vim-patch:8.1.0846: not easy to recognize the system Vim runs on

Problem:    Not easy to recognize the system Vim runs on.
Solution:   Add more items to the features list. (Ozaki Kiichi, closes vim/vim#3855)
https://github.com/vim/vim/commit/39536dd557e847e80572044c2be319db5886abe3

Some doc changes have already been applied. Some others are N/A.
"moon" was removed in patch 8.2.0427 so I did not add it.

3 files changed, 59 insertions, 17 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 29619f62e9..04a1f08f04 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -4433,6 +4433,12 @@ static void f_has(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 #if defined(BSD) && !defined(__APPLE__)
     "bsd",
 #endif
+#ifdef __linux__
+    "linux",
+#endif
+#ifdef SUN_SYSTEM
+    "sun",
+#endif
 #ifdef UNIX
     "unix",
 #endif
diff --git a/src/nvim/testdir/test_functions.vim b/src/nvim/testdir/test_functions.vim
index 0edbeb420a..e4c6c6a3b2 100644
--- a/src/nvim/testdir/test_functions.vim
+++ b/src/nvim/testdir/test_functions.vim
@@ -1377,6 +1377,35 @@ func Test_func_exists_on_reload()
   delfunc ExistingFunction
 endfunc
 
+func Test_platform_name()
+  " The system matches at most only one name.
+  let names = ['amiga', 'beos', 'bsd', 'hpux', 'linux', 'mac', 'qnx', 'sun', 'vms', 'win32', 'win32unix']
+  call assert_inrange(0, 1, len(filter(copy(names), 'has(v:val)')))
+
+  " Is Unix?
+  call assert_equal(has('beos'), has('beos') && has('unix'))
+  call assert_equal(has('bsd'), has('bsd') && has('unix'))
+  call assert_equal(has('hpux'), has('hpux') && has('unix'))
+  call assert_equal(has('linux'), has('linux') && has('unix'))
+  call assert_equal(has('mac'), has('mac') && has('unix'))
+  call assert_equal(has('qnx'), has('qnx') && has('unix'))
+  call assert_equal(has('sun'), has('sun') && has('unix'))
+  call assert_equal(has('win32'), has('win32') && !has('unix'))
+  call assert_equal(has('win32unix'), has('win32unix') && has('unix'))
+
+  if has('unix') && executable('uname')
+    let uname = system('uname')
+    call assert_equal(uname =~? 'BeOS', has('beos'))
+    call assert_equal(uname =~? 'BSD\|DragonFly', has('bsd'))
+    call assert_equal(uname =~? 'HP-UX', has('hpux'))
+    call assert_equal(uname =~? 'Linux', has('linux'))
+    call assert_equal(uname =~? 'Darwin', has('mac'))
+    call assert_equal(uname =~? 'QNX', has('qnx'))
+    call assert_equal(uname =~? 'SunOS', has('sun'))
+    call assert_equal(uname =~? 'CYGWIN\|MSYS', has('win32unix'))
+  endif
+endfunc
+
 sandbox function Fsandbox()
   normal ix
 endfunc
@@ -1519,24 +1548,31 @@ func Test_libcall_libcallnr()
     let libc = 'msvcrt.dll'
   elseif has('mac')
     let libc = 'libSystem.B.dylib'
-  elseif system('uname -s') =~ 'SunOS'
-    " Set the path to libc.so according to the architecture.
-    let test_bits = system('file ' . GetVimProg())
-    let test_arch = system('uname -p')
-    if test_bits =~ '64-bit' && test_arch =~ 'sparc'
-      let libc = '/usr/lib/sparcv9/libc.so'
-    elseif test_bits =~ '64-bit' && test_arch =~ 'i386'
-      let libc = '/usr/lib/amd64/libc.so'
+  elseif executable('ldd')
+    let libc = matchstr(split(system('ldd ' . GetVimProg())), '/libc\.so\>')
+  endif
+  if get(l:, 'libc', '') ==# ''
+    " On Unix, libc.so can be in various places.
+    if has('linux')
+      " There is not documented but regarding the 1st argument of glibc's
+      " dlopen an empty string and nullptr are equivalent, so using an empty
+      " string for the 1st argument of libcall allows to call functions.
+      let libc = ''
+    elseif has('sun')
+      " Set the path to libc.so according to the architecture.
+      let test_bits = system('file ' . GetVimProg())
+      let test_arch = system('uname -p')
+      if test_bits =~ '64-bit' && test_arch =~ 'sparc'
+        let libc = '/usr/lib/sparcv9/libc.so'
+      elseif test_bits =~ '64-bit' && test_arch =~ 'i386'
+        let libc = '/usr/lib/amd64/libc.so'
+      else
+        let libc = '/usr/lib/libc.so'
+      endif
     else
-      let libc = '/usr/lib/libc.so'
+      " Unfortunately skip this test until a good way is found.
+      return
     endif
-  elseif system('uname -s') =~ 'OpenBSD'
-    let libc = 'libc.so'
-  else
-    " On Unix, libc.so can be in various places.
-    " Interestingly, using an empty string for the 1st argument of libcall
-    " allows to call functions from libc which is not documented.
-    let libc = ''
   endif
 
   if has('win32')
diff --git a/src/nvim/testdir/test_writefile.vim b/src/nvim/testdir/test_writefile.vim
index aa7882d129..5ffbe82082 100644
--- a/src/nvim/testdir/test_writefile.vim
+++ b/src/nvim/testdir/test_writefile.vim
@@ -43,7 +43,7 @@ func Test_writefile_fails_gently()
 endfunc
 
 func Test_writefile_fails_conversion()
-  if !has('iconv') || system('uname -s') =~ 'SunOS'
+  if !has('iconv') || has('sun')
     return
   endif
   " Without a backup file the write won't happen if there is a conversion