Re: [PATCH] tcg/tci: fix logic error when registering helpers via FFI

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

On 10/28/22 18:21, Icenowy Zheng wrote:
> When registering helpers via FFI for TCI, the inner loop that iterates
> parameters of the helper reuses (and thus pollutes) the same variable
> used by the outer loop that iterates all helpers, thus made some helpers
> unregistered.
> 
> Fix this logic error by using a dedicated temporary variable for the
> inner loop.
> 
> Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> ---
>   tcg/tcg.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index 612a12f58f..adfaf61a32 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -619,6 +619,7 @@ static void tcg_context_init(unsigned max_cpus)
>           gpointer hash = (gpointer)(uintptr_t)typemask;
>           ffi_status status;
>           int nargs;
> +        int j;
>   
>           if (g_hash_table_lookup(ffi_table, hash)) {
>               continue;
> @@ -634,9 +635,9 @@ static void tcg_context_init(unsigned max_cpus)
>   
>           if (nargs != 0) {
>               ca->cif.arg_types = ca->args;
> -            for (i = 0; i < nargs; ++i) {
> -                int typecode = extract32(typemask, (i + 1) * 3, 3);
> -                ca->args[i] = typecode_to_ffi[typecode];
> +            for (j = 0; j < nargs; ++j) {
> +                int typecode = extract32(typemask, (j + 1) * 3, 3);
> +                ca->args[j] = typecode_to_ffi[typecode];

Oh my.  I'm surprised any test cases at all worked.
Queued to tcg-next, with the declaration of j moved to the loop itself:

	for (int j = 0; j < nargs; ++j)


r~