test/hotspot/gtest/runtime/test_os.cpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */

 #include "precompiled.hpp"
 #include "memory/resourceArea.hpp"
 #include "runtime/os.hpp"
 #include "utilities/ostream.hpp"
 #include "unittest.hpp"

 static size_t small_page_size() {
   return os::vm_page_size();
 }

 static size_t large_page_size() {
   const size_t large_page_size_example = 4 * M;
   return os::page_size_for_region_aligned(large_page_size_example, 1);
 }

 TEST_VM(os, page_size_for_region) {
   size_t large_page_example = 4 * M;
   size_t large_page = os::page_size_for_region_aligned(large_page_example, 1);

   size_t small_page = os::vm_page_size();
   if (large_page > small_page) {
     size_t num_small_in_large = large_page / small_page;
     size_t page = os::page_size_for_region_aligned(large_page, num_small_in_large);
     ASSERT_EQ(page, small_page) << "Did not get a small page";
   }
 }

 TEST_VM(os, page_size_for_region_aligned) {
   if (UseLargePages) {
     const size_t small_page = small_page_size();
     const size_t large_page = large_page_size();

     if (large_page > small_page) {
       size_t num_small_pages_in_large = large_page / small_page;
       size_t page = os::page_size_for_region_aligned(large_page, num_small_pages_in_large);

       ASSERT_EQ(page, small_page);
     }
   }
 }

 TEST_VM(os, page_size_for_region_alignment) {
   if (UseLargePages) {
     const size_t small_page = small_page_size();
     const size_t large_page = large_page_size();
     if (large_page > small_page) {
       const size_t unaligned_region = large_page + 17;
       size_t page = os::page_size_for_region_aligned(unaligned_region, 1);
       ASSERT_EQ(page, small_page);

       const size_t num_pages = 5;
       const size_t aligned_region = large_page * num_pages;
       page = os::page_size_for_region_aligned(aligned_region, num_pages);
       ASSERT_EQ(page, large_page);
     }
   }
 }

 TEST_VM(os, page_size_for_region_unaligned) {
   if (UseLargePages) {
     // Given exact page size, should return that page size.
     for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
       size_t expected = os::_page_sizes[i];
       size_t actual = os::page_size_for_region_unaligned(expected, 1);
       ASSERT_EQ(expected, actual);
     }

     // Given slightly larger size than a page size, return the page size.
     for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
       size_t expected = os::_page_sizes[i];
       size_t actual = os::page_size_for_region_unaligned(expected + 17, 1);
       ASSERT_EQ(expected, actual);
     }

     // Given a slightly smaller size than a page size,
     // return the next smaller page size.
     if (os::_page_sizes[1] > os::_page_sizes[0]) {
       size_t expected = os::_page_sizes[0];
       size_t actual = os::page_size_for_region_unaligned(os::_page_sizes[1] - 17, 1);
       ASSERT_EQ(actual, expected);
     }

     // Return small page size for values less than a small page.
     size_t small_page = small_page_size();
     size_t actual = os::page_size_for_region_unaligned(small_page - 17, 1);
     ASSERT_EQ(small_page, actual);
   }
 }

 TEST(os, test_random) {
   const double m = 2147483647;
   double mean = 0.0, variance = 0.0, t;
   const int reps = 10000;
   unsigned int seed = 1;

   // tty->print_cr("seed %ld for %ld repeats...", seed, reps);
   os::init_random(seed);
   int num;
   for (int k = 0; k < reps; k++) {
     num = os::random();
     double u = (double)num / m;
     ASSERT_TRUE(u >= 0.0 && u <= 1.0) << "bad random number!";

     // calculate mean and variance of the random sequence
     mean += u;
     variance += (u*u);
   }
   mean /= reps;
   variance /= (reps - 1);

   ASSERT_EQ(num, 1043618065) << "bad seed";
   // tty->print_cr("mean of the 1st 10000 numbers: %f", mean);
   int intmean = mean*100;
   ASSERT_EQ(intmean, 50);
   // tty->print_cr("variance of the 1st 10000 numbers: %f", variance);
   int intvariance = variance*100;
   ASSERT_EQ(intvariance, 33);
   const double eps = 0.0001;
   t = fabsd(mean - 0.5018);
   ASSERT_LT(t, eps) << "bad mean";
   t = (variance - 0.3355) < 0.0 ? -(variance - 0.3355) : variance - 0.3355;
   ASSERT_LT(t, eps) << "bad variance";
 }


