https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=9ee8eacb8d60e4e8a55a3908a9b218fde752c258
commit 9ee8eacb8d60e4e8a55a3908a9b218fde752c258 Author: Thomas Wolff <[email protected]> AuthorDate: Mon Feb 2 00:00:00 2026 +0000 Commit: Corinna Vinschen <[email protected]> CommitDate: Mon Feb 2 18:31:12 2026 +0100 towupper/towlower: handle Turkic language special casing For case conversion, Unicode has a standard mapping and a separate list of mapping rules for special cases (file SpecialCasing.txt), some of which are also language-dependent (as configured via locale). However, most of these rules are context-dependent, e.g. Greek capital Sigma is lowered to two different small sigmas, depending on the position at the end of a word. The POSIX API function towupper and tolower cannot consider context as they work only on one character at a time. String casing functions are unfortunately not available. The only special case conversions that apply to a single character are i and I in Turkish and Azerbaijani, where i keeps the dot when capitalised (U+0130) and I keeps not having a dot when converted small (U+0131). The patch handles these special cases, based on locale consideration. (cherry picked from commit 4356ccd02c9c51a0b0f0babc483567c129ba5393) Diff: --- newlib/libc/ctype/towctrans.c | 2 +- newlib/libc/ctype/towctrans_l.c | 23 +++++++++++++++++++---- winsup/cygwin/release/3.6.7 | 3 +++ 3 files changed, 23 insertions(+), 5 deletions(-) diff --git a/newlib/libc/ctype/towctrans.c b/newlib/libc/ctype/towctrans.c index 176aa3d9dbdb..2cd34184e006 100644 --- a/newlib/libc/ctype/towctrans.c +++ b/newlib/libc/ctype/towctrans.c @@ -81,7 +81,7 @@ _towctrans_r (struct _reent *r, wctrans_t w) { if (w == WCT_TOLOWER || w == WCT_TOUPPER) - return towctrans_l (c, w, 0); + return towctrans_l (c, w, LC_GLOBAL_LOCALE); else { // skipping this because it was causing trouble (cygwin crash) diff --git a/newlib/libc/ctype/towctrans_l.c b/newlib/libc/ctype/towctrans_l.c index b829266a49cd..67aea920b423 100644 --- a/newlib/libc/ctype/towctrans_l.c +++ b/newlib/libc/ctype/towctrans_l.c @@ -69,9 +69,21 @@ bisearch (wint_t ucs, const struct caseconv_entry *table, int max) return 0; } +static int +isturk (struct __locale_t *locale) +{ + const char * loc = getlocalename_l (LC_CTYPE, locale); + if (!loc) + return 0; + return 0 == strncmp (loc, "tr", 2) || 0 == strncmp (loc, "az", 2); +} + static wint_t -toulower (wint_t c) +toulower (wint_t c, struct __locale_t *locale) { + if (c == 'I' && isturk (locale)) + return 0x131; // LATIN SMALL LETTER DOTLESS I + const struct caseconv_entry * cce = bisearch(c, caseconv_table, sizeof(caseconv_table) / sizeof(*caseconv_table) - 1); @@ -105,8 +117,11 @@ toulower (wint_t c) } static wint_t -touupper (wint_t c) +touupper (wint_t c, struct __locale_t *locale) { + if (c == 'i' && isturk (locale)) + return 0x130; // LATIN CAPITAL LETTER I WITH DOT ABOVE + const struct caseconv_entry * cce = bisearch(c, caseconv_table, sizeof(caseconv_table) / sizeof(*caseconv_table) - 1); @@ -145,9 +160,9 @@ towctrans_l (wint_t c, wctrans_t w, struct __locale_t *locale) wint_t u = _jp2uc_l (c, locale); wint_t res; if (w == WCT_TOLOWER) - res = toulower (u); + res = toulower (u, locale); else if (w == WCT_TOUPPER) - res = touupper (u); + res = touupper (u, locale); else { // skipping the errno setting that was previously involved diff --git a/winsup/cygwin/release/3.6.7 b/winsup/cygwin/release/3.6.7 index 050f6008084e..5285ba042a44 100644 --- a/winsup/cygwin/release/3.6.7 +++ b/winsup/cygwin/release/3.6.7 @@ -7,3 +7,6 @@ Fixes: - Allow changing primary group even when running with cygserver account caching. Addresses: https://cygwin.com/pipermail/cygwin/2026-January/259250.html + +- Correctly handle i->İ, I->ı conversion in turk lnd azerbaijani languages + (LC_CTYPE=tr_TR, tr_CY, az_AZ).
