stdlib/test-bz22786: Avoid spurious test failures using alias mappings

On systems without enough random-access memory, stdlib/test-bz22786
will go deeply into swap and time out, even with a substantial
TIMEOUTFACTOR.  This commit adds a facility to construct repeating
strings with alias mappings, so that the requirement for physical
memory, and uses it in stdlib/test-bz22786.

1 files changed, 85 insertions, 0 deletions

diff --git a/support/tst-support_blob_repeat.c b/support/tst-support_blob_repeat.c
new file mode 100644
index 0000000000..1978c14488
--- /dev/null
+++ b/support/tst-support_blob_repeat.c
@@ -0,0 +1,85 @@
+/* Tests for <support/blob_repeat.h>
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <support/blob_repeat.h>
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  struct support_blob_repeat repeat
+    = support_blob_repeat_allocate ("5", 1, 5);
+  TEST_COMPARE_BLOB (repeat.start, repeat.size, "55555", 5);
+  support_blob_repeat_free (&repeat);
+
+  repeat = support_blob_repeat_allocate ("ABC", 3, 3);
+  TEST_COMPARE_BLOB (repeat.start, repeat.size, "ABCABCABC", 9);
+  support_blob_repeat_free (&repeat);
+
+  repeat = support_blob_repeat_allocate ("abc", 4, 3);
+  TEST_COMPARE_BLOB (repeat.start, repeat.size, "abc\0abc\0abc", 12);
+  support_blob_repeat_free (&repeat);
+
+  size_t gigabyte = 1U << 30;
+  repeat = support_blob_repeat_allocate ("X", 1, gigabyte + 1);
+  if (repeat.start == NULL)
+    puts ("warning: not enough memory for 1 GiB mapping");
+  else
+    {
+      TEST_COMPARE (repeat.size, gigabyte + 1);
+      {
+        unsigned char *p = repeat.start;
+        for (size_t i = 0; i < gigabyte + 1; ++i)
+          if (p[i] != 'X')
+            FAIL_EXIT1 ("invalid byte 0x%02x at %zu", p[i], i);
+
+        /* Check that there is no sharing across the mapping.  */
+        p[0] = 'Y';
+        p[1U << 24] = 'Z';
+        for (size_t i = 0; i < gigabyte + 1; ++i)
+          if (i == 0)
+            TEST_COMPARE (p[i], 'Y');
+          else if (i == 1U << 24)
+            TEST_COMPARE (p[i], 'Z');
+          else if (p[i] != 'X')
+            FAIL_EXIT1 ("invalid byte 0x%02x at %zu", p[i], i);
+      }
+    }
+  support_blob_repeat_free (&repeat);
+
+  repeat = support_blob_repeat_allocate ("012345678", 9, 10 * 1000 * 1000);
+  if (repeat.start == NULL)
+    puts ("warning: not enough memory for large mapping");
+  else
+    {
+      unsigned char *p = repeat.start;
+      for (int i = 0; i < 10 * 1000 * 1000; ++i)
+        for (int j = 0; j <= 8; ++j)
+          if (p[i * 9 + j] != '0' + j)
+            {
+              printf ("error: element %d index %d\n", i, j);
+              TEST_COMPARE (p[i * 9 + j], '0' + j);
+            }
+    }
+  support_blob_repeat_free (&repeat);
+
+  return 0;
+}
+
+#include <support/test-driver.c>