Created attachment 8866 [details]
hostcc files patch for the reported issue

These seemed hidden/resolved in 1.26.1 to now, and some from back then (lxdialog's checklist menubox and util) remain resolved, but with 1.32+ these warnings are back on a Cygwin host compile:

  HOSTCC  scripts/basic/fixdep
In file included from scripts/basic/fixdep.c:114:
scripts/basic/fixdep.c: In function ‘parse_config_file’:
scripts/basic/fixdep.c:237:17: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  if (!(isalnum(*p) || *p == '_'))
                ^~
scripts/basic/fixdep.c:254:33: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  while (p <= end_3 && (isalnum(*p) || *p == '_'))
                                ^~
scripts/basic/fixdep.c:262:18: warning: array subscript has type ‘char’ [-Wchar-subscripts]
   if (!(isalnum(*q) || *q == '_'))
                 ^~
scripts/basic/fixdep.c: In function ‘parse_dep_file’:
scripts/basic/fixdep.c:338:28: warning: array subscript has type ‘char’ [-Wchar-subscripts]
   do p--; while (!isalnum(*p));
                           ^~
  HOSTCC  scripts/basic/split-include
In file included from scripts/basic/split-include.c:25:
scripts/basic/split-include.c: In function ‘main’:
scripts/basic/split-include.c:119:39: warning: array subscript has type ‘char’ [-Wchar-subscripts]
 for (itarget = 0; !isspace(str_config[itarget]); itarget++)
                            ~~~~~~~~~~^~~~~~~~~
  HOSTCC  scripts/basic/docproc
In file included from scripts/basic/docproc.c:37:
scripts/basic/docproc.c: In function ‘find_export_symbols’:
scripts/basic/docproc.c:190:20: warning: array subscript has type ‘char’ [-Wchar-subscripts]
    while (isalnum(*p) || *p == '_')
                   ^~
scripts/basic/docproc.c:193:20: warning: array subscript has type ‘char’ [-Wchar-subscripts]
    while (isspace(*p))
                   ^~
scripts/basic/docproc.c:199:20: warning: array subscript has type ‘char’ [-Wchar-subscripts]
    while (isspace(*p))
                   ^~
scripts/basic/docproc.c:202:20: warning: array subscript has type ‘char’ [-Wchar-subscripts]
    while (isalnum(*e) || *e == '_')
                   ^~
scripts/basic/docproc.c: In function ‘singfunc’:
scripts/basic/docproc.c:269:19: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  if (isspace(line[i])) {
              ~~~~^~~
scripts/basic/docproc.c: In function ‘parse_file’:
scripts/basic/docproc.c:302:28: warning: array subscript has type ‘char’ [-Wchar-subscripts]
     while (*s && !isspace(*s)) s++;
                           ^~
scripts/basic/docproc.c:307:28: warning: array subscript has type ‘char’ [-Wchar-subscripts]
     while (*s && !isspace(*s)) s++;
                           ^~
scripts/basic/docproc.c:312:28: warning: array subscript has type ‘char’ [-Wchar-subscripts]
     while (*s && !isspace(*s)) s++;
                           ^~
scripts/basic/docproc.c:318:28: warning: array subscript has type ‘char’ [-Wchar-subscripts]
     while (*s && !isspace(*s)) s++;
                           ^~
scripts/basic/docproc.c:321:21: warning: array subscript has type ‘char’ [-Wchar-subscripts]
     while (isspace(*s))
                    ^~
  HOSTCC  scripts/kconfig/conf.o
In file included from scripts/kconfig/conf.c:8:
scripts/kconfig/conf.c: In function ‘strip’:
scripts/kconfig/conf.c:47:18: warning: array subscript has type ‘char’ [-Wchar-subscripts]
 while ((isspace(*p)))
                 ^~
scripts/kconfig/conf.c:55:18: warning: array subscript has type ‘char’ [-Wchar-subscripts]
 while ((isspace(*p)))
                 ^~
scripts/kconfig/conf.c: In function ‘conf_choice’:
scripts/kconfig/conf.c:404:25: warning: array subscript has type ‘char’ [-Wchar-subscripts]
   else if (isdigit(line[0]))
                    ~~~~^~~
  HOSTCC  scripts/kconfig/mconf.o
In file included from scripts/kconfig/mconf.c:17:
scripts/kconfig/mconf.c: In function ‘conf’:
scripts/kconfig/mconf.c:774:49: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  for (i = 0; input_buf[i] && !isspace(input_buf[i]); i++)
                                       ~~~~~~~~~^~~
  HOSTCC  scripts/kconfig/zconf.tab.o
In file included from scripts/kconfig/zconf.tab.c:142:
scripts/kconfig/confdata.c: In function ‘conf_expand_value’:
scripts/kconfig/confdata.c:57:18: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  while (isalnum(*src) || *src == '_')
                 ^~~~
  HOSTCC  applets/applet_tables
In file included from applets/applet_tables.c:18:
applets/applet_tables.c: In function ‘str_isalnum_’:
applets/applet_tables.c:55:16: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  if (!isalnum(*s) && *s != '_')
               ^~

I found an old thread where Denys supplied a potential fix for fixdep and I applied similar to docproc and the others, so here's an updated version of that patch covering all of the above.