Poor me... (was: Re: [PATCH, RFA] Reworked fix for PR4402)

[Paolo Carlini <pcarlini at unitus dot it>]

Well...

of course there is *no* grouping at all for float types... (see, f.i., Langer/Kreft 571-572).
May I say that I have been a little bit sidetracked by the comment at the beginning of
_M_widen_float?

So my previous patches were conceptually wrong :( Pragmatically, there was a factor of 4/3
(2), completely unmotivated in the __builtin_alloca call in _M_widen_float.

Anyway, the present proposal, which seems ok to me, shows also an hunk for _M_insert, which
in fact also had (as _M_widen_float and _M_convert_float did) an hardwired 64 in the
__builtin_alloca call (why testing did'nt reveal that?).

This time too, tested i686-pc-linux-gnu.

Yours sleepy,

Paolo Carlini <pcarlini@unitus.it>

        libstdc++/4402
        * testsuite/27_io/ostream_inserter_arith.cc (test02): add testcase.
        * include/bits/locale_facets.tcc (num_put::_M_convert_float): deal
        properly with long ios_base::fixed floats.
        * include/bits/locale_facets.tcc (num_put::_M_widen_float): use __len in
        __builtin_alloca call, correct comment.
        * include/bits/locale_facets.tcc (num_put::_M_insert): fix conditional,
        use __w in __builtin_alloca call.


diff -urN gcc-vanilla/libstdc++-v3/include/bits/locale_facets.tcc
gcc/libstdc++-v3/include/bits/locale_facets.tcc
--- gcc-vanilla/libstdc++-v3/include/bits/locale_facets.tcc Thu Nov 29 23:59:37 2001
+++ gcc/libstdc++-v3/include/bits/locale_facets.tcc Sun Dec  2 01:07:04 2001
@@ -716,10 +716,18 @@
  // Protect against sprintf() buffer overflows.
  if (__prec > __max_prec)
    __prec = __max_prec;
-
  // Long enough for the max format spec.
  char __fbuf[16];
- char __cs[64];
+
+ // Consider the possibility of long ios_base::fixed outputs
+ const bool __long_fixed =
+   ((__io.flags() & ios_base::fixed) && (__v < -1e35 || __v > 1e35));
+ const int __cs_size = __long_fixed ?
+   numeric_limits<_ValueT>::max_exponent10 + __max_prec + 4
+   : __max_prec*4;
+ char* __cs =
+          static_cast<char*>(__builtin_alloca(sizeof(char) * __cs_size));
+
  int __len;
  // [22.2.2.2.2] Stage 1, numeric conversion to character.
  if (_S_format_float(__io, __fbuf, __mod, __prec))
@@ -754,12 +762,14 @@
      int __len) const
     {
       // [22.2.2.2.2] Stage 2, convert to char_type, using correct
-      // numpunct.decimal_point() values for '.' and adding grouping.
+      // numpunct.decimal_point() values for '.'.
       const locale __loc = __io.getloc();
       const ctype<_CharT>& __ctype = use_facet<ctype<_CharT> >(__loc);
-      _CharT* __ws = static_cast<_CharT*>(__builtin_alloca(sizeof(_CharT) * 64));
+
+      _CharT* __ws =
+         static_cast<_CharT*>(__builtin_alloca(sizeof(_CharT) * __len));
       __ctype.widen(__cs, __cs + __len, __ws);
-
+
       const numpunct<_CharT>& __np = use_facet<numpunct<_CharT> >(__loc);
       // Replace decimal point.
       const _CharT* __p;
@@ -810,10 +820,11 @@
        int __len) const
     {
       // [22.2.2.2.2] Stage 3.
-      _CharT* __ws2 = static_cast<_CharT*>(__builtin_alloca(sizeof(_CharT) * 64));
       streamsize __w = __io.width();
+      _CharT* __ws2;
       if (__w > static_cast<streamsize>(__len))
         {
+          __ws2 = static_cast<_CharT*>(__builtin_alloca(sizeof(_CharT) * __w));
           __pad(__io, __fill, __ws2, __ws, __w, __len, true);
           __len = static_cast<int>(__w);
           // Switch strings.
diff -urN gcc-vanilla/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc
gcc/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc
--- gcc-vanilla/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc Thu Nov 29 23:59:38
2001
+++ gcc/libstdc++-v3/testsuite/27_io/ostream_inserter_arith.cc Sat Dec  1 11:25:07 2001
@@ -272,6 +272,22 @@
 #endif
   VERIFY(os && os.str() == largebuf);

+  // make sure we can output a long float in fixed format
+  // without seg-faulting (libstdc++/4402)
+  double val2 = 3.5e230;
+
+  ostringstream os2;
+  os2.precision(3);
+  os2.setf(ios::fixed);
+  os2 << val2;
+
+  sprintf(largebuf, "%.*f", 3, val2);
+#ifdef TEST_NUMPUT_VERBOSE
+  cout << "expect: " << largebuf << endl;
+  cout << "result: " << os2.str() << endl;
+#endif
+  VERIFY(os2 && os2.str() == largebuf);
+
   return 0;
 }