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Diffstat (limited to 'indra/llcommon/tests/llexception_test.cpp')
| -rw-r--r-- | indra/llcommon/tests/llexception_test.cpp | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/indra/llcommon/tests/llexception_test.cpp b/indra/llcommon/tests/llexception_test.cpp new file mode 100644 index 0000000000..6bee1943c2 --- /dev/null +++ b/indra/llcommon/tests/llexception_test.cpp @@ -0,0 +1,308 @@ +/** + * @file llexception_test.cpp + * @author Nat Goodspeed + * @date 2016-08-12 + * @brief Tests for throwing exceptions. + * + * This isn't a regression test: it doesn't need to be run every build, which + * is why the corresponding line in llcommon/CMakeLists.txt is commented out. + * Rather it's a head-to-head test of what kind of exception information we + * can collect from various combinations of exception base classes, type of + * throw verb and sequences of catch clauses. + * + * This "test" makes no ensure() calls: its output goes to stdout for human + * examination. + * + * As of 2016-08-12 with Boost 1.57, we come to the following conclusions. + * These should probably be re-examined from time to time as we update Boost. + * + * - It is indisputably beneficial to use BOOST_THROW_EXCEPTION() rather than + * plain throw. The macro annotates the exception object with the filename, + * line number and function name from which the exception was thrown. + * + * - That being the case, deriving only from boost::exception isn't an option. + * Every exception object passed to BOOST_THROW_EXCEPTION() must be derived + * directly or indirectly from std::exception. The only question is whether + * to also derive from boost::exception. We decided to derive LLException + * from both, as it makes message output slightly cleaner, but this is a + * trivial reason: if a strong reason emerges to prefer single inheritance, + * dropping the boost::exception base class shouldn't be a problem. + * + * - (As you will have guessed, ridiculous things like a char* or int or a + * class derived from neither boost::exception nor std::exception can only + * be caught by that specific type or (...), and + * boost::current_exception_diagnostic_information() simply throws up its + * hands and confesses utter ignorance. Stay away from such nonsense.) + * + * - But if you derive from std::exception, to nat's surprise, + * boost::current_exception_diagnostic_information() gives as much + * information about exceptions in a catch (...) clause as you can get from + * a specific catch (const std::exception&) clause, notably the concrete + * exception class and the what() string. So instead of a sequence like + * + * try { ... } + * catch (const boost::exception& e) { ... boost-flavored logging ... } + * catch (const std::exception& e) { ... std::exception logging ... } + * catch (...) { ... generic logging ... } + * + * we should be able to get away with only a catch (...) clause that logs + * boost::current_exception_diagnostic_information(). + * + * - Going further: boost::current_exception_diagnostic_information() provides + * just as much information even within a std::set_terminate() handler. So + * it might not even be strictly necessary to include a catch (...) clause + * since the viewer does use std::set_terminate(). + * + * - (We might consider adding a catch (int) clause because Kakadu internally + * throws ints, and who knows if one of those might leak out. If it does, + * boost::current_exception_diagnostic_information() can do nothing with it. + * A catch (int) clause could at least log the value and rethrow.) + * + * $LicenseInfo:firstyear=2016&license=viewerlgpl$ + * Copyright (c) 2016, Linden Research, Inc. + * $/LicenseInfo$ + */ + +// Precompiled header +#include "linden_common.h" +// associated header +#include "llexception.h" +// STL headers +// std headers +#include <typeinfo> +// external library headers +#include <boost/throw_exception.hpp> +// other Linden headers +#include "../test/lltut.h" + +// helper for display output +// usage: std::cout << center(some string value, fill char, width) << std::endl; +// (assumes it's the only thing on that particular line) +struct center +{ + center(const std::string& label, char fill, std::size_t width): + mLabel(label), + mFill(fill), + mWidth(width) + {} + + // Use friend declaration not because we need to grant access, but because + // it lets us declare a free operator like a member function. + friend std::ostream& operator<<(std::ostream& out, const center& ctr) + { + std::size_t padded = ctr.mLabel.length() + 2; + std::size_t left = (ctr.mWidth - padded) / 2; + std::size_t right = ctr.mWidth - left - padded; + return out << std::string(left, ctr.mFill) << ' ' << ctr.mLabel << ' ' + << std::string(right, ctr.mFill); + } + + std::string mLabel; + char mFill; + std::size_t mWidth; +}; + +/***************************************************************************** +* Four kinds of exceptions: derived from boost::exception, from +* std::exception, from both, from neither +*****************************************************************************/ +// Interestingly, we can't use this variant with BOOST_THROW_EXCEPTION() +// (which we want) -- we reach a failure topped by this comment: +// //All boost exceptions are required to derive from std::exception, +// //to ensure compatibility with BOOST_NO_EXCEPTIONS. +struct FromBoost: public boost::exception +{ + FromBoost(const std::string& what): mWhat(what) {} + ~FromBoost() throw() {} + std::string what() const { return mWhat; } + std::string mWhat; +}; + +struct FromStd: public std::runtime_error +{ + FromStd(const std::string& what): std::runtime_error(what) {} +}; + +struct FromBoth: public boost::exception, public std::runtime_error +{ + FromBoth(const std::string& what): std::runtime_error(what) {} +}; + +// Same deal with FromNeither: can't use with BOOST_THROW_EXCEPTION(). +struct FromNeither +{ + FromNeither(const