vsapsai added inline comments.
================ Comment at: clang/lib/Lex/Lexer.cpp:2012-2015 + // Skip escaped characters. Escaped newlines will already be processed by + // getAndAdvanceChar. + if (C == '\\') + C = getAndAdvanceChar(CurPtr, Result); ---------------- rsmith wrote: > vsapsai wrote: > > rsmith wrote: > > > You can just delete these four lines entirely. > > It will make Clang reject previously accepted `#include <test\>escape.h>` > > That's what we want, right? I agree with having no support for such file > > names, just want to confirm. For the reference, proposed change would match > > gcc 5.4.0 behaviour. gcc 6.1 and higher rejects such include too but in a > > different way. > Hmm. I thought so, but on further inspection this area is more subtle than > I'd anticipated. > > It's *permissible* to reject that. In C++, [lex.header]p2 says: "The > appearance of [...] the character[...] `\` [...] in a //q-char-sequence// or > an //h-char-sequence// is conditionally-supported with implementation-defined > semantics". C11 6.4.7/3 has similar wording but makes the behavior undefined > in that case. (Both GCC's behavior and Clang's behavior are permitted by > these rules.) > > Clang's handling of the `#include "q-char-sequence"` form behaves the same as > its handling of the `#include <h-char-sequence>` form today: the header name > is *not* terminated by a `"` or `>` (respectively) that is preceded by an odd > number of `\`s. Retaining this consistency of behavior seems like a good idea. > > However, the actual behavior when such a character is "escaped" does not seem > reasonable: > > ``` > #include <\>> // includes file named \>, not file named > > #include "\"" // includes file named \", not file named " > ``` > > ... and there is no general way to perform a double-quoted include of a file > whose name contains a `"` (not preceded by `\`), or an angled include of a > file whose name is `>` (not preceded by `>`). So it seems that permitting > escaped ending characters without actually handling them as escape sequences > is not particularly worthwhile. > > I think the best approach here is to follow GCC's lead: terminate a > //header-name// (of either form) when the first `"` or `>` character is > reached (depending on the form of header name), regardless of preceding `\`s. > > But... that's a more invasive change (you'll need to change the handling of > double-quoted string literals too, for consistency). Let's keep that change > and this one separate. Thanks for in-depth explanation, that is useful. https://reviews.llvm.org/D41423 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
