Signals.cpp revision b9632bee7ca842c2721340c42e18bfd0109ce5aa
1//===- Signals.cpp - Signal Handling support ------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines some helpful functions for dealing with the possibility of 11// Unix signals occuring while your program is running. 12// 13//===----------------------------------------------------------------------===// 14 15#include "Support/Signals.h" 16#include <vector> 17#include <algorithm> 18#include <cstdlib> 19#include <cstdio> 20#include "Config/config.h" // Get the signal handler return type 21#ifdef HAVE_EXECINFO_H 22# include <execinfo.h> // For backtrace(). 23#endif 24#include <signal.h> 25#include <unistd.h> 26#include <sys/wait.h> 27#include <cerrno> 28using namespace llvm; 29 30static std::vector<std::string> FilesToRemove; 31 32// IntSigs - Signals that may interrupt the program at any time. 33static const int IntSigs[] = { 34 SIGHUP, SIGINT, SIGQUIT, SIGKILL, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2 35}; 36static const int *IntSigsEnd = IntSigs + sizeof(IntSigs)/sizeof(IntSigs[0]); 37 38// KillSigs - Signals that are synchronous with the program that will cause it 39// to die. 40static const int KillSigs[] = { 41 SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV, SIGSYS, SIGXCPU, SIGXFSZ 42#ifdef SIGEMT 43 , SIGEMT 44#endif 45}; 46static const int *KillSigsEnd = KillSigs + sizeof(KillSigs)/sizeof(KillSigs[0]); 47 48#ifdef HAVE_BACKTRACE 49static void* StackTrace[256]; 50#endif 51 52 53// PrintStackTrace - In the case of a program crash or fault, print out a stack 54// trace so that the user has an indication of why and where we died. 55// 56// On glibc systems we have the 'backtrace' function, which works nicely, but 57// doesn't demangle symbols. In order to backtrace symbols, we fork and exec a 58// 'c++filt' process to do the demangling. This seems like the simplest and 59// most robust solution when we can't allocate memory (such as in a signal 60// handler). If we can't find 'c++filt', we fallback to printing mangled names. 61// 62static void PrintStackTrace() { 63#ifdef HAVE_BACKTRACE 64 // Use backtrace() to output a backtrace on Linux systems with glibc. 65 int depth = backtrace(StackTrace, sizeof(StackTrace)/sizeof(StackTrace[0])); 66 67 // Create a one-way unix pipe. The backtracing process writes to PipeFDs[1], 68 // the c++filt process reads from PipeFDs[0]. 69 int PipeFDs[2]; 70 if (pipe(PipeFDs)) { 71 backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO); 72 return; 73 } 74 75 switch (pid_t ChildPID = fork()) { 76 case -1: // Error forking, print mangled stack trace 77 close(PipeFDs[0]); 78 close(PipeFDs[1]); 79 backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO); 80 return; 81 default: // backtracing process 82 close(PipeFDs[0]); // Close the reader side. 83 84 // Print the mangled backtrace into the pipe. 85 backtrace_symbols_fd(StackTrace, depth, PipeFDs[1]); 86 close(PipeFDs[1]); // We are done writing. 87 while (waitpid(ChildPID, 0, 0) == -1) 88 if (errno != EINTR) break; 89 return; 90 91 case 0: // c++filt process 92 close(PipeFDs[1]); // Close the writer side. 93 dup2(PipeFDs[0], 0); // Read from standard input 94 close(PipeFDs[0]); // Close the old descriptor 95 dup2(2, 1); // Revector stdout -> stderr 96 97 // Try to run c++filt or gc++filt. If neither is found, call back on 'cat' 98 // to print the mangled stack trace. If we can't find cat, just exit. 99 execlp("c++filt", "c++filt", 0); 100 execlp("gc++filt", "gc++filt", 0); 101 execlp("cat", "cat", 0); 102 execlp("/usr/bin/cat", "cat", 0); 103 exit(0); 104 } 105#endif 106} 107 108// SignalHandler - The signal handler that runs... 109static RETSIGTYPE SignalHandler(int Sig) { 110 while (!FilesToRemove.empty()) { 111 std::remove(FilesToRemove.back().c_str()); 112 FilesToRemove.pop_back(); 113 } 114 115 if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd) 116 exit(1); // If this is an interrupt signal, exit the program 117 118 // Otherwise if it is a fault (like SEGV) output the stacktrace to 119 // STDERR (if we can) and reissue the signal to die... 120 PrintStackTrace(); 121 signal(Sig, SIG_DFL); 122} 123 124static void RegisterHandler(int Signal) { signal(Signal, SignalHandler); } 125 126// RemoveFileOnSignal - The public API 127void llvm::RemoveFileOnSignal(const std::string &Filename) { 128 FilesToRemove.push_back(Filename); 129 130 std::for_each(IntSigs, IntSigsEnd, RegisterHandler); 131 std::for_each(KillSigs, KillSigsEnd, RegisterHandler); 132} 133 134/// PrintStackTraceOnErrorSignal - When an error signal (such as SIBABRT or 135/// SIGSEGV) is delivered to the process, print a stack trace and then exit. 136void llvm::PrintStackTraceOnErrorSignal() { 137 std::for_each(KillSigs, KillSigsEnd, RegisterHandler); 138} 139