small_vector<T,n>::swap( ) appears to be broken

[benjamin.redelings@…]

The small_vector class seems like it could be really useful! However, it seems to have a broken implementation of the swap( ) member function.

The first test case creates a small_vector<int,10> of size 2. Swapping fails to clear the vector that is swapped from.

bredelings@transposon:~/Devel/bali-phy/master$ g++ test.C -I boost/include/ -std=c++14 bredelings@transposon:~/Devel/bali-phy/master$ ./a.out v.size() = 2 w.size() = 0

swapping v and w ...

v.size() = 2 w.size() = 2

The second test case creates a small_vector<int,10> of size 11. Swapping seems to work, but apparently corrupts the heap:

bredelings@transposon:~/Devel/bali-phy/master$ g++ test2.C -I boost/include/ -std=c++14 bredelings@transposon:~/Devel/bali-phy/master$ ./a.out v.size() = 11 w.size() = 0

swapping v and w ...

v.size() = 0 w.size() = 11 * Error in `./a.out': munmap_chunk(): invalid pointer: 0x00007ffd88feb978 * Aborted

[benjamin.redelings@…]

second test case

[benjamin.redelings@…]

It seems that when executing test2.C, the small_vector w is correctly destroyed, but v is incorrectly destroyed.

[Ion Gaztañaga]

Thanks for the report. The swap code handling the non-usual pointer swap idiom was not deleting the final elements. Also, an argument passed to test is the storage is propagable had a copy-paste error.

Fixed in:

​https://github.com/boostorg/container/commit/f1f97518d338c7f7351308aa1785ebae5f2ddde7