[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH 7/7] qobject atomics osdep: Make a few macros more hygienic



On 1/9/23 14:59, Cédric Le Goater wrote:
On 8/31/23 16:30, Eric Blake wrote:
On Thu, Aug 31, 2023 at 03:25:46PM +0200, Markus Armbruster wrote:

[This paragraph written last: Bear with my stream of consciousness
review below, where I end up duplicating some of the conslusions you
reached before the point where I saw where the patch was headed]

Variables declared in macros can shadow other variables.  Much of the
time, this is harmless, e.g.:

     #define _FDT(exp)                                                  \          do {                                                           \              int ret = (exp);                                           \              if (ret < 0) {                                             \
                 error_report("error creating device tree: %s: %s",   \
                         #exp, fdt_strerror(ret));                      \ exit(1);                                               \ }                                                          \
         } while (0)

Which is why I've seen some projects require a strict namespace
separation: if all macro parameters and any identifiers declared in
macros use either a leading or a trailing _ (I prefer a trailing one,
to avoid risking conflicts with libc reserved namespace; but leading
is usually okay), and all other identifiers avoid that namespace, then
you will never have shadowing by calling a macro from normal code.

I started fixing the _FDT() macro since it is quite noisy at compile.
Same for qemu_fdt_setprop_cells(). So are we ok with names like 'ret_'
and 'i_' ? I used a 'local_' prefix for now but I can change.

See https://lore.kernel.org/qemu-devel/20230831225607.30829-12-philmd@xxxxxxxxxx/




 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.