...
In this example, main() does several useful work but does not catch any exceptions. Consequently, any exceptions thrown will call std::terminate(), and might not destroy any objects owned by the program.
| Code Block | ||||
|---|---|---|---|---|
| ||||
int main(int argc, char** argv) {
Object object; // might not get destroyed if exception thrown
// do useful work
return 0;
}
|
...
In this code example, all exceptions are caught, allowing normal termination, even in the face of unexpected errors (albeit with an exit status indicating that an error occurred).
| Code Block | ||||
|---|---|---|---|---|
| ||||
int main(int argc, char** argv) {
Object object;
int exit_status = EXIT_SUCCESS;
try {
// do useful work
} catch (...) {
exit_status = EXIT_FAILURE;
}
return exit_status; // object gets destroyed here
}
|
...
An alternative is to wrap all of main()'s functionality inside a try-catch block and catch and handle exceptions by exiting with a status indicating an error to the invoking process.
| Code Block | ||||
|---|---|---|---|---|
| ||||
int main(int argc, char** argv) {
try {
Object object;
// do useful work
return 0; // object gets destroyed here
} catch (...) {
exit(EXIT_FAILURE);
}
}
|
...
In the following code example, the function f() claims to throw exception1 but actually throws exception2. Consequently control flow is diverted to std::unexpected, and the toplevel catch clause may not be invoked. (It is not invoked on Linux with G++ 4.3).
| Code Block | ||||
|---|---|---|---|---|
| ||||
using namespace std;
class exception1 : public exception {};
class exception2 : public exception {};
void f(void) throw( exception1) {
// ...
throw (exception2());
}
int main() {
try {
f();
return 0;
} catch (...) {
cerr << "F called" << endl;
}
return EXIT_FAILURE;
}
|
...
The following code example declares the same exception it actually throws
| Code Block | ||||
|---|---|---|---|---|
| ||||
using namespace std;
class exception1 : public exception {};
class exception2 : public exception {};
void f(void) throw( exception1) {
// ...
throw (exception1());
}
int main() {
try {
f();
return 0;
} catch (...) {
cerr << "F called" << endl;
}
return EXIT_FAILURE;
}
|
...