Re: [U-Boot] [PATCH 3/3 v2] Replace CONFIG_SYS_GBL_DATA_SIZE by auto-generated value

Dear Alessandro Rubini,

In message 20101026211821.GA2528@morgana.i.gnudd.com you wrote:

...

Is it guaranteed (I mean by the C standard) that the alignment of a struct (which affects only the possible start address) also has effect on the sizeof() for that struct, in the sense that sizeof() is guaranteed to be a multiple of that alignment requirement?

Yes. Because if you make an array, all of them must be aligned, and the size of an array is a multiple of sizeof(array_item). While alignment is not in the standard, the sizeof/array relationship is.

I am not convinced, as we don't have an array context here.

It's in C99 draft (http://busybox.net/~landley/c99-draft.html)

  6.5.3.4 The sizeof operator

  #6

  EXAMPLE 2 Another use of the sizeof operator is to compute the
  number of elements in an array:
    sizeof array / sizeof array[0]

I don't see that with

struct foo x; struct foo y[N];

we have a guarantee that sizeof(x) == sizeof(y[0]).

Maybe I'm just paranoid...

Best regards,

Wolfgang Denk