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Re: AC_CHECK_SIZEOF for members

From: Sam Steingold
Subject: Re: AC_CHECK_SIZEOF for members
Date: Wed, 11 May 2005 09:49:27 -0400
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (windows-nt)

> * Paul Eggert <address@hidden> [2005-05-10 16:46:27 -0700]:
> Sam Steingold <address@hidden> writes:
>> it appears that AC_CHECK_SIZEOF works only with types, not members.
> Yes, that's correct.  You'd need to write a variant to do what you want.

<screaming in pain>

> Wouldn't it be easier to do this within C?  E.g.:
>    struct utmpx u;
>    enum {
>        (sizeof u.ut_tv != sizeof (struct timeval))
>    };
>    if (GLIBC_2_3_2_STRUCT_UTMPX_BUG) ...

yes, it is easy - but the same holds for sizeof(type_t) - and you _do_
provide a test for that.

the reason I want a CPP macro and not a run-time if is that the code
will end up looking like this:

  if (size_of(u.ut_tv.tv_sec) = 4)

the result is that on _each_ platform there will be a compile-time
warning about a wrong argument type.


Sam Steingold ( running w2k
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