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Re: AC_CHECK_SIZEOF


From: Ralf Wildenhues
Subject: Re: AC_CHECK_SIZEOF
Date: Thu, 12 Apr 2007 21:39:44 +0200
User-agent: Mutt/1.5.13 (2006-08-11)

* Paul Eggert wrote on Thu, Apr 12, 2007 at 02:12:21AM CEST:
> 
> I can, for C (except for AC_CHECK_ALIGNOF).  I can't see how to do it
> for C++, but perhaps a C++ wizard can figure that out later.  I
> installed this:
> 
> 2007-04-11  Paul Eggert  <address@hidden>
> 
>       * doc/autoconf.texi (Generic Types): Document the restrictions
>       on types imposed by AC_CHECK_TYPE, AC_CHECK_TYPES.
>       (Generic Compiler Characteristics): AC_CHECK_SIZEOF now works
>       with objects too.  Document the restrictions on its use.
>       Document the restrictions on AC_CHECK_ALIGNOF's type argument.
>       * lib/autoconf/types.m4 (_AC_CHECK_TYPE_NEW):
>       For C, just try sizeof (TYPE) and sizeof ((TYPE)); if the former
>       works but the latter doesn't, then it's a valid type.
>       This lets people use function types and so forth.
>       For C++ there doesn't seem to be a simple solution, so leave it alone.
>       (AC_CHECK_SIZEOF): Allow argument to be a variable.
>       (AC_CHECK_SIZEOF, AC_CHECK_ALIGNOF): Don't bother to invoke
>       AC_CHECK_TYPE; that wasn't documented or necessary.

This regresses wrt. AC_CHECK_SIZEOF(struct { ... }) for C++.
maintainer-check exposes this failure.

Would you prefer the testsuite to be adjusted (skip the `AC_CHECK_SIZEOF
struct' tests if CC is a C++ compiler) and thus match your doc change,
or rather have AC_CHECK_SIZEOF be specifically different for C++ like
AC_CHECK_TYPE is now?  At least in the former case I think NEWS should
mention this functionality regression.

Also, allowing objects for AC_CHECK_TYPE* should have a test, no?

Cheers,
Ralf




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