session.begin();
            WtCursor cursor = session.openCursor(tableUri);
            cursor.setKey(1); // Seems to happen with any key type
            cursor.setValue(1);
            cursor.save(); // calls cursor->insert
            session.prepare(10); // calls prepare_transaction with a timestamp of 10
            session.rollback();

previously allocated by thread T0 here:
    #0 0x51baa2 in realloc /data/mci/bc90f05be614b5760ea98b96a5a10212/toolchain-builder/tmp/build-llvm.sh-2ni/llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:165:3
    #1 0x7faee7c0213f in __realloc_func /home/dgottlieb/xgen/wiredtiger/src/os_common/os_alloc.c:121
    #2 0x7faee7c02244 in __wt_realloc_noclear /home/dgottlieb/xgen/wiredtiger/src/os_common/os_alloc.c:158
    #3 0x7faee7c70715 in __wt_buf_grow_worker /home/dgottlieb/xgen/wiredtiger/src/support/scratch.c:47
    #4 0x7faee7b2fc02 in __wt_buf_grow /home/dgottlieb/xgen/wiredtiger/./src/include/buf.i:17
    #5 0x7faee7b2fc51 in __wt_buf_set /home/dgottlieb/xgen/wiredtiger/./src/include/buf.i:80
    #6 0x7faee7b30183 in __wt_txn_op_set_key /home/dgottlieb/xgen/wiredtiger/./src/include/txn.i:182
    #7 0x7faee7b33317 in __wt_row_modify /home/dgottlieb/xgen/wiredtiger/src/btree/row_modify.c:197
    #8 0x7faee7acbf86 in __cursor_row_modify /home/dgottlieb/xgen/wiredtiger/src/btree/bt_cursor.c:434
    #9 0x7faee7acd6cf in __wt_btcur_insert /home/dgottlieb/xgen/wiredtiger/src/btree/bt_cursor.c:865
    #10 0x7faee7b7c5f1 in __curfile_insert /home/dgottlieb/xgen/wiredtiger/src/cursor/cur_file.c:265
    #11 0x54ffc2 in WtCursor::save() /home/dgottlieb/xgen/scratch/./include/wt_raii.h:139:16
    #12 0x54e5b2 in main /home/dgottlieb/xgen/scratch/cursor_copy.cpp:29:20
    #13 0x7faee6b8282f in __libc_start_main /build/glibc-LK5gWL/glibc-2.23/csu/../csu/libc-start.c:291

freed by thread T0 here:
    #0 0x51b302 in free /data/mci/bc90f05be614b5760ea98b96a5a10212/toolchain-builder/tmp/build-llvm.sh-2ni/llvm/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:124:3
    #1 0x7faee7c0279d in __wt_free_int /home/dgottlieb/xgen/wiredtiger/src/os_common/os_alloc.c:301
    #2 0x7faee7c8b3f3 in __wt_buf_free /home/dgottlieb/xgen/wiredtiger/./src/include/buf.i:100
    #3 0x7faee7c8c9cb in __wt_txn_op_free /home/dgottlieb/xgen/wiredtiger/src/txn/txn_log.c:180
    #4 0x7faee7c81434 in __wt_txn_rollback /home/dgottlieb/xgen/wiredtiger/src/txn/txn.c:1371
    #5 0x7faee7c5d4a2 in __session_rollback_transaction /home/dgottlieb/xgen/wiredtiger/src/session/session_api.c:1740
    #6 0x550509 in WtSession::rollback() /home/dgottlieb/xgen/scratch/./include/wt_raii.h:315:16
    #7 0x54e5d9 in main /home/dgottlieb/xgen/scratch/cursor_copy.cpp:31:21
    #8 0x7faee6b8282f in __libc_start_main /build/glibc-LK5gWL/glibc-2.23/csu/../csu/libc-start.c:291

READ of size 1 at 0x602000005090 thread T0
    #0 0x48db23 in memcpy /data/mci/bc90f05be614b5760ea98b96a5a10212/toolchain-builder/tmp/build-llvm.sh-2ni/llvm/projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:792:5
    #1 0x7faee7c70774 in __wt_buf_grow_worker /home/dgottlieb/xgen/wiredtiger/src/support/scratch.c:55
    #2 0x7faee7ba20ab in __wt_buf_grow /home/dgottlieb/xgen/wiredtiger/./src/include/buf.i:17
    #3 0x7faee7ba218e in __wt_buf_set /home/dgottlieb/xgen/wiredtiger/./src/include/buf.i:80
    #4 0x7faee7ba5d06 in __wt_cursor_copy_release_item /home/dgottlieb/xgen/wiredtiger/src/cursor/cur_std.c:249
    #5 0x7faee7b78a60 in __cursor_copy_release /home/dgottlieb/xgen/wiredtiger/./src/include/cursor.i:28
    #6 0x7faee7b7f539 in __curfile_close /home/dgottlieb/xgen/wiredtiger/src/cursor/cur_file.c:485
    #7 0x7faee7c8147e in __wt_txn_rollback /home/dgottlieb/xgen/wiredtiger/src/txn/txn.c:1376
    #8 0x7faee7c5d4a2 in __session_rollback_transaction /home/dgottlieb/xgen/wiredtiger/src/session/session_api.c:1740
    #9 0x550509 in WtSession::rollback() /home/dgottlieb/xgen/scratch/./include/wt_raii.h:315:16
    #10 0x54e5d9 in main /home/dgottlieb/xgen/scratch/cursor_copy.cpp:31:21
    #11 0x7faee6b8282f in __libc_start_main /build/glibc-LK5gWL/glibc-2.23/csu/../csu/libc-start.c:291
    #12 0x473848 in _start (/home/dgottlieb/xgen/scratch/a.out+0x473848)