[Bug c++/85461] New: A simple recursive TMP static const initializer defeats gcc

[zhonghao at pku dot org.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85461

            Bug ID: 85461
           Summary: A simple recursive TMP static const initializer
                    defeats gcc
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhonghao at pku dot org.cn
  Target Milestone: ---

The test case is as follow:

template<unsigned int v>
class bitWidthHolding {
public:
    /** width is the number of bits occupied by the template parameter v
        */
    static const
    unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width + 1);
};

clang++ compiles the code, but gcc produces errors:

../1Testprogramtoillustratetheproblembuiltwithclang-ctestit.cpp: In
instantiation of ‘const unsigned int bitWidthHolding<0>::width’:
../1Testprogramtoillustratetheproblembuiltwithclang-ctestit.cpp:7:73:  
recursively required from ‘const unsigned int bitWidthHolding<127>::width’
../1Testprogramtoillustratetheproblembuiltwithclang-ctestit.cpp:7:73:  
required from ‘const unsigned int bitWidthHolding<255>::width’
../1Testprogramtoillustratetheproblembuiltwithclang-ctestit.cpp:10:46:  
required from here
../1Testprogramtoillustratetheproblembuiltwithclang-ctestit.cpp:7:73: fatal
error: template instantiation depth exceeds maximum of 900 (use
-ftemplate-depth= to increase the maximum)
         unsigned int width = (v == 0 ? 0 : bitWidthHolding<(v >> 1)>::width +
1);
                                           
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~

A bug report from clang (https://bugs.llvm.org/show_bug.cgi?id=9999) explains
some details.