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Stefano Stabellini ; Bertrand >> Marquis ; Volodymyr Babchuk >> ; Andrew Cooper ; >> Roger Pau Monné ; Wei Liu ; Jiamei Xie >> ; xen-devel@lists.xenproject.org; Julien Grall >> >> Subject: Re: [PATCH v6 1/8] xen: reuse x86 EFI stub functions for Arm >> >>>>>>> this way. >>>>> >>>>> I have taken a look into this warning: >>>>> This is because the "-fshort-wchar" flag causes GCC to generate >>>>> code that is not binary compatible with code generated without >>>>> that flag. Why this warning hasn't been triggered in Arm64 is >>>>> because we don't use any wchar in Arm64 codes. >>>> >>>> I don't think that's quite right - you actually say below that we >>>> do use it there when interacting with UEFI. There's no warning >>>> there solely because the information isn't embedded in the object >>>> files there, from all I can tell. >>>> >>> >>> Maybe I should describe it this way: Arm64 does not use wchar type >>> directly in any code for parameters, variables and return values. >>> So Arm64 object files are exactly the same with "-fshort-wchar" and >>> without "-fshort-wchar". >>> >>> Although Xen's EFI code interacts with UEFI firmware, similar to RPC >>> function calls, these code also do not explicitly use wchar. >> >> How does it not? There are ample string literals as well as enough >> uses of CHAR16 (the UEFI "abstraction" of wchar_t). >> > > But I don't think CHAR16 will be affected by -fshort-wchar, because we > have specified CHAR16 as unsigned short type in typedef. Oh, I didn't recall that anomaly. Yes, then only string literals are affected. Albeit I'd hope gnu-efi would at some point switch to using wchar_t as the underlying type, as long as the compiler provides it. Jan