On 3/27/2019 at 8:06 PM, jt.tarigan said:
It always returns an error (L'Buffer is too small). I don't get it since the destination length and source is the same, and dst is actually larger than src. But when I changed the code to this
If there are 442 characters in a string (the length of actual characters, not including the null terminator), then the destination buffer needs to have enough space to store 443 characters so that it can write a null terminator at the end of the string. Some string handling functions would simply truncatthe string in this situation (drop the last character and replace it with the null terminator), while others would simple not write the null terminator at all and leave you in a very dangerous situation, but strncpy_s is specified to do nothing and return an error when the destination buffer is too small. The docs are here: https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/strncpy-s-strncpy-s-l-wcsncpy-s-wcsncpy-s-l-mbsncpy-s-mbsncpy-s-l?view=vs-2017
When doing manual C-style string manipulation, it's important to know which of these functions deals with length in characters including the terminator, which ones work with length in characters without the terminator, and which ones deal with length in bytes of a memory allocation. Always check the documentation.
1 hour ago, jt.tarigan said:
I decided to keep using this one:
strncpy_s(dst, 1024,src, 442);
I've read somewhere that this is probably the best solution
To be frank, that's voodoo coding / cargo cult coding, and doing random things with raw byte array management that seems to work without deep understanding of why, is not a recipe for stable software. Memory corruption lies that way...
If dst is actually a static size of 1kb though, then yeah, this is correct -- "copy a C string of length 442 (not counting the terminator) into this 1kb allocation".
If dst is a fixed size array, like "char dst[1024]", then you can avoid human error by calling "strncpy_s(dst, src, length)" and the destination size of 1025 will be inferred automatically.
18 hours ago, alvaro said:
Why are you manipulating zero-terminated char buffers, instead of using std::string?
I couldn't care less about the reputation system on these forums, but it would be better if the people who are downvoting my question could explain what they think is wrong with it. That way we can have a conversation.
Sorry, I downvoted this because it's a straightforward question of 'how does this account function work', and that function has many uses in places where std::string is a shitty solution.
But, I didn't notice the OP has tagged this as a C++ question and is going to just arbitrarily tweak numbers to make it work, so, yeah, using std::string is entirely appropriate here ?
