<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div></div><div><br><div><div>On May 28, 2014, at 11:59 AM, Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">On Wed, May 28, 2014 at 2:45 PM, Reid Kleckner <<a href="mailto:rnk@google.com">rnk@google.com</a>> wrote:<br><blockquote type="cite">On Wed, May 28, 2014 at 6:42 AM, Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>wrote:<br><blockquote type="cite"><br>On Tue, May 27, 2014 at 6:28 PM, Reid Kleckner <<a href="mailto:rnk@google.com">rnk@google.com</a>> wrote:<br><blockquote type="cite">On Sat, May 24, 2014 at 8:28 AM, Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>wrote:<br><blockquote type="cite"><br><blockquote type="cite">My first idea is to add a tablegen property like "HasPrettyPrinter =<br>0<br>or 1"<br>that supresses emission of the default printPretty method. Then<br>again,<br>we<br>kind of want the default version when the GNU and C++11 spellings of<br>the<br>attribute are used.<br></blockquote><br>That seems like the wrong way to go about it though, since this is a<br>new *spelling*, not a wholly new semantic kind of attribute (which I<br>think we really want to avoid). We could possibly attach a custom<br>pretty printer to the spelling itself (a la a code block), but that<br>seems a bit skeezy because the arguments are rather important and the<br>spelling shouldn't have to care about the arguments.<br></blockquote><br><br>How about this: when generating the prettyPrint implementation, if there<br>is<br>a pragma spelling, call MyAttr::printPrettyPragma(...). Any attribute<br>with<br>a pragma spelling will have to provide this method in<br>lib/AST/AttrImpl.cpp.<br></blockquote><br>So my ultimate goal is for pragma attributes to mirror all of the<br>other attributes, where we can infer syntax and semantics just from<br>what's in Attr.td. But it's becoming more obvious to me that the<br>amount of work required to get there is rather large (mostly due to<br>the fact that pragma argument syntax is ALL over the place).<br><br>As a stopgap solution, it seems reasonable to me to rely on an<br>AdditionalMember being defined for pragmas (which is basically what<br>you're suggesting).<br><br>So if an attribute has a pragma spelling, it is required to have:<br><br>let AdditionalMembers = [{<br> void printPrettyPragma(raw_ostream &OS, const PrintingPolicy &Policy)<br>const {<br> }<br>}];<br></blockquote><br><br>Sure, but... I like writing C++ in .cpp files, not .td files. +1 for<br>defining it out of line in AttrImpl.cpp. :)<br></blockquote><br>That's an understandable desire, but a step in the wrong direction for<br>two reasons. 1) Anything declarative that we can put into the .td file<br>belongs in the .td file. There's nothing about this problem which<br>isn't declarative aside from the fact that we don't have the time<br>(yet) to make the proper declarations regarding parameter syntax. 2)<br>Putting it into AttrImpl.cpp decouples the logic from what gets<br>generated, which is far worse than writing some C++ code in a .td<br>file. You would have to write an out-of-line definition for<br>FooAttr::printPrettyPragma where the declaration gets automatically<br>generated for you elsewhere, which is rather ugly as sin when we<br>already have an alternative that suffices.<br><br>Also, this isn't a whole lot of complex C++ code either. The less of<br>it you write in the .td file, the more likely it is we will get the<br>declarative portions down without a mess of refactoring.<br><br>~Aaron</div></blockquote></div><br></div></body></html>