Is std::uncaught_exceptions useful for avoiding all exceptions? [duplicate] - c++

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How to catch segmentation fault in Linux?
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I need to catch segmentation fault and other unknown exceptions in my application. But I do not know how I can do that!
Can I use std::uncaught_exceptions for this aim?

Answer 1

Can I use std::uncaught_exceptions for this aim?
Consider this code:
int main(int argc, char* argv[])
{
int *val = NULL;
*val = 1;
std::cout << "uncaught: " << std::uncaught_exceptions() << std::endl;
return 0;
}
This will likely cause a segmentation fault and nothing will be output.
I need to catch segmentation fault and other unknown exceptions in my application. But I do not know how I can do that!
Exception handling in C++ can be done through the try-catch block, and you could use the std::signal function to catch certain errors like SIGSEGV, SIGFPE, or SIGILL, example:
#include <iostream>
#include <exception>
#include <csignal>
#include <cstdio>
extern "C" {
void sig_fn(int sig)
{
printf("signal: %d\n", sig);
std::exit(-1);
}
}
int main(int argc, char* argv[])
{
int *val = NULL;
std::signal(SIGSEGV, sig_fn);
try {
*val = 1;
} catch (...) {
std::cout << "..." << std::endl;
}
if (std::uncaught_exception()) {
std::cout << "uncaught" << std::endl;
}
std::cout << "return" << std::endl;
return 0;
}
But you should note that this type of exception handling is really meant to do clean-up and shutdown, not necessarily catch and release; take this code for example:
#include <iostream>
#include <exception>
#include <csignal>
#include <cstdio>
extern "C" {
void sig_fn(int sig)
{
printf("signal: %d\n", sig);
}
}
int main(int argc, char* argv[])
{
int *val = NULL;
std::signal(SIGSEGV, sig_fn);
while (true) {
try {
*val = 1;
} catch (...) {
std::cout << "..." << std::endl;
}
}
if (std::uncaught_exception()) {
std::cout << "uncaught" << std::endl;
}
std::cout << "return" << std::endl;
return 0;
}
This code will cause and catch the segmentation fault forever!
If you are trying to catch a segmentation fault, you need to investigate why the segmentation fault (or any error for that matter) happened in the first place and correct that issue; using the above code as an example:
int *val = NULL;
if (val == NULL) {
std::cout << "Handle the null!" << std::endl;
} else {
*val = 1;
}
For further reading: here is a SO Q&A on what a segfault is, as well, here is the Wiki on it, and MIT has some tips on handling and debugging segfaults too.
Hope that can help.