elf: add test for dl-printf

This patch checks _dl_debug_vdprintf, by passing various inputs to
_dl_dprintf and comparing the output with invocations of snprintf.

Signed-off-by: Roy Eldar <royeldar0@gmail.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

elf/Makefile

@@ -275,6 +275,7 @@ tests-static-normal := \
 
 tests-static-internal := \
   tst-dl_find_object-static \
+  tst-dl-printf-static \
   tst-ptrguard1-static \
   tst-stackguard1-static \
   tst-tls1-static \

elf/tst-dl-printf-static.c

@@ -0,0 +1,78 @@
+/* Check _dl_debug_vdprintf.
+   Copyright The GNU Toolchain Authors.
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+
+#define BUFSZ 64
+
+#define TEST(fmt, ...)                                                        \
+  do                                                                          \
+    {                                                                         \
+      char str1[BUFSZ], str2[BUFSZ];                                          \
+      int len1 = snprintf (str1, BUFSZ, fmt, __VA_ARGS__);                    \
+      TEST_VERIFY_EXIT (len1 >= 0);                                           \
+      TEST_VERIFY_EXIT (len1 < BUFSZ);                                        \
+      _dl_dprintf (fds[1], fmt, __VA_ARGS__);                                 \
+      ssize_t len2 = read (fds[0], str2, BUFSZ);                              \
+      TEST_VERIFY_EXIT (len2 >= 0);                                           \
+      TEST_VERIFY_EXIT (len2 < BUFSZ);                                        \
+      str2[len2] = '\0';                                                      \
+      TEST_COMPARE_STRING (str1, str2);                                       \
+    }                                                                         \
+  while (0)
+
+static int
+do_test (void)
+{
+  int fds[2];
+  xpipe (fds);
+  TEST ("%d", 0);
+  TEST ("%d", 1);
+  TEST ("%d", INT_MAX);
+  TEST ("%d", -1);
+  TEST ("%d", INT_MIN + 1);
+  TEST ("%d", INT_MIN);
+  TEST ("%u", 0U);
+  TEST ("%u", 1U);
+  TEST ("%u", UINT_MAX);
+  TEST ("%x", 0);
+  TEST ("%x", 1);
+  TEST ("%x", UINT_MAX);
+  TEST ("%ld", 0L);
+  TEST ("%ld", 1L);
+  TEST ("%ld", LONG_MAX);
+  TEST ("%ld", -1L);
+  TEST ("%ld", LONG_MIN + 1);
+  TEST ("%ld", LONG_MIN);
+  TEST ("%lu", 0UL);
+  TEST ("%lu", 1UL);
+  TEST ("%lu", ULONG_MAX);
+  TEST ("%lx", 0UL);
+  TEST ("%lx", 1UL);
+  TEST ("%lx", ULONG_MAX);
+  xclose (fds[0]);
+  xclose (fds[1]);
+  return 0;
+}
+
+#include <support/test-driver.c>