Calling ProcessLine in an unnamed macro leave Cling in a broken state .. sometimes

[pcanal]

Description

In an unnamed macro having:

{
gROOT->ProcessLine(statement_1);
statement_2;
}

is process line by line (per se) and statement_2 should (and does in most case) be able to use declaration made in statement_1. In some circumstances it does not. One such circumstance is the test roottest-cling-return-constRetrunTest_WILL_FAIL which should actually succeed (the original problem is fixed by moving to Cling) but still fails (unexpectedly) with:

Processing run.C...
/Users/pcanal/root_working/code/master/roottest/cling/return/./run.C:7:1: error: unknown type name 't02'
t02 t;
^

Reproducer

With the files in trun.tar.gz
we can set that the declaration in the ProcessLine are properly seen in the next lines. For example this version of trun.C:

{
gROOT->ProcessLine(".L t1.C");
gROOT->ProcessLine(".L t2.C");
int i123 = t_1;
int j123 = t_2;
}

works fine. Note that issuing on the prompt right after the .x trun.C the command gROOT->SetDirLevel(t_1); or i123 = t_2; works as well.

But this version:

{
gROOT->ProcessLine(".L t1.C");
gROOT->ProcessLine(".L t2.C");
int i123 = t_1;
int j123 = t_2;
gROOT->SetDirLevel(t_1);
}

mysteriously fails with:

Processing trun.C...
/Users/pcanal/root_working/code/master/roottest/cling/return/./trun.C:7:1: error: cannot initialize an array element of type 'void *' with an rvalue of type 'TROOT *(*)()'
gROOT->SetDirLevel(t_1);
^~~~~
/Users/pcanal/root_working/builds/master-pr/include/TROOT.h:407:16: note: expanded from macro 'gROOT'
#define gROOT (ROOT::GetROOT())
               ^~~~~~~~~~~~~

The error seems to indicate that the parser is 'prefixing' to gROOT something related to array of void* and initialization

Similarly

{
gROOT->ProcessLine(".L t1.C");
gROOT->ProcessLine(".L t2.C");
int i123 = t_1;
int j123 = t_2;
i123 = t_2;
}

fails with:

Processing trun.C...
Assertion failed: (Node->getDependence() == ExprDependence::None), function VisitBinaryOperator, file DynamicLookup.cpp, line 628.
Abort trap: 6

And weirdly:

{
gROOT->ProcessLine(".L t1.C");
gROOT->ProcessLine(".L t2.C");
int i123 = t_1;
int j123 = t_2;
t_1 = 3;
}

fails with:

/Users/pcanal/root_working/code/master/roottest/cling/return/./trun.C:7:1: warning: declaration without the 'auto' keyword is deprecated: function '__cling_Un1Qu30' [-Wdeprecated-declarations]
t_1 = 3;
^~~
auto 
input_line_11:2:3: error: reference to 't_1' is ambiguous
 (t_1)
  ^
/Users/pcanal/root_working/code/master/roottest/cling/return/t1.C:1:5: note: candidate found by name lookup is 't_1'
int t_1 = 3;
    ^
/Users/pcanal/root_working/code/master/roottest/cling/return/./trun.C:7:1: note: candidate found by name lookup is '__cling_N50::t_1'
t_1 = 3;
^
input_line_11:2:3: error: unknown type name 't_1'
 (t_1)
  ^

[hahnjo]

I personally don't think this should block the 6.32 release: As far as I understand, this has basically always been broken in Cling, and I verified that constRetrunTest_WILL_FAIL doesn't pass either on 6.20 using LLVM 5:

1079: Processing /home/jhahnfel/ROOT/v6-20-00-patches/src/roottest/cling/return/run.C...
1079: /home/jhahnfel/ROOT/v6-20-00-patches/src/roottest/cling/return/run.C:7:4: error: expected ';' after expression
1079: t02 t;
1079:    ^
1079:    ;
1079: /home/jhahnfel/ROOT/v6-20-00-patches/src/roottest/cling/return/run.C:7:5: error: use of undeclared identifier 't'
1079: t02 t;
1079:     ^
1079: /home/jhahnfel/ROOT/v6-20-00-patches/src/roottest/cling/return/run.C:8:15: error: use of undeclared identifier 't'
1079: TObject o = **t.getVal();
1079:               ^
1079: /home/jhahnfel/ROOT/v6-20-00-patches/src/roottest/cling/return/run.C:9:24: error: use of undeclared identifier 't'
1079: TObject * const * op = t.getVal();
1079:                        ^

[pcanal]

Will_Fail is the (now) expected result and lead to a 'succesfull' run of the test. What is "new" is that there is one platform where this failure is now a segmentation fault of sort.