libcxx: fix a subtle string bug caused by not doing small string optimization #296
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…mization the implementation of to_string() passes the address of the first element of a default-initialized string to snprintf. Normally, this is always a valid address because of the sso, but in Cheerp we don't do it so the size is 0 and the address is invalid. As a fix we initialize the string with an initial size > 0.
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Pull Request Overview
This PR addresses a bug in the implementation of to_string() caused by relying on small string optimization, which is not available in Cheerp.
- Replace default-initialized string construction with a fixed-size initialization to ensure a valid internal buffer.
- Adjust the string size to match its capacity after initialization.
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| template <> | ||
| struct initial_string<string> { | ||
| string operator()() const { |
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[nitpick] Consider adding a comment explaining the choice of the fixed size '20' to clarify its sufficiency for preventing the invalid address issue in Cheerp.
Suggested change
| string operator()() const { | |
| string operator()() const { | |
| // The fixed size '20' is chosen as an initial buffer size to ensure | |
| // sufficient space for typical use cases and to prevent invalid address | |
| // issues in Cheerp. The size can dynamically grow if needed. |
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the implementation of to_string() passes the address of the first element of a default-initialized string to snprintf. Normally, this is always a valid address because of the sso, but in Cheerp we don't do it so the size is 0 and the address is invalid. As a fix we initialize the string with an initial size > 0.