2015-05-01 20:22 GMT+02:00 Jonathan Wakely <jwak...@redhat.com>: > On 01/05/15 19:03 +0200, Daniel Krügler wrote: >> >> b/libstdc++-v3/src/filesystem/path.cc: >> >> - path::compare(const path& p) const noexcept: >> >> Shouldn't the implementation of this noexcept function not try to >> create copies of path objects? Couldn't _Cmpt just hold references to >> _M_pathname? > > All your other comments are definitely correct and I'll make the > relevant fixes soon, but I'm not sure what you mean here, could you > clarify?
My remembrance of the difference in noexcept qualifications of int compare(const path& p) const noexcept; int compare(const string_type& s) const; int compare(const value_type* s) const; is that the latter are allowed to allocate memory to be implemented as the standard writes the corresponding functions for std::basic_string: int compare(const basic_string& str) const noexcept; int compare(const charT* s) const; Returns: compare(basic_string(s)). But if I read your implementation of path::compare(const path& p) correctly it *also* may allocate memory by copying _M_pathname into a _Cmpt object. I was wondering whether for this comparison there exists real need to *copy* _M_pathname (potentially exceeding the memory limits). Wouldn't it be possible to define a _CmptRef type that for the purpose of implementing compare(const path& p) just refers to references of the _M_pathname and therefore doesn't need to allocate any dynamic storage? (I should have spoken of a new type _CmptRef and not of your existing _Cmpt). > I think it would be possible to implement a path like: Actually I was not (yet) suggesting to change your API of path, I was only wondering whether given the existing ABI compare(const path& p) could be implementable without need of additional dynamic memory. This was more a kind of louder thinking, I have not fully thought whether this not possible without changing your currently suggested ABI. - Daniel
