Apply simplification suggested by Chris: why assign() when operator = will do?

[oota-llvm.git] / lib / Support / Signals.cpp

diff --git a/lib/Support/Signals.cpp b/lib/Support/Signals.cpp
index 29daedf0fb9a05a3ead305ba4566a725ecc3113a..112cd783e436ced3fa6123c69f7031c8c58ac68d 100644 (file)
--- a/lib/Support/Signals.cpp
+++ b/lib/Support/Signals.cpp
@@ -1,7 +1,14 @@
 //===- Signals.cpp - Signal Handling support ------------------------------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
 //
 // This file defines some helpful functions for dealing with the possibility of
-// unix signals occuring while your program is running.
+// Unix signals occuring while your program is running.
 //
 //===----------------------------------------------------------------------===//
 
@@ -10,10 +17,17 @@
 #include <algorithm>
 #include <cstdlib>
 #include <cstdio>
+#include "Config/config.h"     // Get the signal handler return type
+#ifdef HAVE_EXECINFO_H
+# include <execinfo.h>         // For backtrace().
+#endif
 #include <signal.h>
-using std::string;
+#include <unistd.h>
+#include <sys/wait.h>
+#include <cerrno>
+using namespace llvm;
 
-static std::vector<string> FilesToRemove;
+static std::vector<std::string> FilesToRemove;
 
 // IntSigs - Signals that may interrupt the program at any time.
 static const int IntSigs[] = {
@@ -24,14 +38,75 @@ static const int *IntSigsEnd = IntSigs + sizeof(IntSigs)/sizeof(IntSigs[0]);
 // KillSigs - Signals that are synchronous with the program that will cause it
 // to die.
 static const int KillSigs[] = {
-  SIGILL, SIGTRAP, SIGABRT, SIGEMT, SIGFPE,
-  SIGBUS, SIGSEGV, SIGSYS, SIGXCPU, SIGXFSZ
+  SIGILL, SIGTRAP, SIGABRT, SIGFPE, SIGBUS, SIGSEGV, SIGSYS, SIGXCPU, SIGXFSZ
+#ifdef SIGEMT
+  , SIGEMT
+#endif
 };
 static const int *KillSigsEnd = KillSigs + sizeof(KillSigs)/sizeof(KillSigs[0]);
 
+#ifdef HAVE_BACKTRACE
+static void* StackTrace[256];
+#endif
+
+
+// PrintStackTrace - In the case of a program crash or fault, print out a stack
+// trace so that the user has an indication of why and where we died.
+//
+// On glibc systems we have the 'backtrace' function, which works nicely, but
+// doesn't demangle symbols.  In order to backtrace symbols, we fork and exec a
+// 'c++filt' process to do the demangling.  This seems like the simplest and
+// most robust solution when we can't allocate memory (such as in a signal
+// handler).  If we can't find 'c++filt', we fallback to printing mangled names.
+//
+static void PrintStackTrace() {
+#ifdef HAVE_BACKTRACE
+  // Use backtrace() to output a backtrace on Linux systems with glibc.
+  int depth = backtrace(StackTrace, sizeof(StackTrace)/sizeof(StackTrace[0]));
+  
+  // Create a one-way unix pipe.  The backtracing process writes to PipeFDs[1],
+  // the c++filt process reads from PipeFDs[0].
+  int PipeFDs[2];
+  if (pipe(PipeFDs)) {
+    backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
+    return;
+  }
+
+  switch (pid_t ChildPID = fork()) {
+  case -1:        // Error forking, print mangled stack trace
+    close(PipeFDs[0]);
+    close(PipeFDs[1]);
+    backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
+    return;
+  default:        // backtracing process
+    close(PipeFDs[0]);  // Close the reader side.
+
+    // Print the mangled backtrace into the pipe.
+    backtrace_symbols_fd(StackTrace, depth, PipeFDs[1]);
+    close(PipeFDs[1]);   // We are done writing.
+    while (waitpid(ChildPID, 0, 0) == -1)
+      if (errno != EINTR) break;
+    return;
+
+  case 0:         // c++filt process
+    close(PipeFDs[1]);    // Close the writer side.
+    dup2(PipeFDs[0], 0);  // Read from standard input
+    close(PipeFDs[0]);    // Close the old descriptor
+    dup2(2, 1);           // Revector stdout -> stderr
+
+    // Try to run c++filt or gc++filt.  If neither is found, call back on 'cat'
+    // to print the mangled stack trace.  If we can't find cat, just exit.
+    execlp("c++filt", "c++filt", 0);
+    execlp("gc++filt", "gc++filt", 0);
+    execlp("cat", "cat", 0);
+    execlp("/bin/cat", "cat", 0);
+    exit(0);
+  }
+#endif
+}
 
 // SignalHandler - The signal handler that runs...
-static void SignalHandler(int Sig) {
+static RETSIGTYPE SignalHandler(int Sig) {
   while (!FilesToRemove.empty()) {
     std::remove(FilesToRemove.back().c_str());
     FilesToRemove.pop_back();
@@ -40,15 +115,24 @@ static void SignalHandler(int Sig) {
   if (std::find(IntSigs, IntSigsEnd, Sig) != IntSigsEnd)
     exit(1);   // If this is an interrupt signal, exit the program
 
-  // Otherwise if it is a fault (like SEGV) reissue the signal to die...
+  // Otherwise if it is a fault (like SEGV) output the stacktrace to
+  // STDERR (if we can) and reissue the signal to die...
+  PrintStackTrace();
+  signal(Sig, SIG_DFL);
 }
 
 static void RegisterHandler(int Signal) { signal(Signal, SignalHandler); }
 
 // RemoveFileOnSignal - The public API
-void RemoveFileOnSignal(const string &Filename) {
+void llvm::RemoveFileOnSignal(const std::string &Filename) {
   FilesToRemove.push_back(Filename);
 
   std::for_each(IntSigs, IntSigsEnd, RegisterHandler);
   std::for_each(KillSigs, KillSigsEnd, RegisterHandler);
 }
+
+/// PrintStackTraceOnErrorSignal - When an error signal (such as SIBABRT or
+/// SIGSEGV) is delivered to the process, print a stack trace and then exit.
+void llvm::PrintStackTraceOnErrorSignal() {
+  std::for_each(KillSigs, KillSigsEnd, RegisterHandler);
+}