Hi, > Unfortunately this breaks the build of today's linux-next for the Meta > architecture (arch/metag), which happens to use a fairly old compiler > (based on gcc 4.2.4) which I presume is the reason why. That's very odd. Unfortunately, I don't have most of arch/metag, it seems, where could I get it? In particular no gup.c exists for metag in Linus's current tree. > A bunch of compile time asserts fail, even in code which should be > optimised out. E.g. here's one which I analysed: > > mm/gup.c: In function ‘follow_page_mask’: > mm/gup.c:208: error: size of array ‘type name’ is negative > > Line 208 uses HPAGE_PMD_NR which expands to a HPAGE_PMD_SHIFT, which > expands to a BUILD_BUG(). However that line is inside an if block > conditioned on pmd_trans_huge(*pmd) which include/asm-generic/pgtable.h > defines inline to return 0, so the whole block should already be being > optimised out. > > I don't understand why your patch should break things, I suspect it's > related to the sparse behaviour you're trying to work around, but can we > please drop this patch until a more portable workaround can be found? > I'm happy to test further patches with metag if it helps. I don't really understand that either - if the compiler could prove that the assignment to __cond was a constant, and remember that __cond is now constant, I don't really see why it can't follow that through and consider "!(condition)" a const?? I suppose the other option for the original problem is to ignore _compiletime_assert() for sparse, like we do for BUG_ON(), but it'd probably be good to analyse more why this particular code is broken now. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
