<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Nov 13, 2014 at 1:40 PM, Duncan P. N. Exon Smith <span dir="ltr"><<a href="mailto:dexonsmith@apple.com" target="_blank">dexonsmith@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5"><br>
> On 2014-Nov-13, at 13:36, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
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> On Thu, Nov 13, 2014 at 1:33 PM, Duncan P. N. Exon Smith <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:<br>
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> > On 2014-Nov-13, at 13:31, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
> ><br>
> ><br>
> ><br>
> > On Thu, Nov 13, 2014 at 12:59 PM, Duncan P. N. Exon Smith <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:<br>
> ><br>
> > > On 2014-Nov-13, at 10:35, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
> > ><br>
> > ><br>
> > ><br>
> > > On Thu, Nov 13, 2014 at 4:39 AM, Duncan P. N. Exon Smith <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:<br>
> > ><br>
> > > > On 2014 Nov 12, at 16:55, Keno Fischer <<a href="mailto:kfischer@college.harvard.edu">kfischer@college.harvard.edu</a>> wrote:<br>
> > > ><br>
> > > > Hi dexonsmith,<br>
> > > ><br>
> > > > In some instances (such as in BitCodeWriter - see <a href="http://reviews.llvm.org/D6184" target="_blank">http://reviews.llvm.org/D6184</a>),<br>
> > > > it is useful to get an unsiged version of the data pointer instead. This adds an<br>
> > > > appropriate API to be used in BitCodeWriter in a follow up commit.<br>
> > > ><br>
> > > > <a href="http://reviews.llvm.org/D6241" target="_blank">http://reviews.llvm.org/D6241</a><br>
> > > ><br>
> > > > Files:<br>
> > > > include/llvm/ADT/StringRef.h<br>
> > > > include/llvm/IR/Metadata.h<br>
> > > > <D6241.16125.patch><br>
> > ><br>
> > > This LGTM. I have minor nitpicks below that you can take or leave.<br>
> > ><br>
> > > @David, does this API make sense to you given Keno's use case [1]?<br>
> > ><br>
> > > While it matches that use case quite well (needing iterator begin/end) there are many other cases where we play the same game - getting uint8_t rather than just unsigned char:<br>
> > ><br>
> > > lib/Support/DataExtractor.cpp: return getU<uint8_t>(offset_ptr, this, IsLittleEndian, Data.data());<br>
> > > lib/Support/MD5.cpp: const uint8_t *Ptr = Data.data();<br>
> > > lib/Support/MD5.cpp: ArrayRef<uint8_t> SVal((const uint8_t *)Str.data(), Str.size());<br>
> > > lib/IR/Constants.cpp: const uint8_t *Data = reinterpret_cast<const uint8_t *>(Str.data());<br>
> > > lib/ProfileData/CoverageMappingReader.cpp: Result = decodeULEB128(reinterpret_cast<const uint8_t *>(Data.data()), &N);<br>
> > > lib/ProfileData/CoverageMappingReader.cpp: decodeULEB128(reinterpret_cast<const uint8_t *>(Data.data()), &N);<br>
> > > lib/ProfileData/CoverageMappingReader.cpp: decodeULEB128(reinterpret_cast<const uint8_t *>(Data.data()), &N);<br>
> > > lib/ExecutionEngine/RuntimeDyld/RuntimeDyldChecker.cpp: reinterpret_cast<const uint8_t *>(SectionMem.data()),<br>
> > > lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp: uint8_t *ArgDataPtr = ArgData.data();<br>
> > > lib/DebugInfo/DWARFFormValue.cpp: Value.data = reinterpret_cast<const uint8_t *>(str.data());<br>
> > > include/llvm/Support/FileOutputBuffer.h: return (uint8_t*)Region->data();<br>
> > > include/llvm/Support/FileOutputBuffer.h: return (uint8_t*)Region->data() + Region->size();<br>
> > > include/llvm/Object/ELF.h: return reinterpret_cast<const uint8_t *>(Buf.data());<br>
> > > include/llvm/MC/YAML.h: : Data(reinterpret_cast<const uint8_t *>(Data.data()), Data.size()),<br>
> > > tools/llvm-objdump/llvm-objdump.cpp: ArrayRef<uint8_t> Bytes(reinterpret_cast<const uint8_t *>(BytesStr.data()),<br>
> > > tools/llvm-objdump/MachODump.cpp: ArrayRef<uint8_t> Bytes(reinterpret_cast<const uint8_t *>(BytesStr.data()),<br>
> > > tools/llvm-mc/Disassembler.cpp: ArrayRef<uint8_t> Data(Bytes.first.data(), Bytes.first.size());<br>
> > > tools/llvm-readobj/StreamWriter.h: auto V = makeArrayRef(reinterpret_cast<const uint8_t*>(Value.data()),<br>
> > > tools/llvm-readobj/StreamWriter.h: auto V = makeArrayRef(reinterpret_cast<const uint8_t*>(Value.data()),<br>
> > > tools/llvm-readobj/StreamWriter.h: auto V = makeArrayRef(reinterpret_cast<const uint8_t*>(Value.data()),<br>
> > > tools/llvm-readobj/StreamWriter.h: auto V = makeArrayRef(reinterpret_cast<const uint8_t*>(Value.data()),<br>
> > ><br>
> > > In several of these cases we're interested in getting an ArrayRef<uint8_t> from the StringRef - so maybe that's a better primitive operation (it's annoying when interoperating with containers, I'll grant you - since you need to call it twice, or stash a local variable - but one day... we'll have range algorithms for this sort of thing - in the mean time we could have utility functions like those in this patch, but I think the primary operation should probably be "give me a raw (uint8_t) byte array for this StringRef")<br>
> > ><br>
> ><br>
> > Sure. Do you have a name in mind? `uref()`?<br>
> ><br>
> ><br>
> > If we're going with a C++-esque name: "ArrayRef<uint8_t> bytes()" ?<br>
> ><br>
><br>
> `bytes()` sounds like `char` to me. `ubytes()`?<br>
><br>
> Really? It seems like most places that want bytes deal with unsigned chars, and the existence of this method on a StringRef would imply that it's not just giving identical begin/end as the StringRef's own begin/end, I would imagine...<br>
><br>
> But if you particularly prefer ubytes, sure.<br>
><br>
> Then if someone needs a `signed char` they can add `sbytes()`.<br>
><br>
> sbytes is just a range over char which StringRef already is,<br>
<br>
</div></div>`char`, `unsigned char`, and `signed char` are three distinct types.<br>
If someone depends on have signed chars, they need to cast to<br>
`signed char`.<br>
<br>
It's implementation-defined whether `char` is signed, but it's a<br>
distinct type from the other two in either case.<br></blockquote><div><br></div><div>Thanks for the refresher/reminder - I was a bit vague/incorrect there.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<span class=""><br>
> I'm not sure we'd ever need this function (I think it'd be reasonable to have some conversion from StringRef to ArrayRef<char> if we ever need it - though I suspect we won't).<br>
<br>
</span>I would want to call the `ArrayRef<char>` version `bytes()`.<br></blockquote><div><br>And here.<br><br>s/char/signed char/ up there if it helps.<br><br>I'll try to resummarize: I don't think anyone ever really wants signed char in this context, either they don't care (and StringRef/ArrayRef<char> is sufficient - and /maybe/ one day we'll want to ensure an easy conversion between the two, but I don't think I've seen a use case yet & have some doubts about one actually coming into existence) or they want unsigned, which is why I think "bytes()" is fairly unambiguous - the only time you want anything other than the range of char is when you want a range of (unsigned) bytes.<br><br>But I'm not so adamantly against "ubytes" that I'd reject/block it if you prefer it.<br><br>- David<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="HOEnZb"><div class="h5"><br>
><br>
> ><br>
> > > Also see Aaron's recent -Wcast-qual fixing patches that touched several cases like this:<br>
> > > <a href="http://llvm.org/viewvc/llvm-project?view=revision&revision=221782" target="_blank">http://llvm.org/viewvc/llvm-project?view=revision&revision=221782</a><br>
> > > <a href="http://llvm.org/viewvc/llvm-project?view=revision&revision=221781" target="_blank">http://llvm.org/viewvc/llvm-project?view=revision&revision=221781</a><br>
> > ><br>
> > ><br>
> > > [1]: <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141103/243658.html" target="_blank">http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141103/243658.html</a><br>
> > ><br>
> > > > Index: include/llvm/ADT/StringRef.h<br>
> > > > ===================================================================<br>
> > > > --- include/llvm/ADT/StringRef.h<br>
> > > > +++ include/llvm/ADT/StringRef.h<br>
> > > > @@ -40,6 +40,7 @@<br>
> > > > class StringRef {<br>
> > > > public:<br>
> > > > typedef const char *iterator;<br>
> > > > + typedef unsigned const char *uiterator;<br>
> > ><br>
> > > This spelling is strange to me; I'd expect:<br>
> > ><br>
> > > typedef const unsigned char *uiterator;<br>
> > ><br>
> > > > typedef const char *const_iterator;<br>
> > > > static const size_t npos = ~size_t(0);<br>
> > > > typedef size_t size_type;<br>
> > > > @@ -88,8 +89,12 @@<br>
> > > > /// @{<br>
> > > ><br>
> > > > iterator begin() const { return Data; }<br>
> > > > + uiterator ubegin() const { return reinterpret_cast<uiterator>(Data); }<br>
> > ><br>
> > > I have a slight preference for:<br>
> > ><br>
> > > uiterator ubegin() const { return reinterpret_cast<uiterator>(begin()); }<br>
> > ><br>
> > > But mainly just to match my change to `uend()` below.<br>
> > ><br>
> > > ><br>
> > > > iterator end() const { return Data + Length; }<br>
> > > > + uiterator uend() const {<br>
> > > > + return reinterpret_cast<uiterator>(Data) + Length;<br>
> > > > + }<br>
> > ><br>
> > > I think this should be:<br>
> > ><br>
> > > uiterator uend() const { return reinterpret_cast<uiterator>(end()); }<br>
> > ><br>
> > > ><br>
> > > > /// @}<br>
> > > > /// @name String Operations<br>
> > > > Index: include/llvm/IR/Metadata.h<br>
> > > > ===================================================================<br>
> > > > --- include/llvm/IR/Metadata.h<br>
> > > > +++ include/llvm/IR/Metadata.h<br>
> > > > @@ -55,12 +55,15 @@<br>
> > > > unsigned getLength() const { return (unsigned)getName().size(); }<br>
> > > ><br>
> > > > typedef StringRef::iterator iterator;<br>
> > > > + typedef StringRef::uiterator uiterator;<br>
> > > ><br>
> > > > /// \brief Pointer to the first byte of the string.<br>
> > > > iterator begin() const { return getName().begin(); }<br>
> > > > + uiterator ubegin() const { return getName().ubegin(); }<br>
> > > ><br>
> > > > /// \brief Pointer to one byte past the end of the string.<br>
> > > > iterator end() const { return getName().end(); }<br>
> > > > + uiterator uend() const { return getName().uend(); }<br>
> > > ><br>
> > > > /// \brief Methods for support type inquiry through isa, cast, and dyn_cast.<br>
> > > > static bool classof(const Value *V) {<br>
> > > ><br>
> > ><br>
> > ><br>
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