Created
November 22, 2017 07:53
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#ifndef TOKEN_PASTE | |
#define TOKEN_PASTE(x, y) x##y | |
#define TOKEN_PASTE2(x, y) TOKEN_PASTE(x, y) | |
#endif | |
template <typename L> | |
struct scope_guard | |
{ | |
L l_; | |
bool invoked_{false}; | |
scope_guard(L &&l) | |
: l_(std::move(l)) | |
{ | |
} | |
~scope_guard() | |
{ | |
invoke(); | |
} | |
void invoke() | |
{ | |
if (!invoked_) | |
{ | |
l_(); | |
invoked_ = false; | |
} | |
} | |
void cancel() | |
{ | |
invoked_ = true; | |
} | |
}; | |
template <typename T> | |
inline auto make_scope_guard(T &&l) | |
{ | |
return scope_guard<T>(std::forward<T>(l)); | |
} | |
#define DEFER(...) auto TOKEN_PASTE2(__deferred, __COUNTER__) = make_scope_guard([&] { __VA_ARGS__ }); | |
int main() | |
{ | |
int fd = open("/proc/self/pagemap", O_RDONLY|O_LARGEFILE); | |
// DEFER(close(fd);); | |
// or | |
// auto g = make_guard([fd]{ close(fd); }); | |
// | |
// potentially g.cancel() or g.invoke() if needed | |
return 0; | |
} |
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