 #ifdef ASSERT
 TEST_VM_ASSERT_MSG(os, page_size_for_region_with_zero_min_pages, "sanity") {
   size_t region_size = 16 * os::vm_page_size();
   os::page_size_for_region_aligned(region_size, 0); // should assert
 }
 #endif

 static void do_test_print_hex_dump(address addr, size_t len, int unitsize, const char* expected) {
   char buf[256];
   buf[0] = '\0';
   stringStream ss(buf, sizeof(buf));
   os::print_hex_dump(&ss, addr, addr + len, unitsize);
 //  tty->print_cr("expected: %s", expected);
 //  tty->print_cr("result: %s", buf);
   ASSERT_NE(strstr(buf, expected), (char*)NULL);
 }

 TEST_VM(os, test_print_hex_dump) {
   const char* pattern [4] = {
 #ifdef VM_LITTLE_ENDIAN
     "00 01 02 03 04 05 06 07",
     "0100 0302 0504 0706",
     "03020100 07060504",
     "0706050403020100"
 #else
     "00 01 02 03 04 05 06 07",
     "0001 0203 0405 0607",
     "00010203 04050607",
     "0001020304050607"
 #endif
   };

   const char* pattern_not_readable [4] = {
     "?? ?? ?? ?? ?? ?? ?? ??",
     "???? ???? ???? ????",
     "???????? ????????",
     "????????????????"
   };

   // On AIX, zero page is readable.
   address unreadable =
 #ifdef AIX
     (address) 0xFFFFFFFFFFFF0000ULL;
 #else
     (address) 0
 #endif
     ;

   ResourceMark rm;
   char buf[64];
   stringStream ss(buf, sizeof(buf));
   outputStream* out = &ss;
 //  outputStream* out = tty; // enable for printout

   // Test dumping unreadable memory
   // Exclude test for Windows for now, since it needs SEH handling to work which cannot be
   // guaranteed when we call directly into VM code. (see JDK-8220220)
 #ifndef _WIN32
   do_test_print_hex_dump(unreadable, 100, 1, pattern_not_readable[0]);
   do_test_print_hex_dump(unreadable, 100, 2, pattern_not_readable[1]);
   do_test_print_hex_dump(unreadable, 100, 4, pattern_not_readable[2]);
   do_test_print_hex_dump(unreadable, 100, 8, pattern_not_readable[3]);
 #endif

   // Test dumping readable memory
   address arr = (address)os::malloc(100, mtInternal);
   for (int c = 0; c < 100; c++) {
     arr[c] = c;
   }

   // properly aligned
   do_test_print_hex_dump(arr, 100, 1, pattern[0]);
   do_test_print_hex_dump(arr, 100, 2, pattern[1]);
   do_test_print_hex_dump(arr, 100, 4, pattern[2]);
   do_test_print_hex_dump(arr, 100, 8, pattern[3]);

   // Not properly aligned. Should automatically down-align by unitsize
   do_test_print_hex_dump(arr + 1, 100, 2, pattern[1]);
   do_test_print_hex_dump(arr + 1, 100, 4, pattern[2]);
   do_test_print_hex_dump(arr + 1, 100, 8, pattern[3]);

   os::free(arr);
 }

 //////////////////////////////////////////////////////////////////////////////
 // Test os::vsnprintf and friends.

 static void check_snprintf_result(int expected, size_t limit, int actual, bool expect_count) {
   if (expect_count || ((size_t)expected < limit)) {
     ASSERT_EQ(expected, actual);
   } else {
     ASSERT_GT(0, actual);
   }
 }

