Fix crash when current lexer is nullptr

[yvvan]

Summary

caused a crash in <memory> header reparse (msvc kit)

[bkramer]

Test case?

[yvvan]

Do you mean the testcase that runs only for windows with ms-extensions flag and msvc includes?
I don't know if clang has that kind of tests. Does it?

[yvvan]

And if you just meant how to reproduce:

You need to parse and reparse standard <memory> header (my current one is C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\memory). I can provide the options and a command line that I have if you can't reproduce it with default ones...

[bkramer]

Changes like this should come with a small, c-index-test based, test case so we don't reintroduce the same bug in the future.

[yvvan]

This comment was removed by yvvan.

[yvvan]

I have minimized the crash case and added simple test for it.

[ilya-biryukov]

I've also stumbled upon this crash. Here is an even simpler repro that crashes for me (does not involve includes):

#ifndef HEADER_GUARD

#define FOO(X) int fhjdfhsdjkfhjkshfjk;
FOO(base)

struct X {
  int a;
};

int test() {
  X v;
  v.
}
#endif

lib/Parse/Parser.cpp

519

This certainly fixes the crash, but aren't we breaking other things if we don't run replayConditionalStack?
I.e. won't we get spurious errors on #endif?

[ilya-biryukov]

lib/Parse/Parser.cpp

519

I get a spurious #endif without #if error with your fix. We need to figure out the right place to run replayPreambleConditionalStack.

@erikjv, any ideas?

[ilya-biryukov]

Here's an alternative fix that moves the replay... call into Preprocessor: https://reviews.llvm.org/D36872.
It also fixes the crash and doesn't add invalid compiler errors about non-matching #ifdefs.

lib/Parse/Parser.cpp

if(getLangOpts().Borland) {
     PP.SetPoisonReason(Ident___abnormal_termination,diag::err_seh___finally_block);
     PP.SetPoisonReason(Ident_AbnormalTermination,diag::err_seh___finally_block);
   }
 
   Actions.Initialize();
 
   // Prime the lexer look-ahead.
   ConsumeToken();
-
+  if (!PP.isCurrentLexer(nullptr))
     PP.replayPreambleConditionalStack();
 }
 
 void Parser::LateTemplateParserCleanupCallback(void *P) {
   // While this RAII helper doesn't bracket any actual work, the destructor will
   // clean up annotations that were created during ActOnEndOfTranslationUnit
   // when incremental processing is enabled.
   DestroyTemplateIdAnnotationsRAIIObj CleanupRAII(((Parser *)P)->TemplateIds);
 }

test/Index/std-begin-error.cpp

+#ifndef RC_INVOKED
+#include <xmemory>
+_STD_BEGIN
+}
+#endif /* RC_INVOKED */
+
+// RUN: env CINDEXTEST_EDITING=1 c-index-test -test-load-source-reparse 5 local -std=c++14 %S\std-begin-error.cpp 2> %t.err
+// RUN: not FileCheck < %t.err %s
+// CHECK: Failure: libclang crashed