Re: [PATCH v3 02/15] cpus: Add const-qualified CPU environment accessors

[Richard Henderson <richard.henderson@linaro.org>]

On 8/21/26 08:51, Philippe Mathieu-Daudé wrote:
> No, this now fails distinctly on Ubuntu 24.04:
> 
> In file included from ../accel/tcg/tcg-runtime.c:26:
> ../accel/tcg/tcg-runtime.c: In function ‘helper_exit_atomic’:
> /home/runner/work/qemu/qemu/include/exec/cpu-common.h:100:31: error: expected expression 
> before ‘typeof’
>    100 | #define env_cpu(env) _Generic(typeof(*env), \
>        |                               ^~~~~~
> ../accel/tcg/tcg-runtime.c:135:26: note: in expansion of macro ‘env_cpu’
>    135 |     cpu_loop_exit_atomic(env_cpu(env), GETPC());
>        |                          ^~~~~~~

Yeah, this of course fails because _Generic wants an expression and typeof() is a type not 
an expression.

However, in this case less is more -- just don't dereference env:

#define env_cpu(env) _Generic(env, \
             CPUArchState *: \
                 (CPUState *)((void *)(env) - sizeof(CPUState)), \
             const CPUArchState *: \
                 (const CPUState *)((const void *)(env) - sizeof(CPUState)))

etc.  It's only top-level qualifiers that are stripped (so const int -> const), but 
qualified pointers aren't top level (so const int * and int * do not match).


r~