Fix unused variable warning in GCC 16+

[ilazaric]

Locally I built this with trunk GCC and noticed warnings:

In file included from /home/ilazaric/repos/ALL/submodules/edg-compiler/src/fe_common.h:71,
                 from /home/ilazaric/repos/ALL/submodules/edg-compiler/src/c_gen_be.c:45:
/home/ilazaric/repos/ALL/submodules/edg-compiler/src/util.h: In instantiation of 'void edg::detail::append_with_custom_reserve(a_Reserve_fn, a_Text_convertible_type ...) [with a_Reserve_fn = edg::Allocated_string<edg::Delegate_buffered_allocator<50, edg::General_allocator>::Meta>::Allocated_string<>(const an_allocator&)::<lambda(size_t)>; a_Text_convertible_type = {}]':
/home/ilazaric/repos/ALL/submodules/edg-compiler/src/util.h:4957:37:   required from 'edg::Allocated_string<Allocator>::Allocated_string(const an_allocator&, a_Text_convertible_type ...) [with a_Text_convertible_type = {}; Allocator = edg::Delegate_buffered_allocator<50, edg::General_allocator>::Meta; an_allocator = edg::Delegate_buffered_allocator<50, edg::General_allocator>::Meta<char>]'
 4957 |   detail::append_with_custom_reserve(reserve_func, args...);
      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
/home/ilazaric/repos/ALL/submodules/edg-compiler/src/util.h:4905:47:   required from 'edg::Allocated_string<Allocator>::Allocated_string(a_Text_convertible_type ...) [with a_Text_convertible_type = {}; Allocator = edg::Delegate_buffered_allocator<50, edg::General_allocator>::Meta]'
 4905 |     : Allocated_string(an_allocator{}, args...)
      |                                               ^
/home/ilazaric/repos/ALL/submodules/edg-compiler/src/c_gen_be.c:4141:22:   required from here
 4141 |     Small_string<50> buffer;
      |                      ^~~~~~
/home/ilazaric/repos/ALL/submodules/edg-compiler/src/util.h:4861:10: warning: variable 'counter' set but not used [-Wunused-but-set-variable=]
 4861 |   size_t counter = 0;
      |          ^~~~~~~

Tried a couple of different GCC versions, and first one that warns is GCC 16.

Minimum warning to see this: -Wunused-but-set-variable=2 , which is implied by the build

It seems GCC warns now if a variable is only used in a pack expansion over an empty pack.
I believe this is equivalent to: https://godbolt.org/z/o4535qKqc

Don't think it has much interesting info, but just noting how I configured and built:

# GCC trunk installed to /opt/GCC-release, and bin is in PATH
export EDG_BASE="$PWD/bases/docker/dev-env/gcc"
time LDFLAGS='-Wl,-rpath=/opt/GCC-release/lib64' cmake --preset linux-gcc-release -DEDG_CPP_RT_LIBS=linux_x86_64
time LDFLAGS='-Wl,-rpath=/opt/GCC-release/lib64' cmake --build build/gcc-release/ --target src/cmake/cpfe/CMakeFiles/cpfe.dir/__/__/c_gen_be.c.o --clean-first --verbose

If needed, I can cook up a podman reproducer

Not very relevant, but interesting to me, the warning disappears if operator[] is not on class, but pointer:
https://godbolt.org/z/1G1aWcKan

After this fix, haven't seen any warning over full build

[daveedvdv-nvidia]

Looks good in principle. Just the formatting nit I pointed out.
I think this doesn't need a Changes entry.

[ilazaric]

@daveedvdv-nvidia I think your nit message got lost, I assume you meant I should align the variable identifiers? If so, I believe I updated it to look as rest of codebase.

[daveedvdv-nvidia]

I think your nit message got lost,

Ah, I probably forgot to click something...

I assume you meant I should align the variable identifiers?

Exactly. Your change looks good!

[daveedvdv-nvidia]

Merged as b8d3a78