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Calling longjmp() prevents local class variables from being properly destroyed, as can be demonstrated by the following code:
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#include <csetjmp>
#include <iostream>
using namespace std;
static jmp_buf env;
class Counter {
public:
static int Instances;
Counter() {Instances++;}
~Counter() {Instances--;}
private:
Counter(const Counter& that);
Counter& operator=(const Counter& that);
};
int Counter::Instances = 0;
class Error {};
void func() {
Counter c;
cout << "func(): Instances: " << Counter::Instances << endl;
longjmp( env, 1);
}
int main() {
cout << "Before setjmp(): Instances: " << Counter::Instances << endl;
if (setjmp(env) == 0) {
func();
} else {
cout << "From longjmp(): Instances: " << Counter::Instances << endl;
}
cout << "After longjmp(): Instances: " << Counter::Instances << endl;
}
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Use exceptions instead of setjmp() and longjmp(), as throwing exceptions will still invoke destructors of local class variables.
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#include <iostream>
using namespace std;
class Counter {
public:
static int Instances;
Counter() {Instances++;}
~Counter() {Instances--;}
private:
Counter(const Counter& that);
Counter& operator=(const Counter& that);
};
int Counter::Instances = 0;
class Error {};
void func() {
Counter c;
cout << "func(): Instances: " << Counter::Instances << endl;
throw Error();
}
int main() {
cout << "Before try: Instances: " << Counter::Instances << endl;
try {
func();
} catch (...) {
cout << "In catch: Instances: " << Counter::Instances << endl;
}
cout << "After catch: Instances: " << Counter::Instances << endl;
}
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Before try: Instances: 0 func(): Instances: 1 In catch: Instances: 0 After catch: Instances: 0 |
Exceptions
ERR34-EX1: The longjmp() function may be safely invoked if you can guarantee that no nontrivial destructors are bypassed between the longjmp() call and the corresponding setjmp().
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