build: use the system printf routines in most cases

glibc <= 2.5 would crash when passed invalid long double values,
therefore internal gnulib routines were used, essentially only by od,
to output such invalid values.  Later glibc versions don't crash,
as per https://sourceware.org/bugzilla/show_bug.cgi?id=4586
and subsequently od was adjusted to use the system printf routines
through the use of the ftoastr module with commit v8.7-22-ga71c22f.
Consequently our testing of this feature was moot, and use of
the gnulib printf replacement for printf(1), od(1) and error(3) etc.
was redundant.

* configure.ac (gl_printf_safe): Unset so that we don't check that
"nan" is output for these long double values.
* tests/misc/od-float.sh: Adjust all existing checks to fail if od
exits with failure status (like crashing for example).  Add a new case
for one of the problematic invalid long double values for x86_64.
We only check that od exits successfully at present, which may change
if https://sourceware.org/bugzilla/show_bug.cgi?id=17661 is resolved.

configure.ac

@@ -67,6 +67,12 @@ cu_have_perl=yes
 case $PERL in *"/missing "*) cu_have_perl=no;; esac
 AM_CONDITIONAL([HAVE_PERL], [test $cu_have_perl = yes])
 
+# Disable the checks for handling certain invalid long double values
+# since this results in always replacing the printf() implementation
+# (see https://sourceware.org/bugzilla/show_bug.cgi?id=17661) and
+# od (ftoastr) doesn't use the replacement anyway.
+m4_divert_text([INIT_PREPARE], [gl_printf_safe=''])
+
 # gl_GCC_VERSION_IFELSE([major], [minor], [run-if-found], [run-if-not-found])
 # ------------------------------------------------
 # If $CPP is gcc-MAJOR.MINOR or newer, then run RUN-IF-FOUND.

tests/misc/od-float.sh

@@ -29,7 +29,7 @@ export LC_ALL=C
 # on x86: sometimes there was no space between the columns.
 
 set x $(echo aaaabaaa | tr ab '\376\377' | od -t fF) ||
-  framework_failure_
+  fail=1
 case "$*" in
 *0-*) fail=1;;
 esac
@@ -38,7 +38,7 @@ case $3,$4 in
 esac
 
 set x $(echo aaaaaaaabaaaaaaa | tr ab '\376\377' | od -t fD) ||
-  framework_failure_
+  fail=1
 case "$*" in
 *0-*) fail=1;;
 esac
@@ -47,7 +47,7 @@ case $3,$4 in
 esac
 
 set x $(echo aaaaaaaaaaaaaaaabaaaaaaaaaaaaaaa | tr ab '\376\377' | od -t fL) ||
-  framework_failure_
+  fail=1
 case "$*" in
 *0-*) fail=1;;
 esac
@@ -55,4 +55,18 @@ case $3,$4 in
 -1.023442870282055988e+4855,-1.023442870282055988e+4855) fail=1;;
 esac
 
+# Ensure od doesn't crash as it did on glibc <= 2.5:
+# https://sourceware.org/bugzilla/show_bug.cgi?id=4586
+set x $(printf 00000000ff000000 | tr 0f '\000\377' | od -t fL) || fail=1
+# With coreutils <= 8.7 we used to print "nan" for the above invalid value.
+# However since v8.7-22-ga71c22f we deferred to the system printf routines
+# through the use of the ftoastr module.  So the following check would only
+# be valid on x86_64 if we again handle the conversion internally or
+# if this glibc bug is resolved:
+# https://sourceware.org/bugzilla/show_bug.cgi?id=17661
+#case "$*" in
+#*nan*) ;;
+#*) fail=1;;
+#esac
+
 Exit $fail