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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/dom0-build: fix build with clang5
On 15.07.2019 15:49, Andrew Cooper wrote: > On 15/07/2019 11:35, Jan Beulich wrote: >> With non-empty CONFIG_DOM0_MEM clang5 produces >> >> dom0_build.c:344:24: error: use of logical '&&' with constant operand >> [-Werror,-Wconstant-logical-operand] >> if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] ) >> ^ ~~~~~~~~~~~~~~~~~~ >> dom0_build.c:344:24: note: use '&' for a bitwise operation >> if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] ) >> ^~ >> & >> dom0_build.c:344:24: note: remove constant to silence this warning >> if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] ) >> ~^~~~~~~~~~~~~~~~~~~~~ >> 1 error generated. >> >> Obviously neither of the two suggestions are an option here. Oddly >> enough swapping the operands of the && helps, while e.g. casting or >> parenthesizing doesn't. Another workable variant looks to be the use of >> !! on the constant. >> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> >> --- >> I'm open to going the !! or yet some different route. No matter which >> one we choose, I'm afraid it is going to remain guesswork what newer >> (and future) versions of clang will choke on. >> >> --- a/xen/arch/x86/dom0_build.c >> +++ b/xen/arch/x86/dom0_build.c >> @@ -341,7 +341,7 @@ unsigned long __init dom0_compute_nr_pag >> unsigned long avail = 0, nr_pages, min_pages, max_pages; >> bool need_paging; >> >> - if ( !dom0_mem_set && CONFIG_DOM0_MEM[0] ) >> + if ( CONFIG_DOM0_MEM[0] && !dom0_mem_set ) >> parse_dom0_mem(CONFIG_DOM0_MEM); > > First and foremost, there is an identical construct on the ARM side, > which wants an equivalent adjustment. Oh, indeed. I should have remembered ... > As to the change, I'm going to suggest what I suggested instead of this > the first time around, which is strlen(CONFIG_DOM0_MEM) to make the > logic easier to follow. How does use of strlen() make anything easier? I think it is a pretty common pattern to check the first character for nul if all one is after is to know whether a string is empty. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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