[flang] GETLOG runtime and extension implementation: get login username

[yiwu0b11]

Get login username, ussage:

CHARACTER(32) :: login
CALL getlog(login)
WRITE(*,*) login

getlog is required for an exascale proxyapp.
https://proxyapps.exascaleproject.org/app/minismac2d/
https://github.com/Mantevo/miniSMAC/blob/f90446714226eeef650b78bce06ca4967792e74d/ref/smac2d.f#L615
https://github.com/Mantevo/miniSMAC/blob/f90446714226eeef650b78bce06ca4967792e74d/ref/smac2d.f#L1570

[yiwu0b11]

accidently push the wrong branch in previous pr #70917

[yiwu0b11]

#70917 (comment)
Thanks for the suggestion.
Now it only checks environment variable if there is an error from getlogin_r

[yiwu0b11]

getlog library intrinsic will first retrieve user login name using getlog_r on Linux and GetUserName on Windows. If that returns an error, it will then use environment variable to get username.

[DavidTruby]

LGTM

[yiwu0b11]

Hi @jeanPerier Sorry to throw a ping. I have changed the structure and implementation of getlog, it now does the following:
On Linux: use getlogin_r, if fail get from environment variable.
On Windows: get from environment variable to avoid linking to library Advapi32.lib.
Username will be pad with spaces as how gfortran does it.
e.g.

loginName    XXXXX       <--------- if length is longer than name, pad with space
loginNameXXXX            <--------- just right
logiXXXX                 <--------- if shorter still fill with name

Proper test has been added on both Linux and Windows for getlog_r and environment variable.

[jeanPerier]

Described logic in your comment looks good to me. I have two comments regarding the implementation.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[yiwu0b11]

Windows CI failure: compiler out of heap space.

[rorth]

This patch broke the Solaris build:

FAILED: tools/flang/runtime/CMakeFiles/obj.FortranRuntime.dir/extensions.cpp.o 
[...]
/vol/llvm/src/llvm-project/dist/flang/runtime/extensions.cpp:60:24: error: use of undeclared identifier 'LOGIN_NAME_MAX'
   60 |   const int nameMaxLen{LOGIN_NAME_MAX + 1};
      |                        ^
/vol/llvm/src/llvm-project/dist/flang/runtime/extensions.cpp:61:12: warning: variable length arrays in C++ are a Clang extension [-Wvla-cxx-extension]
   61 |   char str[nameMaxLen];
      |            ^~~~~~~~~~
/vol/llvm/src/llvm-project/dist/flang/runtime/extensions.cpp:61:12: note: initializer of 'nameMaxLen' is unknown
/vol/llvm/src/llvm-project/dist/flang/runtime/extensions.cpp:60:13: note: declared here
   60 |   const int nameMaxLen{LOGIN_NAME_MAX + 1};
      |             ^
1 warning and 1 error generated.

and

FAILED: tools/flang/unittests/Runtime/CMakeFiles/FlangRuntimeTests.dir/CommandTest.cpp.o
[...]
/vol/llvm/src/llvm-project/dist/flang/unittests/Runtime/CommandTest.cpp:530:21: error: use of undeclared identifier 'LOGIN_NAME_MAX' 
  530 |   const int charLen{LOGIN_NAME_MAX + 2};
      |                     ^
/vol/llvm/src/llvm-project/dist/flang/unittests/Runtime/CommandTest.cpp:531:14: warning: variable length arrays in C++ are a Clang extension [-Wvla-cxx-extension]
  531 |   char input[charLen];
      |              ^~~~~~~
/vol/llvm/src/llvm-project/dist/flang/unittests/Runtime/CommandTest.cpp:531:14: note: initializer of 'charLen' is unknown
/vol/llvm/src/llvm-project/dist/flang/unittests/Runtime/CommandTest.cpp:530:13: note: declared here
  530 |   const int charLen{LOGIN_NAME_MAX + 2};
      |             ^

As documented in Solaris limits.h(3HEAD) (and exactly matching XPG7), LOGIN_NAME_MAX not being defined is an allowed configuration:

   Runtime Invariant Values (Possibly Indeterminate)
       A definition of one of the symbolic names  in  the  following  list  is
       omitted  from  <limits.h>  on specific implementations where the corre-
       sponding value is equal to or greater than the stated minimum,  but  is
       unspecified.

       This  indetermination  might  depend  on the amount of available memory
       space on a specific instance of a specific implementation.  The  actual
       value  supported  by  a  specific  instance  will  be  provided  by the
       sysconf() function.
[...]
       LOGIN_NAME_MAX

           Maximum length of a login name.

So the code needs to fall back to sysconf(_SC_LOGIN_NAME_MAX) if LOGIN_NAME_MAX is not defined.

I've used the attached patch to implement this, which allowed the build and ninja check-all to finish. I'm uncertain if support for syscconf() == -1 is really necessary, though.
lnm.txt

[yiwu0b11]

This patch broke the Solaris build:
I've used the attached patch to implement this, which allowed the build and ninja check-all to finish. I'm uncertain if support for syscconf() == -1 is really necessary, though. lnm.txt

Thanks for reporting and providing a fix for this. I do not have a Solaris instance on hand to test it, so if you don't mind, could you send this out as a pull request?

[rorth]

Sure: I've just created one slightly changed from the attached patch: [flang] Handle missing LOGIN_NAME_MAX definition in runtime