Do not redirect calls to __GI_* symbols, when redirecting to *ieee128

On platforms where long double has IEEE binary128 format as a third
option (initially, only powerpc64le), many exported functions are
redirected to their __*ieee128 equivalents.  This redirection is
provided by installed headers such as stdio-ldbl.h, and is supposed to
work correctly with user code.

However, during the build of glibc, similar redirections are employed,
in internal headers, such as include/stdio.h, in order to avoid extra
PLT entries.  These redirections conflict with the redirections to
__*ieee128, and must be avoided during the build.  This patch protects
the second redirections with a test for __LONG_DOUBLE_USES_FLOAT128, a
new macro that is defined to 1 when functions that deal with long double
typed values reuses the _Float128 implementation (this is currently only
true for powerpc64le).

Tested for powerpc64le, x86_64, and with build-many-glibcs.py.

Co-authored-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

bits/long-double.h

@@ -37,3 +37,4 @@
 #ifndef __NO_LONG_DOUBLE_MATH
 # define __NO_LONG_DOUBLE_MATH	1
 #endif
+#define __LONG_DOUBLE_USES_FLOAT128 0

include/stdio.h

@@ -13,7 +13,9 @@ extern int __fcloseall (void) attribute_hidden;
 extern int __snprintf (char *__restrict __s, size_t __maxlen,
 		       const char *__restrict __format, ...)
      __attribute__ ((__format__ (__printf__, 3, 4)));
+#  if __LONG_DOUBLE_USES_FLOAT128 == 0
 libc_hidden_proto (__snprintf)
+#  endif
 extern int __vfscanf (FILE *__restrict __s,
 		      const char *__restrict __format,
 		      __gnuc_va_list __arg)
@@ -72,7 +74,8 @@ libc_hidden_proto (__isoc99_vfscanf)
    Unfortunately, symbol redirection is not transitive, so the
    __REDIRECT in the public header does not link up with the above
    libc_hidden_proto.  Bridge the gap with a macro.  */
-#  if !__GLIBC_USE (DEPRECATED_SCANF)
+#  if !__GLIBC_USE (DEPRECATED_SCANF) \
+      && __LONG_DOUBLE_USES_FLOAT128 == 0
 #   undef sscanf
 #   define sscanf __isoc99_sscanf
 #  endif
@@ -150,7 +153,9 @@ libc_hidden_proto (__libc_readline_unlocked);
 extern const char *const _sys_errlist_internal[] attribute_hidden;
 extern int _sys_nerr_internal attribute_hidden;
 
+#if __LONG_DOUBLE_USES_FLOAT128 == 0
 libc_hidden_proto (__asprintf)
+#endif
 #  if IS_IN (libc)
 extern FILE *_IO_new_fopen (const char*, const char*);
 #   define fopen(fname, mode) _IO_new_fopen (fname, mode)
@@ -171,13 +176,15 @@ extern int _IO_new_fgetpos (FILE *, __fpos_t *);
 #   define fgetpos(fp, posp) _IO_new_fgetpos (fp, posp)
 #  endif
 
-libc_hidden_proto (dprintf)
 extern __typeof (dprintf) __dprintf
      __attribute__ ((__format__ (__printf__, 2, 3)));
 libc_hidden_proto (__dprintf)
+#if __LONG_DOUBLE_USES_FLOAT128 == 0
+libc_hidden_proto (dprintf)
 libc_hidden_proto (fprintf)
 libc_hidden_proto (vfprintf)
 libc_hidden_proto (sprintf)
+#endif
 libc_hidden_proto (fwrite)
 libc_hidden_proto (perror)
 libc_hidden_proto (remove)

include/stdlib.h

@@ -202,9 +202,12 @@ libc_hidden_proto (____strtoll_l_internal)
 libc_hidden_proto (____strtoul_l_internal)
 libc_hidden_proto (____strtoull_l_internal)
 
+#include <bits/floatn.h>
 libc_hidden_proto (strtof)
 libc_hidden_proto (strtod)
+#if __LONG_DOUBLE_USES_FLOAT128 == 0
 libc_hidden_proto (strtold)
+#endif
 libc_hidden_proto (strtol)
 libc_hidden_proto (strtoll)
 libc_hidden_proto (strtoul)

sysdeps/ieee754/ldbl-128/bits/long-double.h

@@ -18,3 +18,4 @@
 
 /* long double is distinct from double, so there is nothing to
    define here.  */
+#define __LONG_DOUBLE_USES_FLOAT128 0

sysdeps/ieee754/ldbl-128ibm-compat/bits/long-double.h

@@ -0,0 +1,29 @@
+/* Properties of long double type.  ldbl-opt version.
+   Copyright (C) 2019 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  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/>.  */
+
+#ifndef __NO_LONG_DOUBLE_MATH
+# define __LONG_DOUBLE_MATH_OPTIONAL	1
+# ifndef __LONG_DOUBLE_128__
+#  define __NO_LONG_DOUBLE_MATH		1
+# endif
+#endif
+/* On platforms that reuse the _Float128 implementation for IEEE long
+   double, access to the correct long double functions is selected based
+   on the long double mode being used during the compilation.  On
+   powerpc64le, this is true when -mabi=ieeelongdouble is in use.  */
+#define __LONG_DOUBLE_USES_FLOAT128 (__LDBL_MANT_DIG__ == 113)

sysdeps/ieee754/ldbl-96/bits/long-double.h

@@ -18,3 +18,4 @@
 
 /* long double is distinct from double, so there is nothing to
    define here.  */
+#define __LONG_DOUBLE_USES_FLOAT128 0

sysdeps/ieee754/ldbl-opt/bits/long-double.h

@@ -22,3 +22,4 @@
 #  define __NO_LONG_DOUBLE_MATH		1
 # endif
 #endif
+#define __LONG_DOUBLE_USES_FLOAT128 0

sysdeps/mips/ieee754/bits/long-double.h

@@ -21,3 +21,4 @@
 #if !defined __NO_LONG_DOUBLE_MATH && _MIPS_SIM == _ABIO32
 # define __NO_LONG_DOUBLE_MATH	1
 #endif
+#define __LONG_DOUBLE_USES_FLOAT128 0

sysdeps/unix/sysv/linux/sparc/sparc32/bits/long-double.h

@@ -24,3 +24,4 @@
 #  define __NO_LONG_DOUBLE_MATH        1
 # endif
 #endif
+#define __LONG_DOUBLE_USES_FLOAT128 0

sysdeps/unix/sysv/linux/sparc/sparc64/bits/long-double.h

@@ -24,3 +24,4 @@
 #  define __NO_LONG_DOUBLE_MATH        1
 # endif
 #endif
+#define __LONG_DOUBLE_USES_FLOAT128 0