[llvm] [clang-tools-extra] [flang] [clang] [flang] GETLOG runtime and extension implementation: get login username (PR #74628)

[Yi Wu via cfe-commits]

yi-wu-arm wrote:

> 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](https://github.com/llvm/llvm-project/files/13887475/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?

https://github.com/llvm/llvm-project/pull/74628