On 06/23/2018 01:48 PM, George Hartzell wrote:
> 
> Hi All,
> 
> I'm ensuring that the Spack packager can build m4 on OS X High Sierra.
> 
> Here's my PR for them:
> 
>      https://github.com/spack/spack/pull/8559

Making someone chase a URL is not friendly for long-term archives. 
Here's a summary:

+With format string strictness, High Sierra also enforces that %n isn't used
+in dynamic format strings, but we should just disable its use on darwin in
+general.
+
+--- a/lib/vasnprintf.c.orig	2017-06-22 15:19:15.000000000 -0700
++++ b/lib/vasnprintf.c	2017-06-22 15:20:20.000000000 -0700
+@@ -4869,7 +4869,7 @@ VASNPRINTF (DCHAR_T *resultbuf, size_t *
+ #endif
+                   *fbp = dp->conversion;
+ #if USE_SNPRINTF
+-# if !(((__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3)) && 
!defined __UCLIBC__) || ((defined _WIN32 || defined __WIN32__) && ! 
defined __CYGWIN__))
++# if !defined(__APPLE__) && !(((__GLIBC__ > 2 || (__GLIBC__ == 2 && 
__GLIBC_MINOR__ >= 3)) && !defined __UCLIBC__) || ((defined _WIN32 || 
defined __WIN32__) && ! defined __CYGWIN__))
+                 fbp[1] = '%';
+                 fbp[2] = 'n';
+                 fbp[3] = '\0';

In other words, you are patching gnulib to work around MacOS's new 
strictness that prevents the POSIX-compliant use of %n within 
snprintf().  As similar patches have already been made in upstream 
gnulib, the next release of m4 should automatically work with newer 
MacOS by virtue of updating to a newer gnulib.