[PATCH] PR libstdc++/68737 Do not use vsnprintf on HPUX

[Jonathan Wakely]

It doesn't conform to the spec, so use vsprintf with a large buffer
instead.

        PR libstdc++/68737
        * config/locale/generic/c_locale.h (__convert_from_v)
        [_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
        * config/os/hpux/os_defines.h: Define _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
        * include/bits/locale_facets.tcc (num_put::_M_insert_float)
        [_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.

Tested powerpc64le-linux, committed to trunk.


commit f69cc2009670cea920dba01b0588f778a347e180
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Mon Jan 28 23:34:32 2019 +0000

    PR libstdc++/68737 Do not use vsnprintf on HPUX
    
    It doesn't conform to the spec, so use vsprintf with a large buffer
    instead.
    
            PR libstdc++/68737
            * config/locale/generic/c_locale.h (__convert_from_v)
            [_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.
            * config/os/hpux/os_defines.h: Define 
_GLIBCXX_HAVE_BROKEN_VSNPRINTF.
            * include/bits/locale_facets.tcc (num_put::_M_insert_float)
            [_GLIBCXX_USE_C99_STDIO]: Also check _GLIBCXX_HAVE_BROKEN_VSNPRINTF.

diff --git a/libstdc++-v3/config/locale/generic/c_locale.h 
b/libstdc++-v3/config/locale/generic/c_locale.h
index 3b95a43160e..625a61c8bb2 100644
--- a/libstdc++-v3/config/locale/generic/c_locale.h
+++ b/libstdc++-v3/config/locale/generic/c_locale.h
@@ -70,7 +70,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     __builtin_va_list __args;
     __builtin_va_start(__args, __fmt);
 
-#if _GLIBCXX_USE_C99_STDIO
+#if _GLIBCXX_USE_C99_STDIO && !_GLIBCXX_HAVE_BROKEN_VSNPRINTF
     const int __ret = __builtin_vsnprintf(__out, __size, __fmt, __args);
 #else
     const int __ret = __builtin_vsprintf(__out, __fmt, __args);
diff --git a/libstdc++-v3/config/os/hpux/os_defines.h 
b/libstdc++-v3/config/os/hpux/os_defines.h
index 04834b0cd0c..20a8b3ed30b 100644
--- a/libstdc++-v3/config/os/hpux/os_defines.h
+++ b/libstdc++-v3/config/os/hpux/os_defines.h
@@ -109,4 +109,9 @@ typedef long int __padding_type;
 #if defined (__hppa__)
 #define _GLIBCXX_HAVE_BROKEN_STRTOLD 1
 #endif
+
+// The vnsprintf function returns -1 when the buffer is too small.
+// See PR libstdc++/68737.
+#define _GLIBCXX_HAVE_BROKEN_VSNPRINTF 1
+
 #endif
diff --git a/libstdc++-v3/include/bits/locale_facets.tcc 
b/libstdc++-v3/include/bits/locale_facets.tcc
index c387fdfdbfb..2eb8167db9a 100644
--- a/libstdc++-v3/include/bits/locale_facets.tcc
+++ b/libstdc++-v3/include/bits/locale_facets.tcc
@@ -992,7 +992,7 @@ _GLIBCXX_BEGIN_NAMESPACE_LDBL
        char __fbuf[16];
        __num_base::_S_format_float(__io, __fbuf, __mod);
 
-#if _GLIBCXX_USE_C99_STDIO
+#if _GLIBCXX_USE_C99_STDIO && !_GLIBCXX_HAVE_BROKEN_VSNPRINTF
        // Precision is always used except for hexfloat format.
        const bool __use_prec =
          (__io.flags() & ios_base::floatfield) != ios_base::floatfield;