[Bug libfortran/24685] real(16) formatted input is broken for huge values (gfortran.dg/default_format_2.f90)

[dominiq at lps dot ens dot fr]

------- Comment #28 from dominiq at lps dot ens dot fr  2008-01-24 14:01 -------
Some remarks from powerpc-apple-darwin9:

(1) the title is misleading: formatted inputs are not broken, formatted outputs
are.

(2) they seem broken for constants nearest from bellow any power of two, as
shown by the following code:

[karma] bug/real16% cat real_16_red.f90
real(16) :: x
x = 1.0_16
print *, nearest(x,-x), nearest(x,x)
print *, nearest(1.0_16,-1.0_16), nearest(1.0_16,1.0_16)
end
[karma] bug/real16% gfc -fno-range-check real_16_red.f90
[karma] bug/real16% a.out 
  0.99999999999999999999999999999998767        
1.0000000000000000000000000000000247      
  1.00000000000000000000000000000000000       
1.00000000000000000000000000000002465      

where  nearest(1.0_16,-1.0_16) is ouput as 1.0...0 and not as 0.9...98767.

(3) As huge(1.0_16) is treated as a constant, I had to pay hide-and-seek with
gfortran in the following code:

[karma] bug/real16% cat huge_16.f90
character(80) :: tmp
real(16) :: x, y
x = 2.0_16**1022
print *, 2.0_16*x, 2.0_16*x-huge(x) ! 2.0_16**1023 is larger than huge(x) but
not printed as +Inf
y = nearest(4.0_16*x,-x)
print *, 4.0_16*x, nearest(2.0_16*x,x), nearest(y,-x)

x = nearest(2.0_16*x,-x)   ! hide huge in a variable
print *, x, x-huge(x)

write(tmp,*) x
read(tmp,*) y
print *, x, y, x-y        ! the printed value of y is not the same the one for
x

x = nearest(x,1.0_16)
print *, x, nearest(x,1.0_16)

print *, 8.98846567431157953864652595394512367E+0307_16
end
[karma] bug/real16% gfc -fno-range-check huge_16.f90
[karma] bug/real16% a.out
  8.98846567431157953864652595394512367E+0307 
1.10791393256022264271830208461724263E+0276
                                    +Infinity 
8.98846567431157953864652595394534525E+0307                                   
+Infinity
  8.98846567431157953864652595394501288E+0307  
0.0000000000000000000000000000000000      
  8.98846567431157953864652595394501288E+0307 
8.98846567431157953864652595394512367E+0307  
0.0000000000000000000000000000000000      
  8.98846567431157953864652595394512367E+0307 
8.98846567431157953864652595394534525E+0307
                                    +Infinity

where x is an hidden huge(x), correctly printed as
8.98846567431157953864652595394501288E+0307, correctly read as y (x-y==0.0),
while y is printed as 8.98846567431157953864652595394534525E+0307==+Inf.

Note also several value above huge(x) not printed as +Inf.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24685