Close #13415: Test in configure if unsetenv() has a return value or not.
Patch written by Charles-François Natali.
diff --git a/configure b/configure
index 596336e..112c20a 100755
--- a/configure
+++ b/configure
@@ -9812,6 +9812,34 @@
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for broken unsetenv" >&5
+$as_echo_n "checking for broken unsetenv... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+#include <stdlib.h>
+
+int
+main ()
+{
+int res = unsetenv("DUMMY")
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+else
+
+$as_echo "#define HAVE_BROKEN_UNSETENV 1" >>confdefs.h
+
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
for ac_prog in true
do
# Extract the first word of "$ac_prog", so it can be a program name with args.