*printf: Avoid "expanded before it was required" warning

[Bruno Haible]

In GNU libtextstyle I'm seeing this warning:

configure.ac:71: warning: AC_REQUIRE: `gl_SNPRINTF_TRUNCATION_C99' was expanded 
before it was required
configure.ac:71: 
http://www.gnu.org/software/autoconf/manual/autoconf.html#Expanded-Before-Required
gnulib-m4/vasnprintf.m4:15: gl_REPLACE_VASNPRINTF is expanded from...
gnulib-m4/snprintf-posix.m4:7: gl_FUNC_SNPRINTF_POSIX is expanded from...
gnulib-m4/gnulib-comp.m4:222: lts_INIT is expanded from...
configure.ac:71: the top level

This patch fixes it.


2020-10-11  Bruno Haible  <bruno@clisp.org>

        *printf: Avoid "expanded before it was required" warning.
        * m4/printf.m4 (gl_SNPRINTF_TRUNCATION_C99): Define through
        AC_DEFUN_ONCE.

diff --git a/m4/printf.m4 b/m4/printf.m4
index c6a7ef6..eeb792b 100644
--- a/m4/printf.m4
+++ b/m4/printf.m4
@@ -1,4 +1,4 @@
-# printf.m4 serial 69
+# printf.m4 serial 70
 dnl Copyright (C) 2003, 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -1198,7 +1198,7 @@ dnl Test whether the string produced by the snprintf 
function is always NUL
 dnl terminated. (ISO C99, POSIX:2001)
 dnl Result is gl_cv_func_snprintf_truncation_c99.
 
-AC_DEFUN([gl_SNPRINTF_TRUNCATION_C99],
+AC_DEFUN_ONCE([gl_SNPRINTF_TRUNCATION_C99],
 [
   AC_REQUIRE([AC_PROG_CC])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles