Messages in this thread | | | Date | Fri, 30 May 2014 13:21:14 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH v2 2/2] x86,vdso: Fix cross-compilation from big-endian architectures |
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On 05/30/2014 01:09 PM, Andy Lutomirski wrote: >> >> I came up with the following, it seems like a reasonable simplification: >> >>> #define _LE(x, bits, ifnot) \ >>> __builtin_choose_expr( \ >>> (sizeof(x) == bits/8), \ >>> (__typeof__(x))le##bits##toh(x), ifnot) > > This will do awful things if x is a floating-point type, and, for > integers, the cast is probably unnecessary. But it should be okay. >
I mostly wanted to preserve the signedness. Yes, if we care about floating-point it gets trickier.
At some point hopefully there will be a native C feature to handle this crap.
>>> extern void bad_le(uint64_t); > > If this ever goes in a common header, then we should do the > __attribute__((error)) thing. I wonder if it would ever make sense to > have __LINUX_HOSTPROG__ and make some of the basic headers work. Hmm. > >>> #define _LAST_LE(x) \ >>> __builtin_choose_expr(sizeof(x) == 1, (x), bad_le(x)) >>> >>> #define LE(x) \ >>> _LE(x, 64, _LE(x, 32, _LE(x, 16, _LAST_LE(x)))) >> >> What do you think? > > My only real real objection is that _LE sounds like converting *to* > little-endian to me. Admittedly, that's the same thing on any > remotely sane architecture, but still.
GET_LE() then?
-hpa
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