Re: [Tinycc-devel] Ready for Release 0.9.27

[grischka]

Vincent Lefevre wrote:
> Note that according to C99, a bit-field is a type ("unsigned int" here
> is just a type specifier). Just like an array is not the same type of
> the type of its elements. See 6.7.2.1p9 in C99:
>
>   A bit-field is interpreted as a signed or unsigned integer type
>   consisting of the specified number of bits.107) [...]
>
>   107) As specified in 6.7.2 above, if the actual type specifier
>        used is int or a typedef-name defined as int, then it is
>        implementation-defined whether the bit-field is signed or
>        unsigned.
>
> When interpreting the standard, it is important to consider the
> *whole* standard, not just individual sentences, which may be
> ambiguous.

If that were true then all your citations wouldn't prove anything ;)

> FYI, GCC 6 behaves in the same way with -std=c89, -std=c99 and -std=c11.
> Ditto for Clang 3.9.

I wouldn't really mind if we change the behavior.

Basically tccgen.c contains 8 lines (in gen_op/expr_cond) similar to

     if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (VT_LLONG | VT_UNSIGNED) ...
     if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (VT_INT | VT_UNSIGNED) ...

Maybe we just need to change these like this
     if ((t1 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == ....

Note that VT_BITFIELD set implies bit-field width < original type width.

--- grischka