Re: long double (was "strtold?")

[Ken Werner <ken at linux dot vnet dot ibm dot com>]

On Monday 20 April 2009 23:15:24 Howland Craig D (Craig) wrote:
> Ken said:
> >I played with the AC_TYPE_LONG_DOUBLE_WIDER macro but there are two
> >things to consider. We would need to upgrade the autoconf version required 
> >by newlib and introduce something like config.h (through AC_CONFIG_HEADERS). 
> >which might pollute the name space if it get's pulled by a standard header.
>
> Jeff said:
> >I think an executable test is required to accomplish this which can't be
> >done in newlib due to the missing library at time of configure.
>
> Ken's former problem could easily be circumvented by writing our own
> test
> as he did for HAVE_LONG_DOUBLE, couldn't it?  Something like:
>
> cat >conftest.c <<EOF
> #include <float.h>
> #if DBL_MANT_DIG == LDBL_MANT_DIG  &&  LDBL_MIN_EXP == DBL_MIN_EXP  &&
> \
>     LDBL_MAX_EXP == DBL_MAX_EXP
>   #define _LDBL_EQ_DBL
>  #else
>   #error "LDBL != DBL"
> #endif
> EOF
>
> (Of course, the #define is meaningless, but I just copied what we have
> already and did a minimal amount of editing.  Maybe a declaration would
> be needed in case there were any compilers that didn't like to make
> empty objects.)
>
> This is not an executable test that needs the library, as float.h comes
> from the compiler.  It just takes a compile-only pass/fail.  So I think
> that it is viable, should we decide on this as the best alternative.
>
> I don't understand Ken's latter comment about name space pollution.
> Could
> you elaborate?

This is what I had in mind. Let's assume the generated config.h contains a 
define without an underscore prefix. If this gets pulled into a standard header 
we would have defines that are not standardized and thus not expected by the 
user. That might collide with user defined flags and cause side effects.
In case we write the conftest ourselfs and manually generate the header file to 
be included we can prepend the underscore. However, autoconf isn't my strong 
point. : )

> Craig

Ken