Re: [PATCH] libgccjit: Support signed char flag

[David Malcolm <dmalcolm@redhat.com>]

On Thu, 2023-12-21 at 08:42 -0500, Antoni Boucher wrote:
> Hi.
> This patch adds support for the -fsigned-char flag.

Thanks.  The patch looks correct to me.

> I'm not sure how to test it since I stumbled upon this bug when I
> found
> this other bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107863)
> which is now fixed.
> Any idea how I could test this patch?

We already document that GCC_JIT_TYPE_CHAR has "some signedness".  The
bug being fixed here is that gcc_jit_context compilations were always
treating "char" as unsigned, regardless of the value of -fsigned-char
(either from the target's default, or as a context option), when it
makes more sense to follow the C frontend's behavior.

So perhaps jit-written code with a context that has -fsigned-char as an
option (via gcc_jit_context_add_command_line_option), and which
promotes a negative char to a signed int, and then returns the result
as an int?  Presumably if we're erroneously forcing "char" to be
unsigned, the int will be in the range 0x80 to 0xff, rather that being
negative.

Dave