Ah, so UCRT does the right thing? I was not aware of this behavior for "POSIX" locale.
I still wonder whether MSVCRT's btowc succeeds when GetACP() != CP_UTF8. If it converts using code page retuned by GetACP(), this means that replacement has the same behavior. Otherwise, we might need to check return value of `___lc_codepage_func()`. However, should we return WEOF for bytes in range 128-255? I think it would be good to be consistent with MSVCRT's behavior, which seems to do so. - Kirill Makurin ________________________________ From: LIU Hao Sent: Tuesday, June 3, 2025 1:09 PM To: mingw-w64-public@lists.sourceforge.net; Kirill Makurin Subject: Re: [Mingw-w64-public] Inconsistent behavior of btowc with "C" locale 在 2025-6-1 17:23, Kirill Makurin 写道: > Hi, > > I have noticed that behavior of `btowc` function is inconsistent between > MSVCRT and UCRT when current locale is "C". > > UCRT's `btowc` converts bytes in range 128-255 as if source charset was > ISO-8859-1 (code page 28591). MSVCRT's (on Windows 11) fails and returns > `WEOF`. In the "C" and "POSIX" locale (they denote the same locale) this should be the standard behavior (https://pubs.opengroup.org/onlinepubs/9799919799/functions/btowc.html): [CX] In the POSIX locale, btowc() shall not return WEOF if c has a value in the range 0 to 255 inclusive. > I have attached a simple program which can be used to reproduce it. It takes > one argument which is locale string (you can use ".CodePage" for simplicity). > > I must mention that I have UTF-8 enabled globally, which means GetACP() == > CP_UTF8. If anyone can test on system where this is not the case, this would > be helpful. > > This made me wonder how mingw-w64 implements replacement for msvcr*.dll which > do not have it: It passes return value of ` > ___lc_codepage_func()` directly to `MultiByteToWideChar`. > Maybe it's necessary to check for "C" locale in there. -- Best regards, LIU Hao _______________________________________________ Mingw-w64-public mailing list Mingw-w64-public@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mingw-w64-public
