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Add some comments to __cxa_throw 

Maybe this will save the next person who has to look at this code some
time. Please don't blame me for the implementation, I'm just trying to
reconstruct what it does.
This commit is contained in:
Julian Brost 2020-10-20 14:02:42 +02:00
parent e60dd51284
commit 1ad233da86
1 changed files with 11 additions and 0 deletions
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11
lib/base/exception.cpp
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@ -101,6 +101,13 @@ void icinga::RethrowUncaughtException()
extern "C"
void __cxa_throw(void *obj, TYPEINFO_TYPE *pvtinfo, void (*dest)(void *))
{
/* This function overrides an internal function of libstdc++ that is called when a C++ exception is thrown in order
* to capture as much information as possible at that time and then call the original implementation. This
* information includes:
* - stack trace (for later use in DiagnosticInformation)
* - context trace (for later use in DiagnosticInformation)
*/
auto *tinfo = static_cast<std::type_info *>(pvtinfo);
typedef void (*cxa_throw_fn)(void *, std::type_info *, void (*)(void *)) __attribute__((noreturn));
@ -112,6 +119,7 @@ void __cxa_throw(void *obj, TYPEINFO_TYPE *pvtinfo, void (*dest)(void *))
l_LastExceptionDest.reset(new DestCallback(dest));
#endif /* !defined(__GLIBCXX__) && !defined(_WIN32) */
// resolve symbol to original implementation of __cxa_throw for the call at the end of this function
if (real_cxa_throw == nullptr)
real_cxa_throw = (cxa_throw_fn)dlsym(RTLD_NEXT, "__cxa_throw");
@ -121,10 +129,12 @@ void __cxa_throw(void *obj, TYPEINFO_TYPE *pvtinfo, void (*dest)(void *))
if (!uex) {
#endif /* NO_CAST_EXCEPTION */
// save the current stack trace in a thread-local variable
boost::stacktrace::stacktrace stack;
SetLastExceptionStack(stack);
#ifndef NO_CAST_EXCEPTION
// save the current stack trace in the boost exception error info if the exception is a boost::exception
if (ex && !boost::get_error_info<StackTraceErrorInfo>(*ex))
*ex << StackTraceErrorInfo(stack);
}
@ -134,6 +144,7 @@ void __cxa_throw(void *obj, TYPEINFO_TYPE *pvtinfo, void (*dest)(void *))
SetLastExceptionContext(context);
#ifndef NO_CAST_EXCEPTION
// save the current context trace in the boost exception error info if the exception is a boost::exception
if (ex && !boost::get_error_info<ContextTraceErrorInfo>(*ex))
*ex << ContextTraceErrorInfo(context);
#endif /* NO_CAST_EXCEPTION */