 // PrintFn is expected to be int (*)(char*, size_t, const char*, ...).
 // But jio_snprintf is a C-linkage function with that signature, which
 // has a different type on some platforms (like Solaris).
 template<typename PrintFn>
 static void test_snprintf(PrintFn pf, bool expect_count) {
   const char expected[] = "abcdefghijklmnopqrstuvwxyz";
   const int expected_len = sizeof(expected) - 1;
   const size_t padding_size = 10;
   char buffer[2 * (sizeof(expected) + padding_size)];
   char check_buffer[sizeof(buffer)];
   const char check_char = '1';  // Something not in expected.
   memset(check_buffer, check_char, sizeof(check_buffer));
   const size_t sizes_to_test[] = {
     sizeof(buffer) - padding_size,       // Fits, with plenty of space to spare.
     sizeof(buffer)/2,                    // Fits, with space to spare.
     sizeof(buffer)/4,                    // Doesn't fit.
     sizeof(expected) + padding_size + 1, // Fits, with a little room to spare
     sizeof(expected) + padding_size,     // Fits exactly.
     sizeof(expected) + padding_size - 1, // Doesn't quite fit.
     2,                                   // One char + terminating NUL.
     1,                                   // Only space for terminating NUL.
     0 };                                 // No space at all.
   for (unsigned i = 0; i < ARRAY_SIZE(sizes_to_test); ++i) {
     memset(buffer, check_char, sizeof(buffer)); // To catch stray writes.
     size_t test_size = sizes_to_test[i];
     ResourceMark rm;
     stringStream s;
     s.print("test_size: " SIZE_FORMAT, test_size);
     SCOPED_TRACE(s.as_string());
     size_t prefix_size = padding_size;
     guarantee(test_size <= (sizeof(buffer) - prefix_size), "invariant");
     size_t write_size = MIN2(sizeof(expected), test_size);
     size_t suffix_size = sizeof(buffer) - prefix_size - write_size;
     char* write_start = buffer + prefix_size;
     char* write_end = write_start + write_size;

     int result = pf(write_start, test_size, "%s", expected);

     check_snprintf_result(expected_len, test_size, result, expect_count);

     // Verify expected output.
     if (test_size > 0) {
       ASSERT_EQ(0, strncmp(write_start, expected, write_size - 1));
       // Verify terminating NUL of output.
       ASSERT_EQ('\0', write_start[write_size - 1]);
     } else {
       guarantee(test_size == 0, "invariant");
       guarantee(write_size == 0, "invariant");
       guarantee(prefix_size + suffix_size == sizeof(buffer), "invariant");
       guarantee(write_start == write_end, "invariant");
     }

     // Verify no scribbling on prefix or suffix.
     ASSERT_EQ(0, strncmp(buffer, check_buffer, prefix_size));
     ASSERT_EQ(0, strncmp(write_end, check_buffer, suffix_size));
   }

   // Special case of 0-length buffer with empty (except for terminator) output.
   check_snprintf_result(0, 0, pf(NULL, 0, "%s", ""), expect_count);
   check_snprintf_result(0, 0, pf(NULL, 0, ""), expect_count);
 }

 // This is probably equivalent to os::snprintf, but we're being
 // explicit about what we're testing here.
 static int vsnprintf_wrapper(char* buf, size_t len, const char* fmt, ...) {
   va_list args;
   va_start(args, fmt);
   int result = os::vsnprintf(buf, len, fmt, args);
   va_end(args);
   return result;
 }

 TEST_VM(os, vsnprintf) {
   test_snprintf(vsnprintf_wrapper, true);
 }

 TEST_VM(os, snprintf) {
   test_snprintf(os::snprintf, true);
 }

 // These are declared in jvm.h; test here, with related functions.
 extern "C" {
 int jio_vsnprintf(char*, size_t, const char*, va_list);
 int jio_snprintf(char*, size_t, const char*, ...);
 }

 // This is probably equivalent to jio_snprintf, but we're being
 // explicit about what we're testing here.
 static int jio_vsnprintf_wrapper(char* buf, size_t len, const char* fmt, ...) {
   va_list args;
   va_start(args, fmt);
   int result = jio_vsnprintf(buf, len, fmt, args);
   va_end(args);
   return result;
 }

