[llvm-bugs] [Bug 36132] New: Nested Template Visibility is Not Right

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36132

            Bug ID: 36132
           Summary: Nested Template Visibility is Not Right
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: bluechristlove at 163.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org

Code:

#define HIDDEN __attribute__((visibility("hidden")))
#define PROTECTED __attribute__((visibility("protected")))
#define DEFAULT __attribute__((visibility("default")))
template <typename T> class HIDDEN C {
public:
  template <typename U> class PROTECTED D {
  public:
    void f();
  };
};

int main() {
  C<int>::D<int> d;
  d.f();
}

When we compile it and dump the symbol proporty:

Symbol table '.symtab' contains 6 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS c.C
     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    2
     3: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND .TOC.
     4: 0000000000000000     0 NOTYPE  GLOBAL HIDDEN   UND C<int>::D<int>::f()
     5: 0000000000000000    76 FUNC    GLOBAL DEFAULT [<localentry>: 8]     2
main

We can see that function's visibility is HIDDEN. But it should belongs to D's
visibility: PROTECTED.

When we use GCC:
Symbol table '.symtab' contains 12 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS c.C
     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1
     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    3
     4: 0000000000000000     0 SECTION LOCAL  DEFAULT    4
     5: 0000000000000000     0 SECTION LOCAL  DEFAULT    5
     6: 0000000000000000     0 SECTION LOCAL  DEFAULT    7
     7: 0000000000000000     0 SECTION LOCAL  DEFAULT    8
     8: 0000000000000000     0 SECTION LOCAL  DEFAULT    6
     9: 0000000000000000    84 FUNC    GLOBAL DEFAULT [<localentry>: 8]     1
main
    10: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND .TOC.
    11: 0000000000000000     0 NOTYPE  GLOBAL PROTECTED  UND
C<int>::D<int>::f()
We can see that GCC's behaviour is right.

Additionally, if we don't use nested template, i.e.

#define HIDDEN __attribute__((visibility("hidden")))
#define PROTECTED __attribute__((visibility("protected")))
#define DEFAULT __attribute__((visibility("default")))
  template<typename T>
  class HIDDEN C {
public:
    class PROTECTED D {
public:
      void f();
    };
  };

int main() {
  C<int>::D d;
  d.f();
}

Clang can get the right visibility.

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