].SigNo,
116 &RegisteredSignalInfo[i].SA, nullptr);
117 NumRegisteredSignals = 0;
121 /// RemoveFilesToRemove - Process the FilesToRemove list. This function
122 /// should be called with the SignalsMutex lock held.
123 /// NB: This must be an async signal safe function. It cannot allocate or free
124 /// memory, even in debug builds.
125 static void RemoveFilesToRemove() {
126 // We avoid iterators in case of debug iterators that allocate or release
128 for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i) {
129 // We rely on a std::string implementation for which repeated calls to
130 // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
131 // strings to try to ensure this is safe.
132 const char *path = FilesToRemove[i].c_str();
134 // Get the status so we can determine if it's a file or directory. If we
135 // can't stat the file, ignore it.
137 if (stat(path, &buf) != 0)
140 // If this is not a regular file, ignore it. We want to prevent removal of
141 // special files like /dev/null, even if the compiler is being run with the
142 // super-user permissions.
143 if (!S_ISREG(buf.st_mode))
146 // Otherwise, remove the file. We ignore any errors here as there is nothing
152 // SignalHandler - The signal handler that runs.
153 static RETSIGTYPE SignalHandler(int Sig) {
154 // Restore the signal behavior to default, so that the program actually
155 // crashes when we return and the signal reissues. This also ensures that if
156 // we crash in our signal handler that the program will terminate immediately
157 // instead of recursing in the signal handler.
158 UnregisterHandlers();
160 // Unmask all potentially blocked kill signals.
162 sigfillset(&SigMask);
163 sigprocmask(SIG_UNBLOCK, &SigMask, nullptr);
165 SignalsMutex.acquire();
166 RemoveFilesToRemove();
168 if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) {
169 if (InterruptFunction) {
170 void (*IF)() = InterruptFunction;
171 SignalsMutex.release();
172 InterruptFunction = nullptr;
173 IF(); // run the interrupt function.
177 SignalsMutex.release();
178 raise(Sig); // Execute the default handler.
182 SignalsMutex.release();
184 // Otherwise if it is a fault (like SEGV) run any handler.
185 for (unsigned i = 0, e = CallBacksToRun.size(); i != e; ++i)
186 CallBacksToRun[i].first(CallBacksToRun[i].second);
189 // On S/390, certain signals are delivered with PSW Address pointing to
190 // *after* the faulting instruction. Simply returning from the signal
191 // handler would continue execution after that point, instead of
192 // re-raising the signal. Raise the signal manually in those cases.
193 if (Sig == SIGILL || Sig == SIGFPE || Sig == SIGTRAP)
198 void llvm::sys::RunInterruptHandlers() {
199 sys::SmartScopedLock<true> Guard(SignalsMutex);
200 RemoveFilesToRemove();
203 void llvm::sys::SetInterruptFunction(void (*IF)()) {
205 sys::SmartScopedLock<true> Guard(SignalsMutex);
206 InterruptFunction = IF;
211 // RemoveFileOnSignal - The public API
212 bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
213 std::string* ErrMsg) {
215 sys::SmartScopedLock<true> Guard(SignalsMutex);
216 std::string *OldPtr = FilesToRemove.empty() ? nullptr : &FilesToRemove[0];
217 FilesToRemove.push_back(Filename);
219 // We want to call 'c_str()' on every std::string in this vector so that if
220 // the underlying implementation requires a re-allocation, it happens here
221 // rather than inside of the signal handler. If we see the vector grow, we
222 // have to call it on every entry. If it remains in place, we only need to
223 // call it on the latest one.
224 if (OldPtr == &FilesToRemove[0])
225 FilesToRemove.back().c_str();
227 for (unsigned i = 0, e = FilesToRemove.size(); i != e; ++i)
228 FilesToRemove[i].c_str();
235 // DontRemoveFileOnSignal - The public API
236 void llvm::sys::DontRemoveFileOnSignal(StringRef Filename) {
237 sys::SmartScopedLock<true> Guard(SignalsMutex);
238 std::vector<std::string>::reverse_iterator RI =
239 std::find(FilesToRemove.rbegin(), FilesToRemove.rend(), Filename);
240 std::vector<std::string>::iterator I = FilesToRemove.end();
241 if (RI != FilesToRemove.rend())
242 I = FilesToRemove.erase(RI.base()-1);
244 // We need to call c_str() on every element which would have been moved by
245 // the erase. These elements, in a C++98 implementation where c_str()
246 // requires a reallocation on the first call may have had the call to c_str()
247 // made on insertion become invalid by being copied down an element.