 TEST_VM(os, jio_vsnprintf) {
   test_snprintf(jio_vsnprintf_wrapper, false);
 }

 TEST_VM(os, jio_snprintf) {
   test_snprintf(jio_snprintf, false);
 }
	/*
	* Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	#include "precompiled.hpp"
	#include "memory/resourceArea.hpp"
	#include "runtime/os.hpp"
	#include "utilities/ostream.hpp"
	#include "unittest.hpp"

	static size_t small_page_size() {
	return os::vm_page_size();
	}

	static size_t large_page_size() {
	const size_t large_page_size_example = 4 * M;
	return os::page_size_for_region_aligned(large_page_size_example, 1);
	}

	TEST_VM(os, page_size_for_region) {
	size_t large_page_example = 4 * M;
	size_t large_page = os::page_size_for_region_aligned(large_page_example, 1);

	size_t small_page = os::vm_page_size();
	if (large_page > small_page) {
	size_t num_small_in_large = large_page / small_page;
	size_t page = os::page_size_for_region_aligned(large_page, num_small_in_large);
	ASSERT_EQ(page, small_page) << "Did not get a small page";
	}
	}

	TEST_VM(os, page_size_for_region_aligned) {
	if (UseLargePages) {
	const size_t small_page = small_page_size();
	const size_t large_page = large_page_size();

	if (large_page > small_page) {
	size_t num_small_pages_in_large = large_page / small_page;
	size_t page = os::page_size_for_region_aligned(large_page, num_small_pages_in_large);

	ASSERT_EQ(page, small_page);
	}
	}
	}

	TEST_VM(os, page_size_for_region_alignment) {
	if (UseLargePages) {
	const size_t small_page = small_page_size();
	const size_t large_page = large_page_size();
	if (large_page > small_page) {
	const size_t unaligned_region = large_page + 17;
	size_t page = os::page_size_for_region_aligned(unaligned_region, 1);
	ASSERT_EQ(page, small_page);

	const size_t num_pages = 5;
	const size_t aligned_region = large_page * num_pages;
	page = os::page_size_for_region_aligned(aligned_region, num_pages);
	ASSERT_EQ(page, large_page);
	}
	}
	}

	TEST_VM(os, page_size_for_region_unaligned) {
	if (UseLargePages) {
	// Given exact page size, should return that page size.
	for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
	size_t expected = os::_page_sizes[i];
	size_t actual = os::page_size_for_region_unaligned(expected, 1);
	ASSERT_EQ(expected, actual);
	}

	// Given slightly larger size than a page size, return the page size.
	for (size_t i = 0; os::_page_sizes[i] != 0; i++) {
	size_t expected = os::_page_sizes[i];
	size_t actual = os::page_size_for_region_unaligned(expected + 17, 1);
	ASSERT_EQ(expected, actual);
	}

	// Given a slightly smaller size than a page size,
	// return the next smaller page size.
	if (os::_page_sizes[1] > os::_page_sizes[0]) {
	size_t expected = os::_page_sizes[0];
	size_t actual = os::page_size_for_region_unaligned(os::_page_sizes[1] - 17, 1);
	ASSERT_EQ(actual, expected);
	}

	// Return small page size for values less than a small page.
	size_t small_page = small_page_size();
	size_t actual = os::page_size_for_region_unaligned(small_page - 17, 1);
	ASSERT_EQ(small_page, actual);
	}
	}

	TEST(os, test_random) {
	const double m = 2147483647;
	double mean = 0.0, variance = 0.0, t;
	const int reps = 10000;
	unsigned int seed = 1;

	// tty->print_cr("seed %ld for %ld repeats...", seed, reps);
	os::init_random(seed);
	int num;
	for (int k = 0; k < reps; k++) {
	num = os::random();
	double u = (double)num / m;
	ASSERT_TRUE(u >= 0.0 && u <= 1.0) << "bad random number!";

	// calculate mean and variance of the random sequence
	mean += u;
	variance += (u*u);
	}
	mean /= reps;
	variance /= (reps - 1);

	ASSERT_EQ(num, 1043618065) << "bad seed";
	// tty->print_cr("mean of the 1st 10000 numbers: %f", mean);
	int intmean = mean*100;
	ASSERT_EQ(intmean, 50);
	// tty->print_cr("variance of the 1st 10000 numbers: %f", variance);
	int intvariance = variance*100;
	ASSERT_EQ(intvariance, 33);
	const double eps = 0.0001;
	t = fabsd(mean - 0.5018);
	ASSERT_LT(t, eps) << "bad mean";
	t = (variance - 0.3355) < 0.0 ? -(variance - 0.3355) : variance - 0.3355;
	ASSERT_LT(t, eps) << "bad variance";
	}


