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Re: AC_C_LONG_DOUBLE is obsolescent.

From: Eric Blake
Subject: Re: AC_C_LONG_DOUBLE is obsolescent.
Date: Wed, 09 Apr 2008 13:05:49 -0600
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According to Bob Friesenhahn on 4/9/2008 12:35 PM:
| I am confused since I don't see how the usefullness of this test can be
| obsolescent.

The test was merely whether compilers support the type 'long double'; as
all modern compilers obey this part of the C standard, it is no longer
worth checking whether long double is syntactically valid, and rather just
assuming that it is.

On the other hand, the properties of long double are still very much a
portability nightmare, and many libm lack long double support even though
the compiler supports a long double type.  Gnulib has some macros that do
much more extensive testing of long double's properies; you are better off
using those macros than trying to make AC_C_LONG_DOUBLE learn all of these
properties of the type.

| I am also confused by the use of the term "current systems" since
| perhaps it means some specific version of Linux/glibc rather than the
| set of still running systems on which an autoconf configure script may
| be executed.  If autoconf is targeted toward "current systems" then a
| definition of what this means (i.e. the criteria for which systems are
| no longer supported) should be documented.

Yes, current systems is intended to mean any system that an autoconf
configure script will run on.  It excludes platforms like Solaris 4, which
are no longer supported by the vendor.

At any rate, I am not opposed to re-adding AC_C_LONG_DOUBLE as a
non-obsolescent macro if gnulib's approach is inadequate and if using the
macro provides enough useful other properties that are still relevant in
modern porting targets.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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