Re: Libm core dump with SIGILL

[Anders Magnusson <ragge%ludd.ltu.se@localhost>]

Greg Stark skrev den 2015-08-21 14:35:
> While running the Postgres regression tests I found that the exp()
> function in libm gets a SIGILL with certain arguments.
>
> simh$  gcc -Wall  exp.c -lm
> simh$ ./a.out
> [4]   Illegal instruction (core dumped) ./a.out
>
> On a modern architecture with IEEE floats:
>
> $ gcc -Wall  exp.c -lm
> $ ./a.out
> exp(88.0297) = 1.70141e+38
>
> I know the VAX floating points are not exactly IEEE and they may not
> be able to represent this value but I would expect them to get a FPE
> or signal overflow in some other way, not get a SIGILL?
Well, not in VAX FP.  From the man page for exp:

RETURN VALUES
     These functions will return the appropriate computation unless an 
error
     occurs or an argument is out of range.  The functions exp() and 
expm1()
     detect if the computed value will overflow, set the global 
variable errno
     to ERANGE and cause a reserved operand fault on a VAX.

So, it is following the specs... :-)

-- Ragge