1 files changed, 40 insertions, 0 deletions

diff --git a/gl/m4/iswblank.m4 b/gl/m4/iswblank.m4
new file mode 100644
index 00000000..2c301a97
--- /dev/null
+++ b/gl/m4/iswblank.m4
@@ -0,0 +1,40 @@
+# iswblank.m4
+# serial 7
+dnl Copyright (C) 2011-2026 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+dnl This file is offered as-is, without any warranty.
+
+AC_DEFUN([gl_FUNC_ISWBLANK],
+[
+  AC_REQUIRE([gl_WCTYPE_H_DEFAULTS])
+  AC_REQUIRE([gl_WCTYPE_H])
+  dnl Persuade glibc <wctype.h> to declare iswblank().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  gl_CHECK_FUNCS_ANDROID([iswblank], [[#include <wctype.h>]])
+  AC_CHECK_DECLS([iswblank], , , [[
+    #include <wchar.h>
+    #include <wctype.h>
+  ]])
+  if test $ac_cv_func_iswblank = no; then
+    HAVE_ISWBLANK=0
+    if test $ac_cv_have_decl_iswblank = yes \
+       || case "$gl_cv_onwards_func_iswblank" in \
+            future*) true ;; \
+            *) false ;; \
+          esac; then
+      REPLACE_ISWBLANK=1
+    fi
+  fi
+  if test $HAVE_ISWCNTRL = 0 || test $REPLACE_ISWCNTRL = 1; then
+    dnl Redefine all of iswcntrl, ..., towupper in <wctype.h>.
+    :
+  else
+    if test $HAVE_ISWBLANK = 0 || test $REPLACE_ISWBLANK = 1; then
+      dnl Redefine only iswblank.
+      :
+    fi
+  fi
+
+])