	#ifdef ASSERT
	TEST_VM_ASSERT_MSG(os, page_size_for_region_with_zero_min_pages, "sanity") {
	size_t region_size = 16 * os::vm_page_size();
	os::page_size_for_region_aligned(region_size, 0); // should assert
	}
	#endif

	static void do_test_print_hex_dump(address addr, size_t len, int unitsize, const char* expected) {
	char buf[256];
	buf[0] = '\0';
	stringStream ss(buf, sizeof(buf));
	os::print_hex_dump(&ss, addr, addr + len, unitsize);
	// tty->print_cr("expected: %s", expected);
	// tty->print_cr("result: %s", buf);
	ASSERT_NE(strstr(buf, expected), (char*)NULL);
	}

	TEST_VM(os, test_print_hex_dump) {
	const char* pattern [4] = {
	#ifdef VM_LITTLE_ENDIAN
	"00 01 02 03 04 05 06 07",
	"0100 0302 0504 0706",
	"03020100 07060504",
	"0706050403020100"
	#else
	"00 01 02 03 04 05 06 07",
	"0001 0203 0405 0607",
	"00010203 04050607",
	"0001020304050607"
	#endif
	};

	const char* pattern_not_readable [4] = {
	"?? ?? ?? ?? ?? ?? ?? ??",
	"???? ???? ???? ????",
	"???????? ????????",
	"????????????????"
	};

	// On AIX, zero page is readable.
	address unreadable =
	#ifdef AIX
	(address) 0xFFFFFFFFFFFF0000ULL;
	#else
	(address) 0
	#endif
	;

	ResourceMark rm;
	char buf[64];
	stringStream ss(buf, sizeof(buf));
	outputStream* out = &ss;
	// outputStream* out = tty; // enable for printout

	// Test dumping unreadable memory
	// Exclude test for Windows for now, since it needs SEH handling to work which cannot be
	// guaranteed when we call directly into VM code. (see JDK-8220220)
	#ifndef _WIN32
	do_test_print_hex_dump(unreadable, 100, 1, pattern_not_readable[0]);
	do_test_print_hex_dump(unreadable, 100, 2, pattern_not_readable[1]);
	do_test_print_hex_dump(unreadable, 100, 4, pattern_not_readable[2]);
	do_test_print_hex_dump(unreadable, 100, 8, pattern_not_readable[3]);
	#endif

	// Test dumping readable memory
	address arr = (address)os::malloc(100, mtInternal);
	for (int c = 0; c < 100; c++) {
	arr[c] = c;
	}

	// properly aligned
	do_test_print_hex_dump(arr, 100, 1, pattern[0]);
	do_test_print_hex_dump(arr, 100, 2, pattern[1]);
	do_test_print_hex_dump(arr, 100, 4, pattern[2]);
	do_test_print_hex_dump(arr, 100, 8, pattern[3]);

	// Not properly aligned. Should automatically down-align by unitsize
	do_test_print_hex_dump(arr + 1, 100, 2, pattern[1]);
	do_test_print_hex_dump(arr + 1, 100, 4, pattern[2]);
	do_test_print_hex_dump(arr + 1, 100, 8, pattern[3]);

	os::free(arr);
	}

	//////////////////////////////////////////////////////////////////////////////
	// Test os::vsnprintf and friends.

	static void check_snprintf_result(int expected, size_t limit, int actual, bool expect_count) {
	if (expect_count \|\| ((size_t)expected < limit)) {
	ASSERT_EQ(expected, actual);
	} else {
	ASSERT_GT(0, actual);
	}
	}

