idn: clarify null-termination on Windows#19980
Closed
vszakats wants to merge 2 commits into
Closed
Conversation
https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-multibytetowidechar https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-widechartomultibyte https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntoascii https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntounicode WINE source code: https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/kernelbase/locale.c https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale.c https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale_private.h Ref: curl#19976 (comment) Follow-up to 6694a42 curl#19798
bagder
approved these changes
Dec 15, 2025
There was a problem hiding this comment.
Pull request overview
Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
vszakats
changed the title
jay
approved these changes
Dec 16, 2025
Member
Author
|
Thanks for reviewing! |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Add comments to clarify that a terminating null is always present in
the buffers returned to the caller.
The curl APIs
win32_idn_to_ascii()orwin32_ascii_to_idn()receivea null-terminated UTF-8 string as input. They first convert it to wide
chars by first asking
MultiByteToWideChar()to calculate the length,by passing -1. This API returns the length with the null char included
(=
strlen() + 1), does the conversion, with the output alsonull-terminated.
IdnTo*()preserve this null character as documented.Then we pass this null-terminated, fixed-length buffer ito
WideCharToMultiByte(), which keeps preserving the null, ending up inthe buffer returned to the caller.
Refs:
https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-multibytetowidechar
https://learn.microsoft.com/windows/win32/api/stringapiset/nf-stringapiset-widechartomultibyte
https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntoascii
https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-idntounicode
WINE source code:
https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/kernelbase/locale.c
https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale.c
https://gitlab.winehq.org/wine/wine/-/blob/wine-10.20/dlls/ntdll/locale_private.h
Ref: #19976 (comment)
Follow-up to 6694a42 #19798