248 for (std::vector<std::string>::iterator E = FilesToRemove.end(); I != E; ++I)
252 /// AddSignalHandler - Add a function to be called when a signal is delivered
253 /// to the process. The handler can have a cookie passed to it to identify
254 /// what instance of the handler it is.
255 void llvm::sys::AddSignalHandler(void (*FnPtr)(void *), void *Cookie) {
256 CallBacksToRun.push_back(std::make_pair(FnPtr, Cookie));
261 // PrintStackTrace - In the case of a program crash or fault, print out a stack
262 // trace so that the user has an indication of why and where we died.
264 // On glibc systems we have the 'backtrace' function, which works nicely, but
265 // doesn't demangle symbols.
266 void llvm::sys::PrintStackTrace(FILE *FD) {
267 #if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
268 static void* StackTrace[256];
269 // Use backtrace() to output a backtrace on Linux systems with glibc.
270 int depth = backtrace(StackTrace,
271 static_cast<int>(array_lengthof(StackTrace)));
272 #if HAVE_DLFCN_H && __GNUG__
274 for (int i = 0; i < depth; ++i) {
276 dladdr(StackTrace[i], &dlinfo);
277 const char* name = strrchr(dlinfo.dli_fname, '/');
280 if (!name) nwidth = strlen(dlinfo.dli_fname);
281 else nwidth = strlen(name) - 1;
283 if (nwidth > width) width = nwidth;
286 for (int i = 0; i < depth; ++i) {
288 dladdr(StackTrace[i], &dlinfo);
290 fprintf(FD, "%-2d", i);
292 const char* name = strrchr(dlinfo.dli_fname, '/');
293 if (!name) fprintf(FD, " %-*s", width, dlinfo.dli_fname);
294 else fprintf(FD, " %-*s", width, name+1);
296 fprintf(FD, " %#0*lx",
297 (int)(sizeof(void*) * 2) + 2, (unsigned long)StackTrace[i]);
299 if (dlinfo.dli_sname != nullptr) {
303 char* d = abi::__cxa_demangle(dlinfo.dli_sname, nullptr, nullptr, &res);
307 if (!d) fputs(dlinfo.dli_sname, FD);
311 // FIXME: When we move to C++11, use %t length modifier. It's not in
312 // C++03 and causes gcc to issue warnings. Losing the upper 32 bits of
313 // the stack offset for a stack dump isn't likely to cause any problems.
314 fprintf(FD, " + %u",(unsigned)((char*)StackTrace[i]-
315 (char*)dlinfo.dli_saddr));
320 backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
325 static void PrintStackTraceSignalHandler(void *) {
326 PrintStackTrace(stderr);
329 /// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
330 /// SIGSEGV) is delivered to the process, print a stack trace and then exit.
331 void llvm::sys::PrintStackTraceOnErrorSignal() {
332 AddSignalHandler(PrintStackTraceSignalHandler, nullptr);
334 #if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
335 // Environment variable to disable any kind of crash dialog.
336 if (getenv("LLVM_DISABLE_CRASH_REPORT")) {
337 mach_port_t self = mach_task_self();
339 exception_mask_t mask = EXC_MASK_CRASH;
341 kern_return_t ret = task_set_exception_ports(self,
344 EXCEPTION_STATE_IDENTITY | MACH_EXCEPTION_CODES,
354 // On Darwin, raise sends a signal to the main thread instead of the current
355 // thread. This has the unfortunate effect that assert() and abort() will end up
356 // bypassing our crash recovery attempts. We work around this for anything in
357 // the same linkage unit by just defining our own versions of the assert handler
360 #if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
366 return pthread_kill(pthread_self(), sig);
369 void __assert_rtn(const char *func,
374 fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
375 expr, func, file, line);
377 fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",