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[cling] Decls in an unnamed namespace cannot be looked up after a unload-load cycle #7483

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Axel-Naumann opened this issue Mar 12, 2021 · 0 comments · Fixed by #9998
Closed

[cling] Decls in an unnamed namespace cannot be looked up after a unload-load cycle #7483

Axel-Naumann opened this issue Mar 12, 2021 · 0 comments · Fixed by #9998
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@jalopezg-git
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affects:master bug in:Cling priority:low

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@Axel-Naumann
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Describe the bug

A definition in an unnamed namespace cannot be redeclared by re-running the same code.

Expected behavior

A new declaration is provided; 13 is printed twice.

To Reproduce

// t.cxx
namespace {
  int h = 12;
}

void t() {
  printf("%d\n", ++h);
}
root [0] .x t.cxx
13
root [1] .x t.cxx
In file included from input_line_10:1:
t.cxx:6:20: error: use of undeclared identifier 'h'
  printf("%d\n", ++h);
                   ^

Setup

ROOT master Ubuntu
@jalopezg-git jalopezg-git changed the title Cannot redefine entities in unnamed namespace [cling] Decls in an unnamed namespace cannot be looked up after a unload-load cycle Feb 28, 2022
jalopezg-git added a commit to jalopezg-git/root that referenced this issue Feb 28, 2022
@jalopezg-git
[cling] DeclUnloader: reset the anonymous namespace in the enclosing DC
f43c2cf 
From SemaDeclCXX.cpp:
```
C++ [namespace.unnamed]p1.  An unnamed-namespace-definition behaves as if it
were replaced by
     namespace unique { /* empty body */ }
     using namespace unique;
     namespace unique { namespace-body }
where all occurrences of 'unique' in a translation unit are replaced by the same
identifier and this identifier differs from all other identifiers in the entire
program.
```

Thus, the first declaration of an unnamed namespace creates an implicit
UsingDirectiveDecl that makes the names available in the parent DC.

If we are reverting such first declaration, make sure we reset the anonymous
namespace for the parent DeclContext so that the implicit UsingDirectiveDecl
is created again when parsing the next anonymous namespace.

Fixes issue root-project#7483.
jalopezg-git added a commit to jalopezg-git/root that referenced this issue Feb 28, 2022
@jalopezg-git
[cling] Add test against issue root-project#7483
da78969
jalopezg-git added a commit to jalopezg-git/root that referenced this issue Feb 28, 2022
@jalopezg-git
[cling] DeclUnloader: reset the anonymous namespace in the enclosing DC
653444f 
From SemaDeclCXX.cpp:
```
C++ [namespace.unnamed]p1.  An unnamed-namespace-definition behaves as if it
were replaced by
     namespace unique { /* empty body */ }
     using namespace unique;
     namespace unique { namespace-body }
where all occurrences of 'unique' in a translation unit are replaced by the same
identifier and this identifier differs from all other identifiers in the entire
program.
```

Thus, the first declaration of an unnamed namespace creates an implicit
UsingDirectiveDecl that makes the names available in the parent DC.

If we are reverting such first declaration, make sure we reset the anonymous
namespace for the parent DeclContext so that the implicit UsingDirectiveDecl
is created again when parsing the next anonymous namespace.

Fixes issue root-project#7483.
jalopezg-git added a commit to jalopezg-git/root that referenced this issue Feb 28, 2022
@jalopezg-git
[cling] Add test against issue root-project#7483
47876a4
@jalopezg-git jalopezg-git mentioned this issue Feb 28, 2022
Merged
1 task
jalopezg-git added a commit to jalopezg-git/root that referenced this issue Feb 28, 2022
@jalopezg-git
[cling] DeclUnloader: reset the anonymous namespace in the enclosing DC
551321c 
From SemaDeclCXX.cpp:
```
C++ [namespace.unnamed]p1.  An unnamed-namespace-definition behaves as if it
were replaced by
     namespace unique { /* empty body */ }
     using namespace unique;
     namespace unique { namespace-body }
where all occurrences of 'unique' in a translation unit are replaced by the same
identifier and this identifier differs from all other identifiers in the entire
program.
```

Thus, the first declaration of an unnamed namespace creates an implicit
UsingDirectiveDecl that makes the names available in the parent DC.

If we are reverting such first declaration, make sure we reset the anonymous
namespace for the parent DeclContext so that the implicit UsingDirectiveDecl
is created again when parsing the next anonymous namespace.

Fixes issue root-project#7483.
jalopezg-git added a commit that referenced this issue Mar 1, 2022
@jalopezg-git
[cling] DeclUnloader: reset the anonymous namespace in the enclosing DC
6db6bcd 
From SemaDeclCXX.cpp:
```
C++ [namespace.unnamed]p1.  An unnamed-namespace-definition behaves as if it
were replaced by
     namespace unique { /* empty body */ }
     using namespace unique;
     namespace unique { namespace-body }
where all occurrences of 'unique' in a translation unit are replaced by the same
identifier and this identifier differs from all other identifiers in the entire
program.
```

Thus, the first declaration of an unnamed namespace creates an implicit
UsingDirectiveDecl that makes the names available in the parent DC.

If we are reverting such first declaration, make sure we reset the anonymous
namespace for the parent DeclContext so that the implicit UsingDirectiveDecl
is created again when parsing the next anonymous namespace.

Fixes issue #7483.
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@Axel-Naumann @jalopezg-git