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52 lines
1.3 KiB
52 lines
1.3 KiB
4 years ago
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Optional Empty Access warnings are reported when we try to retrieve the value of a [`folly::Optional`](https://github.com/facebook/folly/blob/master/folly/Optional.h) when it is empty (i.e. `folly::none`).
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In the following example we get a warning as `int_opt` might be `folly::none` and its value is being accessed:
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```cpp
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bool somef(int v);
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folly::Optional<int> mightReturnNone(int v) {
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if (somef(v)) {
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return folly::Optional(v);
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}
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return folly::none;
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}
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int value_no_check() {
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folly::Optional<int> int_opt = mightReturnNone (4);
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return int_opt.value(); // Optional Empty Access warning
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}
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```
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We do not get the warning anymore if we add a check whether `int_opt` is not empty:
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```cpp
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int value_check() {
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folly::Optional<int> int_opt = mightReturnNone (4);
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if (int_opt.has_value()) {
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return int_opt.value(); // OK
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}
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return -1;
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}
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```
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In some cases we know that we have a non-empty value and there is no need to have a check. Consider the following example where Infer does not warn:
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```cpp
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bool somef(int v) {return v > 3;};
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folly::Optional<int> mightReturnNone(int v) {
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if (somef(v)) {
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return folly::Optional(v);
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}
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return folly::none;
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}
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int value_no_check() {
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folly::Optional<int> int_opt = mightReturnNone (4); // cannot be folly::none
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return int_opt.value(); // OK
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}
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```
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