ldbl-128ibm-compat: Add printf_size

Since the addition of the _Float128 API, strfromf128 and printf_size use
__printf_fp to print _Float128 values.  This is achieved by setting the
'is_binary128' member of the 'printf_info' structure to one.  Now that
the format of long double on powerpc64le is getting a third option, this
mechanism is reused for long double values that have binary128 format
(i.e.: when -mabi=ieeelongdouble).

This patch adds __printf_sizeieee128 as an exported symbol, but doesn't
provide redirections from printf_size, yet.  All redirections will be
installed in a future commit, once all other functions that print or
read long double values with binary128 format are ready.  In
__printf_fp, when 'is_binary128' is one, the floating-point argument is
treated as if it was of _Float128 type, regardless of the value of
'is_long_double', thus __printf_sizeieee128 sets 'is_binary128' to the
same value of 'is_long_double'.  Otherwise, double values would not be
printed correctly.

Tested for powerpc64le.

1 files changed, 51 insertions, 0 deletions

diff --git a/stdio-common/tst-printfsz-islongdouble.c b/stdio-common/tst-printfsz-islongdouble.c
new file mode 100644
index 0000000000..a6a534bb3d
--- /dev/null
+++ b/stdio-common/tst-printfsz-islongdouble.c
@@ -0,0 +1,51 @@
+/* Test for the behaviour of 'is_long_double' in printf_size.
+   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 <printf.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <support/check.h>
+
+static int
+do_test (void)
+{
+  double d = 2000;
+  double *dptr = &d;
+  long double ld = 4000;
+  long double *ldptr = & ld;
+  struct printf_info info;
+
+  memset (&info, 0, sizeof (info));
+  info.spec = L'f';
+
+  /* Print a value with double type.  */
+  printf_size (stdout, &info, (void *) &dptr);
+
+  /* Printf a value with long double type.  */
+  info.is_long_double = 1;
+  printf_size (stdout, &info, (void *) &ldptr);
+
+  /* Setting both 'is_long_double' and 'is_binary128' to one is out of
+     the scope of this test, because such configuration is only valid
+     when _Float128 and long double are ABI-distinct (which is not
+     always true in this arch-independent test).  */
+  return 0;
+}
+
+#include <support/test-driver.c>