std::string& what): mWhat(what) {} + std::string what() const { return mWhat; } + std::string mWhat; +}; + +/***************************************************************************** +* Two kinds of throws: plain throw and BOOST_THROW_EXCEPTION() +*****************************************************************************/ +template <typename EXC> +void plain_throw(const std::string& what) +{ + throw EXC(what); +} + +template <typename EXC> +void boost_throw(const std::string& what) +{ + BOOST_THROW_EXCEPTION(EXC(what)); +} + +// Okay, for completeness, functions that throw non-class values. We wouldn't +// even deign to consider these if we hadn't found examples in our own source +// code! (Note that Kakadu's internal exception support is still based on +// throwing ints.) +void throw_char_ptr(const std::string& what) +{ + throw what.c_str(); // umm... +} + +void throw_int(const std::string& what) +{ + throw int(what.length()); +} + +/***************************************************************************** +* Three sequences of catch clauses: +* boost::exception then ..., +* std::exception then ..., +* or just ... +*****************************************************************************/ +void catch_boost_dotdotdot(void (*thrower)(const std::string&), const std::string& what) +{ + try + { + thrower(what); + } + catch (const boost::exception& e) + { + std::cout << "catch (const boost::exception& e)" << std::endl; + std::cout << "e is " << typeid(e).name() << std::endl; + std::cout << "boost::diagnostic_information(e):\n'" + << boost::diagnostic_information(e) << "'" << std::endl; + // no way to report e.what() + } + catch (...) + { + std::cout << "catch (...)" << std::endl; + std::cout << "boost::current_exception_diagnostic_information():\n'" + << boost::current_exception_diagnostic_information() << "'" + << std::endl; + } +} + +void catch_std_dotdotdot(void (*thrower)(const std::string&), const std::string& what) +{ + try + { + thrower(what); + } + catch (const std::exception& e) + { + std::cout << "catch (const std::exception& e)" << std::endl; + std::cout << "e is " << typeid(e).name() << std::endl; + std::cout << "boost::diagnostic_information(e):\n'" + << boost::diagnostic_information(e) << "'" << std::endl; + std::cout << "e.what: '" + << e.what() << "'" << std::endl; + } + catch (...) + { + std::cout << "catch (...)" << std::endl; + std::cout << "boost::current_exception_diagnostic_information():\n'" + << boost::current_exception_diagnostic_information() << "'" + << std::endl; + } +} + +void catch_dotdotdot(void (*thrower)(const std::string&), const std::string& what) +{ + try + { + thrower(what); + } + catch (...) + { + std::cout << "catch (...)" << std::endl; + std::cout << "boost::current_exception_diagnostic_information():\n'" + << boost::current_exception_diagnostic_information() << "'" + << std::endl; + } +} + +/***************************************************************************** +* Try a particular kind of throw against each of three catch sequences +*****************************************************************************/ +void catch_several(void (*thrower)(const std::string&), const std::string& what) +{ + std::cout << std::string(20, '-') << "catch_boost_dotdotdot(" << what << ")" << std::endl; + catch_boost_dotdotdot(thrower, "catch_boost_dotdotdot(" + what + ")"); + + std::cout << std::string(20, '-') << "catch_std_dotdotdot(" << what << ")" << std::endl; + catch_std_dotdotdot(thrower, "catch_std_dotdotdot(" + what + ")"); + + std::cout << std::string(20, '-') << "catch_dotdotdot(" << what << ")" << std::endl; + catch_dotdotdot(thrower, "catch_dotdotdot(" + what + ")"); +} + +/***************************************************************************** +* For a particular kind of exception, try both kinds of throw against all +* three catch sequences +*****************************************************************************/ +template <typename EXC> +void catch_both_several(const std::string& what) +{ + std::cout << std::string(20, '*') << "plain_throw<" << what << ">" << std::endl; + catch_several(plain_throw<EXC>, "plain_throw<" + what + ">"); + + std::cout << std::string(20, '*') << "boost_throw<" << what << ">" << std::endl; + catch_several(boost_throw<EXC>, "boost_throw<" + what + ">"); +} + +/***************************************************************************** +* TUT +*****************************************************************************/ +namespace tut +{ + struct llexception_data + { + }; + typedef test_group<llexception_data> llexception_group; + typedef llexception_group::object object; + llexception_group llexceptiongrp("llexception"); + + template<> template<> + void object::test<1>() + { + set_test_name("throwing exceptions"); + + // For each kind of exception, try both kinds of throw against all + // three catch sequences + std::size_t margin = 72; + std::cout << center("FromStd", '=', margin) << std::endl; + catch_both_several<FromStd>("FromStd"); + + std::cout << center("FromBoth", '=', margin) << std::endl; + catch_both_several<FromBoth>("FromBoth"); + + std::cout << center("FromBoost", '=', margin) << std::endl; + // can't throw with BOOST_THROW_EXCEPTION(), just use catch_several() + catch_several(plain_throw<FromBoost>, "plain_throw<FromBoost>"); + + std::cout << center("FromNeither", '=', margin) << std::endl; + // can't throw this with BOOST_THROW_EXCEPTION() either + catch_several(plain_throw<FromNeither>, "plain_throw<FromNeither>"); + + std::cout << center("const char*", '=', margin) << std::endl; + // We don't expect BOOST_THROW_EXCEPTION() to throw anything so daft + // as a const char* or an int, so don't bother with + // catch_both_several() -- just catch_several(). + catch_several(throw_char_ptr, "throw_char_ptr"); + + std::cout << center("int", '=', margin) << std::endl; + catch_several(throw_int, "throw_int"); + } +} // namespace tut |