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27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29 #include "utils/signals/programmer.hpp"
30
31 extern "C" {
32 #include <signal.h>
33 }
34
35 #include <cerrno>
36
37 #include "utils/format/macros.hpp"
38 #include "utils/logging/macros.hpp"
39 #include "utils/sanity.hpp"
40 #include "utils/signals/exceptions.hpp"
41
42
43 namespace utils {
44 namespace signals {
45
46
47 /// Internal implementation for the signals::programmer class.
48 struct programmer::impl {
49 /// The number of the signal managed by this programmer.
50 int signo;
51
52 /// Whether the signal is currently programmed by us or not.
53 bool programmed;
54
55 /// The signal handler that we replaced; to be restored on unprogramming.
56 struct ::sigaction old_sa;
57
58 /// Initializes the internal implementation of the programmer.
59 ///
60 /// \param signo_ The signal number.
implutils::signals::programmer::impl61 impl(const int signo_) :
62 signo(signo_),
63 programmed(false)
64 {
65 }
66 };
67
68
69 } // namespace signals
70 } // namespace utils
71
72
73 namespace signals = utils::signals;
74
75
76 /// Programs a signal handler.
77 ///
78 /// \param signo The signal for which to install the handler.
79 /// \param handler The handler to install.
80 ///
81 /// \throw signals::system_error If there is an error programming the signal.
programmer(const int signo,const handler_type handler)82 signals::programmer::programmer(const int signo, const handler_type handler) :
83 _pimpl(new impl(signo))
84 {
85 struct ::sigaction sa;
86 sa.sa_handler = handler;
87 sigemptyset(&sa.sa_mask);
88 sa.sa_flags = SA_RESTART;
89
90 if (::sigaction(_pimpl->signo, &sa, &_pimpl->old_sa) == -1) {
91 const int original_errno = errno;
92 throw system_error(F("Could not install handler for signal %s") %
93 _pimpl->signo, original_errno);
94 } else
95 _pimpl->programmed = true;
96 }
97
98
99 /// Destructor; unprograms the signal handler if still programmed.
100 ///
101 /// Given that this is a destructor and it can't report errors back to the
102 /// caller, the caller must attempt to call unprogram() on its own.
~programmer(void)103 signals::programmer::~programmer(void)
104 {
105 if (_pimpl->programmed) {
106 LW("Destroying still-programmed signals::programmer object");
107 try {
108 unprogram();
109 } catch (const system_error& e) {
110 UNREACHABLE;
111 }
112 }
113 }
114
115
116 /// Unprograms the signal handler.
117 ///
118 /// \pre The signal handler is programmed (i.e. this can only be called once).
119 ///
120 /// \throw system_error If unprogramming the signal failed. If this happens,
121 /// the signal is left programmed, this object forgets about the signal and
122 /// therefore there is no way to restore the original handler.
123 void
unprogram(void)124 signals::programmer::unprogram(void)
125 {
126 PRE(_pimpl->programmed);
127
128 // If we fail, we don't want the destructor to attempt to unprogram the
129 // handler again, as it would result in a crash.
130 _pimpl->programmed = false;
131
132 if (::sigaction(_pimpl->signo, &_pimpl->old_sa, NULL) == -1) {
133 const int original_errno = errno;
134 throw system_error(F("Could not reset handler for signal %s") %
135 _pimpl->signo, original_errno);
136 }
137 }
138