Allow strcasecmp on Windows, because sometimes only POSIX is provided…

… there.

configure.ac

@@ -83,6 +83,11 @@ AC_TYPE_UINT8_T
 # Checks for library functions.
 AC_CHECK_FUNCS([_NSGetExecutablePath])
 
+AX_STRING_STRCASECMP
+if test x"$ac_cv_string_strcasecmp" = "xno" ; then
+  AX_STRINGS_STRCASECMP
+fi
+
 AM_GNU_GETTEXT([external])
 AM_GNU_GETTEXT_VERSION([0.19])
 

include/posix_string_compat.h

@@ -23,13 +23,17 @@
 #ifndef _POSIX_STRING_COMPAT_H
 #define _POSIX_STRING_COMPAT_H
 
-#include <string.h>
-
-#ifndef USE_WINDOWS
-#include <strings.h>
-#define strcmpi(s1,s2) strcasecmp(s1,s2)
-#define strnicmp(s1,s2,len) strncasecmp(s1,s2,len)
+#ifdef HAVE_STRING_STRCASECMP
+  #include <string.h>
+  #define strcmpi(s1,s2) strcasecmp(s1,s2)
+  #define strnicmp(s1,s2,len) strncasecmp(s1,s2,len)
+#elif HAVE_STRINGS_STRCASECMP
+  #include <strings.h>
+  #define strcmpi(s1,s2) strcasecmp(s1,s2)
+  #define strnicmp(s1,s2,len) strncasecmp(s1,s2,len)
+#else
+  #include <string.h>
+  // platform provides strcmpi and strnicmp
 #endif
 
-
 #endif // _POSIX_STRING_COMPAT_H

m4/ax_string_strcasecmp.m4

@@ -0,0 +1,52 @@
+# ===========================================================================
+#   https://www.gnu.org/software/autoconf-archive/ax_string_strcasecmp.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_STRING_STRCASECMP
+#
+# DESCRIPTION
+#
+#   This macro tries to find strcasecmp() in string.h.
+#
+#   Use this macro in conjunction with AX_STRINGS_STRCASECMP in your
+#   configure.in like so:
+#
+#     AX_STRING_STRCASECMP
+#     if test x"$ac_cv_string_strcasecmp" = "xno" ; then
+#         AX_STRINGS_STRCASECMP
+#     fi
+#
+#   This will cause either HAVE_STRING_STRCASECMP or HAVE_STRINGS_STRCASECMP
+#   to be defined in config.h, which will tell your code what header to
+#   include to get strcasecmp()'s prototype.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Warren Young <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 9
+
+AU_ALIAS([ETR_STRING_STRCASECMP], [AX_STRING_STRCASECMP])
+AC_DEFUN([AX_STRING_STRCASECMP],
+[
+AC_CACHE_CHECK([for strcasecmp() in string.h], ac_cv_string_strcasecmp, [
+        AC_LINK_IFELSE([AC_LANG_PROGRAM(
+                [[#include <string.h>]],
+                [[strcasecmp("foo", "bar");]])],
+                [ac_cv_string_strcasecmp=yes],
+                [ac_cv_string_strcasecmp=no])
+])
+
+        if test x"$ac_cv_string_strcasecmp" = "xyes"
+        then
+                AC_DEFINE(HAVE_STRING_STRCASECMP, 1,
+                        [ Define if your system has strcasecmp() in string.h ])
+        fi
+]) dnl AX_STRING_STRCASECMP

m4/ax_strings_strcasecmp.m4

@@ -0,0 +1,41 @@
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_strings_strcasecmp.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_STRINGS_STRCASECMP
+#
+# DESCRIPTION
+#
+#   This macro tries to find strcasecmp() in strings.h. See the
+#   AX_STRING_STRCASECMP macro's commentary for usage details.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Warren Young <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 9
+
+AU_ALIAS([ETR_STRINGS_STRCASECMP], [AX_STRINGS_STRCASECMP])
+AC_DEFUN([AX_STRINGS_STRCASECMP],
+[ AC_CACHE_CHECK([for strcasecmp() in strings.h], ac_cv_strings_strcasecmp, [
+
+        AC_LINK_IFELSE(
+                [AC_LANG_PROGRAM([[#include <strings.h>]],
+                        [[strcasecmp("foo", "bar");]])],
+                [ac_cv_strings_strcasecmp=yes],
+                [ac_cv_strings_strcasecmp=no])
+])
+
+        if test x"$ac_cv_strings_strcasecmp" = "xyes"
+        then
+                AC_DEFINE(HAVE_STRINGS_STRCASECMP, 1,
+                        [ Define if your system has strcasecmp() in strings.h ])
+        fi
+]) dnl AX_STRINGS_STRCASECMP