	// PrintFn is expected to be int ()(char, size_t, const char*, ...).
	// But jio_snprintf is a C-linkage function with that signature, which
	// has a different type on some platforms (like Solaris).
	template<typename PrintFn>
	static void test_snprintf(PrintFn pf, bool expect_count) {
	const char expected[] = "abcdefghijklmnopqrstuvwxyz";
	const int expected_len = sizeof(expected) - 1;
	const size_t padding_size = 10;
	char buffer[2 * (sizeof(expected) + padding_size)];
	char check_buffer[sizeof(buffer)];
	const char check_char = '1'; // Something not in expected.
	memset(check_buffer, check_char, sizeof(check_buffer));
	const size_t sizes_to_test[] = {
	sizeof(buffer) - padding_size, // Fits, with plenty of space to spare.
	sizeof(buffer)/2, // Fits, with space to spare.
	sizeof(buffer)/4, // Doesn't fit.
	sizeof(expected) + padding_size + 1, // Fits, with a little room to spare
	sizeof(expected) + padding_size, // Fits exactly.
	sizeof(expected) + padding_size - 1, // Doesn't quite fit.
	2, // One char + terminating NUL.
	1, // Only space for terminating NUL.
	0 }; // No space at all.
	for (unsigned i = 0; i < ARRAY_SIZE(sizes_to_test); ++i) {
	memset(buffer, check_char, sizeof(buffer)); // To catch stray writes.
	size_t test_size = sizes_to_test[i];
	ResourceMark rm;
	stringStream s;
	s.print("test_size: " SIZE_FORMAT, test_size);
	SCOPED_TRACE(s.as_string());
	size_t prefix_size = padding_size;
	guarantee(test_size <= (sizeof(buffer) - prefix_size), "invariant");
	size_t write_size = MIN2(sizeof(expected), test_size);
	size_t suffix_size = sizeof(buffer) - prefix_size - write_size;
	char* write_start = buffer + prefix_size;
	char* write_end = write_start + write_size;

	int result = pf(write_start, test_size, "%s", expected);

	check_snprintf_result(expected_len, test_size, result, expect_count);

	// Verify expected output.
	if (test_size > 0) {
	ASSERT_EQ(0, strncmp(write_start, expected, write_size - 1));
	// Verify terminating NUL of output.
	ASSERT_EQ('\0', write_start[write_size - 1]);
	} else {
	guarantee(test_size == 0, "invariant");
	guarantee(write_size == 0, "invariant");
	guarantee(prefix_size + suffix_size == sizeof(buffer), "invariant");
	guarantee(write_start == write_end, "invariant");
	}

	// Verify no scribbling on prefix or suffix.
	ASSERT_EQ(0, strncmp(buffer, check_buffer, prefix_size));
	ASSERT_EQ(0, strncmp(write_end, check_buffer, suffix_size));
	}

	// Special case of 0-length buffer with empty (except for terminator) output.
	check_snprintf_result(0, 0, pf(NULL, 0, "%s", ""), expect_count);
	check_snprintf_result(0, 0, pf(NULL, 0, ""), expect_count);
	}

	// This is probably equivalent to os::snprintf, but we're being
	// explicit about what we're testing here.
	static int vsnprintf_wrapper(char* buf, size_t len, const char* fmt, ...) {
	va_list args;
	va_start(args, fmt);
	int result = os::vsnprintf(buf, len, fmt, args);
	va_end(args);
	return result;
	}

	TEST_VM(os, vsnprintf) {
	test_snprintf(vsnprintf_wrapper, true);
	}

	TEST_VM(os, snprintf) {
	test_snprintf(os::snprintf, true);
	}

	// These are declared in jvm.h; test here, with related functions.
	extern "C" {
	int jio_vsnprintf(char, size_t, const char, va_list);
	int jio_snprintf(char, size_t, const char, ...);
	}

	// This is probably equivalent to jio_snprintf, but we're being
	// explicit about what we're testing here.
	static int jio_vsnprintf_wrapper(char* buf, size_t len, const char* fmt, ...) {
	va_list args;
	va_start(args, fmt);
	int result = jio_vsnprintf(buf, len, fmt, args);
	va_end(args);
	return result;
	}

	TEST_VM(os, jio_vsnprintf) {
	test_snprintf(jio_vsnprintf_wrapper, false);
	}

	TEST_VM(os, jio_snprintf) {
	test_snprintf(jio_snprintf, false);
	}