[5.8] [stdlib] Fix String.reserveCapacity underallocation #65988
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When called on a string that is not uniquely referenced, `String.reserveCapacity(_:)` ignores the current capacity, using the passed-in capacity for the size of its new storage. This can result in an underallocation and write past the end of the new buffer. This fix changes the new size calculation to use the current UTF-8 count as the minimum. Non-native or non-unique strings now allocate the requested capacity (or space enough for the current contents, if that's larger than what's requested). rdar://109275875 Fixes apple#53483
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@swift-ci Please test |
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cc @apple/swift5-branch-managers |
watchOS devices can have different allocation characteristics from other devices. This modifies the string capacity growth tests to be more flexible about measuring the growth in capacity, specifically when more is allocated than requested.
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@swift-ci Please test |
stephentyrone
approved these changes
Jul 25, 2023
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This is a cherry pick of #65902 for the 5.8 branch.
When called on a string that is not uniquely referenced,
String.reserveCapacity(_:)ignores the current capacity, using the passed-in capacity for the size of its new storage. This can result in an underallocation and write past the end of the new buffer.This fix changes the new size calculation to use the current UTF-8 count as the minimum. Non-native or non-unique strings now allocate the requested capacity (or space enough for the current contents, if that's larger than what's requested).
rdar://109275875
Fixes #53483