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#include <csetjmp>
#include <iostream>
static jmp_buf env;
struct Counter {
static int Instancesinstances;
Counter() { ++Instancesinstances; }
~Counter() { --Instancesinstances; }
};
int Counter::Instancesinstances = 0;
void f() {
Counter c;
std::cout << "f(): Instances: " << Counter::Instancesinstances << std::endl;
std::longjmp(env, 1);
}
int main() {
std::cout << "Before setjmp(): Instances: " << Counter::Instancesinstances << std::endl;
if (setjmp(env) == 0) {
f();
} else {
std::cout << "From longjmp(): Instances: " << Counter::Instancesinstances << std::endl;
}
std::cout << "After longjmp(): Instances: " << Counter::Instancesinstances << std::endl;
}
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Implementation Details
The above code produces the following results when compiled with Clang 3.5 8 for Linux, demonstrating that the undefined behavior in this instance is to fail to destroy the local Counter instance when the execution of f() is terminated:
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#include <iostream>
struct Counter {
static int Instancesinstances;
Counter() { ++Instancesinstances; }
~Counter() { --Instancesinstances; }
};
int Counter::Instancesinstances = 0;
void f() {
Counter c;
std::cout << "f(): Instances: " << Counter::Instancesinstances << std::endl;
throw "Exception";
}
int main() {
std::cout << "Before throw: Instances: " << Counter::Instancesinstances << std::endl;
try {
f();
} catch (const char *E) {
std::cout << "From catch: Instances: " << Counter::Instancesinstances << std::endl;
}
std::cout << "After catch: Instances: " << Counter::Instancesinstances << std::endl;
}
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which produces the following output:
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