Re: A weird example of .toUTF16z concatination side-effects in wcsncat
On Thursday, 7 April 2022 at 12:51:26 UTC, Stanislav Blinov wrote:
On Thursday, 7 April 2022 at 10:50:35 UTC, BoQsc wrote:
wchar_t* clang_string = cast(wchar_t *)"AA";
You're witnessing undefined behavior. "AA" is a string
literal and is stored in the data segment. Mere cast to
wchar_t* does not make writing through that pointer legal.
Moreover, even if it was legal to write through it, that alone
wouldn't be sufficient. From documentation of `wcsncat`:
The behavior is undefined if the destination array is not
large enough for the contents of both str and dest and the
terminating null wide character.
`wcsncat` does not allocate memory, it expects you to provide a
sufficiently large mutable buffer. For example, like this:
```d
// ...
auto cls = new wchar_t[256];
cls[] = 0;
cls[0..10] = 'A';
wchar_t* clang_string = cls.ptr;
// ...
```
That is correct, the results are satisfying. I believe this
thread is resolved.
```
import std.stdio;
@system void main(){
import std.utf: toUTF16z, toUTF16;
import core.stdc.wchar_ : wcsncat, wcslen, wprintf;
import core.stdc.stdlib : wchar_t;
import core.sys.windows.winnt : LPCWSTR;
auto cls = new wchar_t[256];
cls[] = 0;
cls[0..10] = 'A';
wchar_t* clang_string = cls.ptr;
//wchar_t* clang_string = cast(wchar_t *)"AA";
wstring dlang_string = "BB"w; //< NEW,
same results
LPCWSTR winpointer_to_string = "CC";
wcsncat(clang_string, dlang_string.toUTF16z,
wcslen(dlang_string.toUTF16z));
// String output: AABB
wcsncat(clang_string, winpointer_to_string,
wcslen(winpointer_to_string));
// String output: AABBCC
// Expected string: AABBCC
wprintf(clang_string);
// String output: AABBCC
// Expected string: AABBCC
}
```
Re: A weird example of .toUTF16z concatination side-effects in wcsncat
On Thursday, 7 April 2022 at 10:50:35 UTC, BoQsc wrote: wchar_t* clang_string = cast(wchar_t *)"AA"; You're witnessing undefined behavior. "AA" is a string literal and is stored in the data segment. Mere cast to wchar_t* does not make writing through that pointer legal. Moreover, even if it was legal to write through it, that alone wouldn't be sufficient. From documentation of `wcsncat`: The behavior is undefined if the destination array is not large enough for the contents of both str and dest and the terminating null wide character. `wcsncat` does not allocate memory, it expects you to provide a sufficiently large mutable buffer. For example, like this: ```d // ... auto cls = new wchar_t[256]; cls[] = 0; cls[0..10] = 'A'; wchar_t* clang_string = cls.ptr; // ... ```
Re: A weird example of .toUTF16z concatination side-effects in wcsncat
On Thursday, 7 April 2022 at 11:03:39 UTC, Tejas wrote:
On Thursday, 7 April 2022 at 10:50:35 UTC, BoQsc wrote:
Here I try to concatenate three character strings using
`wcsncat()`.
[...]
Maybe try using `wstring` instead of string? Also use the `w`
postfix
```d
wstring dlang_string = "BBB"w;
I can't test because I'm not on my PC and I don't use Windows
Exactly same results. `AA`
```
import std.stdio;
@system void main(){
import std.utf: toUTF16z, toUTF16;
import core.stdc.wchar_ : wcsncat, wcslen, wprintf;
import core.stdc.stdlib : wchar_t;
import core.sys.windows.winnt : LPCWSTR;
wchar_t* clang_string = cast(wchar_t *)"AA";
wstring dlang_string = "BBB"w; //< NEW,
same results
LPCWSTR winpointer_to_string = "CC";
wcsncat(clang_string, dlang_string.toUTF16z,
wcslen(dlang_string.toUTF16z));
// String output: AABBB
wcsncat(clang_string, winpointer_to_string,
wcslen(winpointer_to_string));
// String output: AA
// Expected string: AABBBCC
wprintf(clang_string);
// String output: AA
// Expected string: AABBBCC
}
```
Re: A weird example of .toUTF16z concatination side-effects in wcsncat
On Thursday, 7 April 2022 at 10:50:35 UTC, BoQsc wrote: Here I try to concatenate three character strings using `wcsncat()`. [...] Maybe try using `wstring` instead of string? Also use the `w` postfix ```d wstring dlang_string = "BBB"w; I can't test because I'm not on my PC and I don't use Windows
A weird example of .toUTF16z concatination side-effects in wcsncat
Here I try to concatenate three character strings using
`wcsncat()`.
`clang_string` AA
`dlang_string` BBB
`winpointer_to_string` CC
```
import std.stdio;
@system void main(){
import std.utf: toUTF16z, toUTF16;
import core.stdc.wchar_ : wcsncat, wcslen, wprintf;
import core.stdc.stdlib : wchar_t;
import core.sys.windows.winnt : LPCWSTR;
wchar_t* clang_string = cast(wchar_t *)"AA";
string dlang_string = "BBB";
LPCWSTR winpointer_to_string = "CC";
wcsncat(clang_string, dlang_string.toUTF16z,
wcslen(dlang_string.toUTF16z));
// String output: AABBB
wcsncat(clang_string, winpointer_to_string,
wcslen(winpointer_to_string));
// String output: AA
// Expected string: AABBBCC
wprintf(clang_string);
// String output: AA
// Expected string: AABBBCC
}
```
**Problem:**
Any *following concatenated string* after "`wcsncat()`
concatenation of `dlang_string.toUTF16z` string", happen to not
be printed and gets overwritten.
**The Expected output:**
I was expecting the `wprintf()` **result** to be
`AABBBCC`
The `wprintf() ` **result** I've received is this:
`AA`
