[LLVMbugs] [Bug 13868] New: Nondeterministic order of diagnostics

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13868

             Bug #: 13868
           Summary: Nondeterministic order of diagnostics
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: zaffanella at cs.unipr.it
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 9228
  --> http://llvm.org/bugs/attachment.cgi?id=9228
Test program showing diagnostic ordering issue.

Using a (debug+assert) build of clang r164159, we are observing
nondeterministic ordering of the diagnostics produced for the attached file
nondet-diag.cc.

(Side note: issue was initially observed as a nondeterministic order in the
invocation of callback ASTConsumer::HandleCXXImplicitFunctionInstantiation.)


First output obtained lists first method m1 and then m2:
========================================================
$ Debug+Asserts/bin/clang++ -fsyntax-only nondet-diag.cc
nondet-diag.cc:20:8: error: virtual function 'B<int>::m1' has more than one
      final overrider in 'E<int>'
struct E : D1<T>, D2<T> {
       ^
nondet-diag.cc:24:10: note: in instantiation of template class 'E<int>'
      requested here
  E<int> e;
         ^
nondet-diag.cc:3:16: note: overridden virtual function is here
  virtual void m1();
               ^
nondet-diag.cc:9:8: note: final overrider of 'B<int>::m1' in 'D1<int>'
  void m1();
       ^
nondet-diag.cc:15:8: note: final overrider of 'B<int>::m1' in 'D2<int>'
  void m1();
       ^
nondet-diag.cc:20:8: error: virtual function 'B<int>::m2' has more than one
      final overrider in 'E<int>'
struct E : D1<T>, D2<T> {
       ^
nondet-diag.cc:4:16: note: overridden virtual function is here
  virtual void m2();
               ^
nondet-diag.cc:10:8: note: final overrider of 'B<int>::m2' in 'D1<int>'
  void m2();
       ^
nondet-diag.cc:16:8: note: final overrider of 'B<int>::m2' in 'D2<int>'
  void m2();
       ^
2 errors generated.
========================================================


On another run, output lists first method m2 and then m1:
========================================================
$ Debug+Asserts/bin/clang++ -fsyntax-only nondet-diag.cc
nondet-diag.cc:20:8: error: virtual function 'B<int>::m2' has more than one
      final overrider in 'E<int>'
struct E : D1<T>, D2<T> {
       ^
nondet-diag.cc:24:10: note: in instantiation of template class 'E<int>'
      requested here
  E<int> e;
         ^
nondet-diag.cc:4:16: note: overridden virtual function is here
  virtual void m2();
               ^
nondet-diag.cc:10:8: note: final overrider of 'B<int>::m2' in 'D1<int>'
  void m2();
       ^
nondet-diag.cc:16:8: note: final overrider of 'B<int>::m2' in 'D2<int>'
  void m2();
       ^
nondet-diag.cc:20:8: error: virtual function 'B<int>::m1' has more than one
      final overrider in 'E<int>'
struct E : D1<T>, D2<T> {
       ^
nondet-diag.cc:3:16: note: overridden virtual function is here
  virtual void m1();
               ^
nondet-diag.cc:9:8: note: final overrider of 'B<int>::m1' in 'D1<int>'
  void m1();
       ^
nondet-diag.cc:15:8: note: final overrider of 'B<int>::m1' in 'D2<int>'
  void m1();
       ^
2 errors generated.
========================================================

Usually, some 3 or 4 runs are enough.

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