Define "random_device" effective target

Currently only matches targets where _GLIBCXX_USE_RANDOM_TR1 is defined,
which means /dev/random and /dev/urandom are usable.

	* testsuite/25_algorithms/make_heap/complexity.cc: Require effective
	target for std::random_device.
	* testsuite/26_numerics/random/random_device/cons/default.cc:
	Likewise.
	* testsuite/experimental/algorithm/sample-2.cc: Likewise.
	* testsuite/experimental/algorithm/shuffle.cc: Likewise.
	* testsuite/experimental/random/randint.cc: Likewise.
	* testsuite/lib/libstdc++.exp
	(check_effective_target_random_device): New proc.

From-SVN: r262415

libstdc++-v3/ChangeLog

@@ -1,3 +1,15 @@
+2018-07-04  Jonathan Wakely  <jwakely@redhat.com>
+
+	* testsuite/25_algorithms/make_heap/complexity.cc: Require effective
+	target for std::random_device.
+	* testsuite/26_numerics/random/random_device/cons/default.cc:
+	Likewise.
+	* testsuite/experimental/algorithm/sample-2.cc: Likewise.
+	* testsuite/experimental/algorithm/shuffle.cc: Likewise.
+	* testsuite/experimental/random/randint.cc: Likewise.
+	* testsuite/lib/libstdc++.exp
+	(check_effective_target_random_device): New proc.
+
 2018-07-04  Jonathan Wakely  <jwakely@redhat.com>
 	    Jakub Jelinek  <jakub@redhat.com>
 

libstdc++-v3/testsuite/25_algorithms/make_heap/complexity.cc

@@ -16,6 +16,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++11 } }
+// { dg-require-effective-target random_device }
 
 #include <random>
 #include <vector>

libstdc++-v3/testsuite/26_numerics/random/random_device/cons/default.cc

@@ -1,4 +1,5 @@
 // { dg-do run { target c++11 } }
+// { dg-require-effective-target random_device }
 // { dg-require-cstdint "" }
 //
 // 2008-11-24  Edward M. Smith-Rowland <3dw4rd@verizon.net>

libstdc++-v3/testsuite/experimental/algorithm/sample-2.cc

@@ -16,6 +16,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do run { target c++14 } }
+// { dg-require-effective-target random_device }
 // { dg-require-effective-target tls_runtime }
 // { dg-add-options tls }
 

libstdc++-v3/testsuite/experimental/algorithm/shuffle.cc

@@ -1,4 +1,5 @@
 // { dg-do run { target c++14 } }
+// { dg-require-effective-target random_device }
 // { dg-require-effective-target tls_runtime }
 // { dg-add-options tls }
 

libstdc++-v3/testsuite/experimental/random/randint.cc

@@ -1,4 +1,5 @@
 // { dg-do run { target c++14 } }
+// { dg-require-effective-target random_device }
 // { dg-require-effective-target tls_runtime }
 // { dg-add-options tls }
 

libstdc++-v3/testsuite/lib/libstdc++.exp

@@ -2061,6 +2061,34 @@ proc check_effective_target_cxx11-abi { } {
     return 0
 }
 
+# Return 1 if std::random_device should be usable using the current flags, 0 otherwise.
+proc check_effective_target_random_device { } {
+    global cxxflags
+
+    # Set up and preprocess a C++ test program that depends
+    # on std::random_device being usable.
+    set src random_device[pid].cc
+
+    set f [open $src "w"]
+    puts $f "#include <bits/c++config.h>"
+    puts $f "#if ! _GLIBCXX_USE_RANDOM_TR1"
+    puts $f "#  error No working std::random_device available"
+    puts $f "#endif"
+    close $f
+
+    set lines [v3_target_compile $src /dev/null preprocess ""]
+    file delete $src
+
+    if [string match "" $lines] {
+	# No error message, preprocessing succeeded.
+	verbose "check_v3_random_device: `1'" 2
+	return 1
+    }
+
+    verbose "check_v3_random_device: `0'" 2
+    return 0
+}
+
 set additional_prunes ""
 
 if { [info exists env(GCC_RUNTEST_PARALLELIZE_DIR)] \