On Tue, 2022-09-06 at 15:20 -0700, Brian Norris wrote: > Hi, > > On Sun, Sep 04, 2022 at 09:29:07PM +0200, Johannes Berg wrote: > > From: Johannes Berg <johannes.berg@xxxxxxxxx> > > > > There are two, just change them to have a "u8 data[]" type > > member, and add casts where needed. No binary changes. > > Hmm, what exact warning are you looking at? This one? > https://clang.llvm.org/docs/DiagnosticsReference.html#wflexible-array-extensions > I think gcc also has one with W=1 now? But yes, it's similar to that one. I was looking at Jakub's netdev test builds here: https://patchwork.hopto.org/static/nipa/673828/12964988/build_32bit/stderr ../drivers/net/wireless/marvell/mwifiex/fw.h:2107:46: warning: array of flexible structures ../drivers/net/wireless/marvell/mwifiex/fw.h:2257:47: warning: array of flexible structures > > @@ -2104,7 +2104,7 @@ struct mwifiex_fw_mef_entry { > > struct host_cmd_ds_mef_cfg { > > __le32 criteria; > > __le16 num_entries; > > - struct mwifiex_fw_mef_entry mef_entry[]; > > + u8 mef_entry_data[]; > > Do you actually need this part of the change? The 'mef_entry' (or > 'mef_entry_data') field is not actually used anywhere now, but I can't > tell what kind of warning is involved. But it itself is variable, so the compiler is (rightfully, IMHO) saying that you can't have an array of something that has a variable size, even if it's a variable array. > > struct host_cmd_ds_coalesce_cfg { > > __le16 action; > > __le16 num_of_rules; > > - struct coalesce_receive_filt_rule rule[]; > > + u8 rule_data[]; > > These kinds of changes seem to be losing some valuable information. At a > minimum, it would be nice to leave a comment that points at the intended > struct; but ideally, we'd be able to still get the type safety from > actually using the struct, instead of relying on casts and/or u8/void. All fair points. This was the way we typically do this in e.g. ieee80211.h ("u8 variable[]", not "struct element elems[]"), but YMMV. I thought later after Kalle asked about making it a single entry such as struct coalesce_receive_filt_rule first_rule; but then the sizeof() is messed up and then the change has to be much more careful. Anyway, I was mostly trying to remove some warnings in drivers that don't really have a very active maintainer anymore, since we have so many in wireless it sometimes makes it hard to see which ones are new. No particular feelings about this patch :-) johannes
