From: Linus Torvalds Date: Sun, 20 Apr 2025 18:30:11 +0000 (-0700) Subject: gcc-15: work around sequence-point warning X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=ac71fabf15679fc7bc56c51bc92bd4b626564c37;p=nvme.git gcc-15: work around sequence-point warning The C sequence points are complicated things, and gcc-15 has apparently added a warning for the case where an object is both used and modified multiple times within the same sequence point. That's a great warning. Or rather, it would be a great warning, except gcc-15 seems to not really be very exact about it, and doesn't notice that the modification are to two entirely different members of the same object: the array counter and the array entries. So that seems kind of silly. That said, the code that gcc complains about is unnecessarily complicated, so moving the array counter update into a separate statement seems like the most straightforward fix for these warnings: drivers/net/wireless/intel/iwlwifi/mld/d3.c: In function ‘iwl_mld_set_netdetect_info’: drivers/net/wireless/intel/iwlwifi/mld/d3.c:1102:66: error: operation on ‘netdetect_info->n_matches’ may be undefined [-Werror=sequence-point] 1102 | netdetect_info->matches[netdetect_info->n_matches++] = match; | ~~~~~~~~~~~~~~~~~~~~~~~~~^~ drivers/net/wireless/intel/iwlwifi/mld/d3.c:1120:58: error: operation on ‘match->n_channels’ may be undefined [-Werror=sequence-point] 1120 | match->channels[match->n_channels++] = | ~~~~~~~~~~~~~~~~~^~ side note: the code at that second warning is actively buggy, and only works on little-endian machines that don't do strict alignment checks. The code casts an array of integers into an array of unsigned long in order to use our bitmap iterators. That happens to work fine on any sane architecture, but it's still wrong. This does *not* fix that more serious problem. This only splits the two assignments into two statements and fixes the compiler warning. I need to get rid of the new warnings in order to be able to actually do any build testing. Signed-off-by: Linus Torvalds --- diff --git a/drivers/net/wireless/intel/iwlwifi/mld/d3.c b/drivers/net/wireless/intel/iwlwifi/mld/d3.c index 2c6e8ecd93b7..ee99298eebf5 100644 --- a/drivers/net/wireless/intel/iwlwifi/mld/d3.c +++ b/drivers/net/wireless/intel/iwlwifi/mld/d3.c @@ -1099,7 +1099,8 @@ iwl_mld_set_netdetect_info(struct iwl_mld *mld, if (!match) return; - netdetect_info->matches[netdetect_info->n_matches++] = match; + netdetect_info->matches[netdetect_info->n_matches] = match; + netdetect_info->n_matches++; /* We inverted the order of the SSIDs in the scan * request, so invert the index here. @@ -1116,9 +1117,11 @@ iwl_mld_set_netdetect_info(struct iwl_mld *mld, for_each_set_bit(j, (unsigned long *)&matches[i].matching_channels[0], - sizeof(matches[i].matching_channels)) - match->channels[match->n_channels++] = + sizeof(matches[i].matching_channels)) { + match->channels[match->n_channels] = netdetect_cfg->channels[j]->center_freq; + match->n_channels++; + } } }