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modules/magick: Document and improve #89 solution.

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This commit is contained in:
Jason Volk 2019-08-25 13:54:05 -07:00
parent 3d445fd26c
commit 9a7f53e33c
1 changed files with 53 additions and 11 deletions
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64
modules/magick.cc
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@ -134,10 +134,29 @@ ircd::magick::version_abi
}
};
//
// Magick library signal handler workarounds.
//
// By default the graphicsmagick library installs signal handlers on
// supporting platforms starting in InitializeMagick() for the duration
// of the library. These handlers provide no essential functionality,
// polluting the address space for other libraries and users of our libircd,
// causing unexpected behavior.
//
// Even though the library makes a good faith attempt to not step on already-
// installed signal handlers: it falls short by not maintaining the full
// sigaction structure. It loses information for SA_SIGINFO handlers, etc.
//
// Our principal workaround involves interposing this function (thankfully
// exported by the library). Unfortunately this doesn't work in all
// environments so we retain a full list of signal numbers the libmagick
// interferes with.
namespace ircd::magick
{
extern const int sig_overrides[];
extern const size_t sig_overrides_num;
static void sig_pre(), sig_post();
}
decltype(ircd::magick::sig_overrides)
@ -164,6 +183,38 @@ ircd::magick::sig_overrides_num
sizeof(sig_overrides) / sizeof(int)
};
#ifdef HAVE_SIGNAL_H
static struct sigaction
ircd_magick_sig_vector[ircd::magick::sig_overrides_num];
#endif
void
ircd::magick::sig_pre()
{
#ifdef HAVE_SIGNAL_H
for(size_t i(0); i < sig_overrides_num; ++i)
syscall(::sigaction, sig_overrides[i], nullptr, ircd_magick_sig_vector + i);
#endif HAVE_SIGNAL_H
}
void
ircd::magick::sig_post()
{
#ifdef HAVE_SIGNAL_H
for(size_t i(0); i < sig_overrides_num; ++i)
syscall(::sigaction, sig_overrides[i], ircd_magick_sig_vector + i, nullptr);
#endif HAVE_SIGNAL_H
}
extern "C" void
InitializeMagickSignalHandlers(void)
{
ircd::log::debug
{
ircd::magick::log, "Bypassed InitializeMagickSignalHandlers()",
};
}
//
// init
//
@ -188,12 +239,7 @@ ircd::magick::init()
long(version_abi),
};
#ifdef HAVE_SIGNAL_H
struct sigaction sig_vector[sig_overrides_num];
for(size_t i(0); i < sig_overrides_num; ++i)
syscall(::sigaction, sig_overrides[i], nullptr, sig_vector + i);
#endif
sig_pre();
InitializeMagick(nullptr);
MagickAllocFunctions(handle_free, handle_malloc, handle_realloc);
SetFatalErrorHandler(handle_fatal);
@ -203,11 +249,7 @@ ircd::magick::init()
//SetLogEventMask("all"); // Pollutes stderr :/ can't fix
SetMonitorHandler(handle_progress);
SetMagickResourceLimit(ThreadsResource, 1UL);
#ifdef HAVE_SIGNAL_H
for(size_t i(0); i < sig_overrides_num; ++i)
syscall(::sigaction, sig_overrides[i], sig_vector + i, nullptr);
#endif
sig_post();
call_ready = true;
call_dock.notify_all();