A question about postblit constructor

[Mike Parker]

On Tuesday, 5 November 2019 at 10:32:03 UTC, Ferhat Kurtulmuş 
wrote:
> On Tuesday, 5 November 2019 at 10:31:05 UTC, Ferhat Kurtulmuş 
> wrote:
>> On Tuesday, 5 November 2019 at 10:13:59 UTC, Mike Parker wrote:
>>> [...]
>>
>> Yep, it is obvious that my code is wrong. s1 and s2 point to 
>> the same memory address. I could obtain my desired behavior 
>> with copy constructor. The documentation also say "WARNING: 
>> The postblit is considered legacy and is not recommended for 
>> new code. Code should use copy constructors defined in the 
>> previous section".
>>

I meant the example as an answer to your statement, "I wonder how 
new memory is allocated without an explicit malloc here". The 
postblit was intended as a chance to "fixup" everything when you 
needed a deep copy. The new struct is initialized as a shallow 
copy, so when you enter into the postblit, the pointer is already 
pointing at the original location. Without assigning it a new 
malloc'ed address, your memcpy was essentially overwriting the 
original location with its own data.