Compilation failure with C++17 standard

[amadio]

The struct data in voms/voms_api.h clashes with std::data from C++17, and causes the compilation error below:

/usr/include/voms/voms_api.h:115:19: error: template argument 1 is invalid
  115 |   std::vector<data> std;   /*!< User's characteristics */
      |                   ^
/usr/include/voms/voms_api.h:115:19: error: template argument 2 is invalid

This bug has been found after trying to compile XRootD with support for voms with C++17 standard. The build error can be seen here.

A potential fix is to use std::vector<::data> to disambiguate, but it's also probable that std as the variable name will have to be changed as well to avoid further name clashes with the standard C++ namespace std::.

[giacomini]

I have reproduced it at https://godbolt.org/z/c3e14ze9M.
Naming in VOMS is awful, but I am reluctant to make naming changes, unless there are no other solutions. However I suspect the compilation error you see is rather due to the use of using namespace std somewhere in XRootD code; I've seen several occurrences, even in header files.
In the same godbolt above you can also find an easy fix that you can apply, thanks to a well-placed using Data = ::data;. Even better, you can simply use auto dat = (*i).std;.
Let me know.

[amadio]

I think you are right, I searched a bit further and found a using namespace std; in XrdOucString.hh which may be the cause of the clash, as it may be indirectly included in that source file. I will try to fix this on our end first, but it's probably not a bad idea to qualify data as ::data in voms headers anyway.

[giacomini]

I thought a bit more about it and indeed it would be good to qualify data in the VOMS codebase, otherwise it would break if a previously-included header file does using namespace std;.
Thanks for catching this.

[amadio]

I've fixed this on our end, so please feel free to close this ticket anytime if you want. There's no bug in VOMS.

[amadio]

Closing, as there's no bug to actually be fixed in VOMS. Thank you!