[glibc] ldbl-128ibm-compat: workaround GCC 9 C++ PR90731

[glibc] ldbl-128ibm-compat: workaround GCC 9 C++ PR90731

[Paul E. Murphy]

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=86005fdbf40d6fc84d84c824d75c656e7c1398e3

commit 86005fdbf40d6fc84d84c824d75c656e7c1398e3
Author: Paul E. Murphy <murphyp@linux.vnet.ibm.com>
Date:   Fri Mar 6 09:41:03 2020 -0600

    ldbl-128ibm-compat: workaround GCC 9 C++ PR90731
    
    GCC 9 has a bug (PR90731) whereby __typeof does not correctly copy
    exception specifiers[1].  Surprisingly, this can be quieted by declaring
    "#pragma system_header", or if the headers are installed in a system
    directory.
    
    Work around this by using the pragma for any gcc version between
    9.0 and 9.2 to ensure tests continue to compile.
    
    [1] Example error from g++ 9.2.1:
    
    In file included from ../include/sys/cdefs.h:3,
                     from ../include/features.h:465,
                     from ../bits/libc-header-start.h:33,
                     from ../math/math.h:27,
                     from ../include/math.h:7,
                     from test-math-isinff.cc:21:
    ../libio/bits/stdio-ldbl.h:25:20: error: declaration of ‘int sprintf(char*, const char*, ...)’ has a different exception specifier
       25 | __LDBL_REDIR_DECL (sprintf)
          |                    ^~~~~~~
    ../misc/sys/cdefs.h:461:26: note: in definition of macro ‘__LDBL_REDIR_DECL’
      461 |   extern __typeof (name) name __asm (__ASMNAME ("__" #name "ieee128"));
          |                          ^~~~
    In file included from ../include/stdio.h:5,
                     from test-math-isinff.cc:22:
    ../libio/stdio.h:334:12: note: from previous declaration ‘int sprintf(char*, const char*, ...) throw ()’
      334 | extern int sprintf (char *__restrict __s,
          |            ^~~~~~~
    
    Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

Diff:
---
 include/monetary.h |  8 ++++++++
 include/printf.h   |  8 ++++++++
 include/stdio.h    | 10 ++++++++++
 include/stdlib.h   |  9 +++++++++
 include/wchar.h    |  9 +++++++++
 5 files changed, 44 insertions(+)

diff --git a/include/monetary.h b/include/monetary.h
index 240925e87d..bddc660ce2 100644
--- a/include/monetary.h
+++ b/include/monetary.h
@@ -1,3 +1,11 @@
+/* Workaround PR90731 with GCC 9 when using ldbl redirects in C++.  */
+#include <bits/floatn.h>
+#if defined __cplusplus && __LONG_DOUBLE_USES_FLOAT128 == 1
+# if __GNUC_PREREQ (9, 0) && !__GNUC_PREREQ (9, 3)
+#   pragma GCC system_header
+# endif
+#endif
+
 #include <stdlib/monetary.h>
 #ifndef _ISOMAC
 #include <stdarg.h>
diff --git a/include/printf.h b/include/printf.h
index d051514119..bdcfd29f63 100644
--- a/include/printf.h
+++ b/include/printf.h
@@ -1,5 +1,13 @@
 #ifndef	_PRINTF_H
 
+/* Workaround PR90731 with GCC 9 when using ldbl redirects in C++.  */
+#include <bits/floatn.h>
+#if defined __cplusplus && __LONG_DOUBLE_USES_FLOAT128 == 1
+# if __GNUC_PREREQ (9, 0) && !__GNUC_PREREQ (9, 3)
+#   pragma GCC system_header
+# endif
+#endif
+
 #include <stdio-common/printf.h>
 
 # ifndef _ISOMAC
diff --git a/include/stdio.h b/include/stdio.h
index 6718af4108..1c09daf13a 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -2,8 +2,18 @@
 # if !defined _ISOMAC && defined _IO_MTSAFE_IO
 #  include <stdio-lock.h>
 # endif
+
+/* Workaround PR90731 with GCC 9 when using ldbl redirects in C++.  */
+# include <bits/floatn.h>
+# if defined __cplusplus && __LONG_DOUBLE_USES_FLOAT128 == 1
+#  if __GNUC_PREREQ (9, 0) && !__GNUC_PREREQ (9, 3)
+#    pragma GCC system_header
+#  endif
+# endif
+
 # include <libio/stdio.h>
 # ifndef _ISOMAC
+
 #  define _LIBC_STDIO_H 1
 #  include <libio/libio.h>
 
diff --git a/include/stdlib.h b/include/stdlib.h
index 926f965f69..187a41e754 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -3,6 +3,15 @@
 #ifndef _ISOMAC
 # include <stddef.h>
 #endif
+
+/* Workaround PR90731 with GCC 9 when using ldbl redirects in C++.  */
+#include <bits/floatn.h>
+#if defined __cplusplus && __LONG_DOUBLE_USES_FLOAT128 == 1
+# if __GNUC_PREREQ (9, 0) && !__GNUC_PREREQ (9, 3)
+#   pragma GCC system_header
+# endif
+#endif
+
 #include <stdlib/stdlib.h>
 
 /* Now define the internal interfaces.  */
diff --git a/include/wchar.h b/include/wchar.h
index 617906eb14..bb49d844be 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -1,4 +1,13 @@
 #ifndef _WCHAR_H
+
+/* Workaround PR90731 with GCC 9 when using ldbl redirects in C++.  */
+# include <bits/floatn.h>
+# if defined __cplusplus && __LONG_DOUBLE_USES_FLOAT128 == 1
+#  if __GNUC_PREREQ (9, 0) && !__GNUC_PREREQ (9, 3)
+#   pragma GCC system_header
+#  endif
+# endif
+
 # include <wcsmbs/wchar.h>
 # ifndef _ISOMAC