r323008 - [Lex] Fix crash on code completion in comment in included file.

[Hans Wennborg via cfe-commits]

Merged to 6.0 in r323333 as requested in PR36043. Richard, please
complain if you don't agree.

On Sat, Jan 20, 2018 at 12:41 AM, Volodymyr Sapsai via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: vsapsai
> Date: Fri Jan 19 15:41:47 2018
> New Revision: 323008
>
> URL: http://llvm.org/viewvc/llvm-project?rev=323008&view=rev
> Log:
> [Lex] Fix crash on code completion in comment in included file.
>
> This fixes PR32732 by updating CurLexerKind to reflect available lexers.
> We were hitting null pointer in Preprocessor::Lex because CurLexerKind
> was CLK_Lexer but CurLexer was null. And we set it to null in
> Preprocessor::HandleEndOfFile when exiting a file with code completion
> point.
>
> To reproduce the crash it is important for a comment to be inside a
> class specifier. In this case in Parser::ParseClassSpecifier we improve
> error recovery by pushing a semicolon token back into the preprocessor
> and later on try to lex a token because we haven't reached the end of
> file.
>
> Also clang crashes only on code completion in included file, i.e. when
> IncludeMacroStack is not empty. Though we reset CurLexer even if include
> stack is empty. The difference is that during pushing back a semicolon
> token, preprocessor calls EnterCachingLexMode which decides it is
> already in caching mode because various lexers are null and
> IncludeMacroStack is not empty. As the result, CurLexerKind remains
> CLK_Lexer instead of updating to CLK_CachingLexer.
>
> rdar://problem/34787685
>
> Reviewers: akyrtzi, doug.gregor, arphaman
>
> Reviewed By: arphaman
>
> Subscribers: cfe-commits, kfunk, arphaman, nemanjai, kbarton
>
> Differential Revision: https://reviews.llvm.org/D41688
>
> Added:
>     cfe/trunk/test/CodeCompletion/Inputs/comments.h
>     cfe/trunk/test/CodeCompletion/comments.cpp
> Modified:
>     cfe/trunk/lib/Lex/PPCaching.cpp
>     cfe/trunk/lib/Lex/PPLexerChange.cpp
>
> Modified: cfe/trunk/lib/Lex/PPCaching.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/PPCaching.cpp?rev=323008&r1=323007&r2=323008&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Lex/PPCaching.cpp (original)
> +++ cfe/trunk/lib/Lex/PPCaching.cpp Fri Jan 19 15:41:47 2018
> @@ -105,8 +105,10 @@ void Preprocessor::CachingLex(Token &Res
>  }
>
>  void Preprocessor::EnterCachingLexMode() {
> -  if (InCachingLexMode())
> +  if (InCachingLexMode()) {
> +    assert(CurLexerKind == CLK_CachingLexer && "Unexpected lexer kind");
>      return;
> +  }
>
>    PushIncludeMacroStack();
>    CurLexerKind = CLK_CachingLexer;
>
> Modified: cfe/trunk/lib/Lex/PPLexerChange.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/PPLexerChange.cpp?rev=323008&r1=323007&r2=323008&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Lex/PPLexerChange.cpp (original)
> +++ cfe/trunk/lib/Lex/PPLexerChange.cpp Fri Jan 19 15:41:47 2018
> @@ -444,6 +444,7 @@ bool Preprocessor::HandleEndOfFile(Token
>        }
>
>        CurPPLexer = nullptr;
> +      recomputeCurLexerKind();
>        return true;
>      }
>
>
> Added: cfe/trunk/test/CodeCompletion/Inputs/comments.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeCompletion/Inputs/comments.h?rev=323008&view=auto
> ==============================================================================
> --- cfe/trunk/test/CodeCompletion/Inputs/comments.h (added)
> +++ cfe/trunk/test/CodeCompletion/Inputs/comments.h Fri Jan 19 15:41:47 2018
> @@ -0,0 +1,4 @@
> +// PR32732
> +struct B {
> +  // <- code completion
> +};
>
> Added: cfe/trunk/test/CodeCompletion/comments.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeCompletion/comments.cpp?rev=323008&view=auto
> ==============================================================================
> --- cfe/trunk/test/CodeCompletion/comments.cpp (added)
> +++ cfe/trunk/test/CodeCompletion/comments.cpp Fri Jan 19 15:41:47 2018
> @@ -0,0 +1,13 @@
> +// Note: the run lines follow their respective tests, since line/column
> +// matter in this test.
> +
> +#include "comments.h"
> +
> +struct A {
> +  // <- code completion
> +  /* <- code completion */
> +};
> +
> +// RUN: %clang_cc1 -I %S/Inputs -fsyntax-only -code-completion-at=%s:7:6 %s
> +// RUN: %clang_cc1 -I %S/Inputs -fsyntax-only -code-completion-at=%s:8:6 %s
> +// RUN: %clang_cc1 -I %S/Inputs -fsyntax-only -code-completion-at=%S/Inputs/comments.h:3:6 %s
>
>
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