[Bug ada/60977] New: Float_IO.Put fails on large floats when 'digits exceeds 15

[georggcc at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60977

            Bug ID: 60977
           Summary: Float_IO.Put fails on large floats when 'digits
                    exceeds 15
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: georggcc at googlemail dot com

with Ada.Text_IO;  use Ada.Text_IO;
with System;

procedure Float_Segfault is

   type Flt is digits System.Max_Digits;

   package Fio is new Float_IO (Flt);

begin
   Fio.Put (Item => Flt'Last,
            Aft => 1,
            Exp => 0);
end Float_Segfault;

Assumption:
Put should always print a large floating point number, or raise an exception.

The effects seen, however, on both Mac and on GNU/Linux include neither
a number output nor an exception such as Layout_Error. Rather, the
program hangs, or does other curious things.

Playing with some parameters, for example changing the Flt type,
  type Flt is digits System.Max_Digits - 2;
or dividing the parameter passed for Item by powers of 10 changes little. 

Seemingly this happens in System.Img_Real.Set_Real_Image, according to GDB.

On Mac:
$ uname -r -s -m
Darwin 11.4.2 x86_64
$ gnatmake -gnatVa -gnateF -gnatwa -gnatv float_segfault.adb 
gcc -c -gnatVa -gnateF -gnatwa -gnatv float_segfault.adb

GNAT 4.10.0 20140427 (experimental) [trunk revision 209835]
Copyright 1992-2014, Free Software Foundation, Inc.

Compiling: float_segfault.adb (source file time stamp: 2014-04-27 11:38:41)
 14 lines: No errors
gnatbind -x float_segfault.ali
gnatlink float_segfault.ali
$ ./float_segfault 
^C

(In this example screen, the program hangs.)

On GNU/Linux:

$ uname -r -o -m
2.6.32-5-amd64 x86_64 GNU/Linux
$ ./float_segfault 
Segmentation fault

Compilers used:

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/Users/bauhaus/mine/libexec/gcc/x86_64-apple-darwin11.4.2/4.10.0/lto-wrapper
Target: x86_64-apple-darwin11.4.2
Configured with: /Users/bauhaus/src/gcc/configure --prefix=/Users/bauhaus/mine
--disable-nls --disable-multilib --disable-libstdcxx-pch CC=gcc
--enable-languages=c,ada,c++,go --no-create --no-recursion
Thread model: posix
gcc version 4.10.0 20140427 (experimental) [trunk revision 209835] (GCC) 

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/home/bauhaus/opt/GNAT2013/bin/../libexec/gcc/x86_64-pc-linux-gnu/4.7.4/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../src/configure --enable-_cxa_atexit --enable-threads=posix
--enable-checking=release --enable-languages=ada,c,c++
--with-bugurl=URL:mailto:report@adacore.com --disable-nls
--without-libiconv-prefix --disable-libmudflap --disable-libstdcxx-pch
--disable-libada --disable-multilib
--with-mpfr=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/mpfr/install
--with-gmp=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/gmp/install
--with-mpc=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/mpc/install
--with-libelf=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/libelf/install
--with-build-time-tools=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/gcc/build/buildtools/bin
--prefix=/usr/gnat --build=x86_64-pc-linux-gnu : (reconfigured)
../src/configure --enable-_cxa_atexit --enable-threads=posix
--enable-checking=release --enable-languages=ada,c,c++
--with-bugurl=URL:mailto:report@adacore.com --disable-nls
--without-libiconv-prefix --disable-libmudflap --disable-libstdcxx-pch
--disable-libada --disable-multilib
--with-mpfr=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/mpfr/install
--with-gmp=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/gmp/install
--with-mpc=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/mpc/install
--with-libelf=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/libelf/install
--with-build-time-tools=/draa.a/gnatmail/sandbox/gpl-2013/x86_64-linux/gcc/build/buildtools/bin
--prefix=/usr/gnat --build=x86_64-pc-linux-gnu
Thread model: posix
gcc version 4.7.4 20130416 for GNAT GPL 2013 (20130314) (GCC)