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Failure Signal Handler

Stacktrace as Default Failure Handler

The library provides a convenient signal handler that will dump useful information when the program crashes on certain signals such as SIGSEGV. The signal handler can be installed by google::InstallFailureSignalHandler(). The following is an example of output from the signal handler.

*** Aborted at 1225095260 (unix time) try "date -d @1225095260" if you are using GNU date ***
*** SIGSEGV (@0x0) received by PID 17711 (TID 0x7f893090a6f0) from PID 0; stack trace: ***
PC: @           0x412eb1 TestWaitingLogSink::send()
    @     0x7f892fb417d0 (unknown)
    @           0x412eb1 TestWaitingLogSink::send()
    @     0x7f89304f7f06 google::LogMessage::SendToLog()
    @     0x7f89304f35af google::LogMessage::Flush()
    @     0x7f89304f3739 google::LogMessage::~LogMessage()
    @           0x408cf4 TestLogSinkWaitTillSent()
    @           0x4115de main
    @     0x7f892f7ef1c4 (unknown)
    @           0x4046f9 (unknown)

Customizing Handler Output

By default, the signal handler writes the failure dump to the standard error. However, it is possible to customize the destination by installing a callback using the google::InstallFailureWriter() function. The function expects a pointer to a function with the following signature:

void YourFailureWriter(const char* message/* (1)! */, std::size_t length/* (2)! */);

  1. The pointer references the start of the failure message.

    Danger

    The string is not null-terminated.

  2. The message length in characters.

Possible overflow errors

Users should not expect the message string to be null-terminated.

User-defined Failure Function

FATAL severity level messages or unsatisfied CHECK condition terminate your program. You can change the behavior of the termination by google::InstallFailureFunction.

void YourFailureFunction() {
  // Reports something...
  exit(EXIT_FAILURE);
}

int main(int argc, char* argv[]) {
  google::InstallFailureFunction(&YourFailureFunction);
}

By default, glog tries to dump the stacktrace and calls std::abort. The stacktrace is generated only when running the application on a system supported1 by glog.

  1. To extract the stack trace, glog currently supports the following targets:

    • x86, x86_64,
    • PowerPC architectures,
    • libunwind,
    • and the Debug Help Library (dbghelp) on Windows.

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