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It is not safe to call fork in PrintStackTrace. Sometimes it freezes the program.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47161 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -61,54 +61,12 @@ void* StackTrace[256];
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// trace so that the user has an indication of why and where we died.
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//
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// On glibc systems we have the 'backtrace' function, which works nicely, but
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// doesn't demangle symbols. In order to backtrace symbols, we fork and exec a
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// 'c++filt' process to do the demangling. This seems like the simplest and
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// most robust solution when we can't allocate memory (such as in a signal
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// handler). If we can't find 'c++filt', we fallback to printing mangled names.
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//
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// doesn't demangle symbols.
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void PrintStackTrace() {
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#ifdef HAVE_BACKTRACE
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// Use backtrace() to output a backtrace on Linux systems with glibc.
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int depth = backtrace(StackTrace, array_lengthof(StackTrace));
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// Create a one-way unix pipe. The backtracing process writes to PipeFDs[1],
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// the c++filt process reads from PipeFDs[0].
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int PipeFDs[2];
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if (pipe(PipeFDs)) {
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backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
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return;
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}
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switch (pid_t ChildPID = fork()) {
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case -1: // Error forking, print mangled stack trace
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close(PipeFDs[0]);
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close(PipeFDs[1]);
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backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
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return;
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default: // backtracing process
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close(PipeFDs[0]); // Close the reader side.
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// Print the mangled backtrace into the pipe.
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backtrace_symbols_fd(StackTrace, depth, PipeFDs[1]);
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close(PipeFDs[1]); // We are done writing.
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while (waitpid(ChildPID, 0, 0) == -1)
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if (errno != EINTR) break;
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return;
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case 0: // c++filt process
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close(PipeFDs[1]); // Close the writer side.
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dup2(PipeFDs[0], 0); // Read from standard input
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close(PipeFDs[0]); // Close the old descriptor
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dup2(2, 1); // Revector stdout -> stderr
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// Try to run c++filt or gc++filt. If neither is found, call back on 'cat'
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// to print the mangled stack trace. If we can't find cat, just exit.
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execlp("c++filt", "c++filt", (char*)NULL);
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execlp("gc++filt", "gc++filt", (char*)NULL);
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execlp("cat", "cat", (char*)NULL);
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execlp("/bin/cat", "cat", (char*)NULL);
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exit(0);
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}
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backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
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#endif
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}
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