[LLVMbugs] [Bug 8450] New: Unexpected error "explicit specialization of 'XXX' after instantiation

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Oct 24 05:26:50 PDT 2010


           Summary: Unexpected error "explicit specialization of 'XXX'
                    after instantiation
           Product: clang
           Version: trunk
          Platform: Other
        OS/Version: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: kiyolee at hotmail.com
                CC: llvmbugs at cs.uiuc.edu, dgregor at apple.com

Consider the following 2 source files:

// llvm-bug.h
#include <cstdlib>
template<class _Elem>
class MyClass {
   static const signed char tbl[256];
   static int lookup(const _Elem& c) {
      return (c >= 0 && (size_t)c < sizeof(tbl)/sizeof(tbl[0]))
         ? tbl[(size_t)c] : -1;
const signed char MyClass<char>::tbl[256];
int MyClass<char>::lookup(const char& c)
   return MyClass<char>::tbl[(unsigned char)c];
// eof

// llvm-bug.cpp
#include "llvm-bug.h"
const signed char MyClass<char>::tbl[256] = { 0 };
// eof

Compiling llvm-bug.cpp without the WORKAROUND block would report the following

llvm-bug.cpp:4:34: error: explicit specialization of 'tbl' after instantiation
const signed char MyClass<char>::tbl[256] = { 0 };
In file included from llvm-bug.cpp:3:
./llvm-bug.h:19:26: note: implicit instantiation first required here
   return MyClass<char>::tbl[(unsigned char)c];
1 error generated.

The file would be compiled alright if WORKAROUND block is included and that
does not seem actually correct.
For comparison, g++ accept both with and without the WORKAROUND block.
VC 2008 would report error for the WORKAROUND block instead about member
variable without initializer but initializer in header is wrong either:
duplicate copies of the same static member variable upon linking if the header
is used by multiple .cpp files.

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