Re: [PATCH v2] win32: don't force _WIN32_WINNT to a lower version

[Steve Lhomme]

On 2020-05-28 2:12, Bruno Haible wrote:
Hi Steve,

Hi Bruno,

When building for UWP it's particularly important as a lot of APIs may
be hidden if you use the proper values and they are hidden because you
shouldn't use them. Forcing to use them when they shouldn't will lead to
apps that don't run.

Oh, so Microsoft is not only adding new APIs from one version to the next,
but sometimes also removing APIs. Indeed, the Microsoft doc says this:

   "Over the years, Windows APIs and data types have been added, and
    sometimes changed or removed."

<https://docs.microsoft.com/en-us/cpp/porting/overview-of-potential-upgrade-issues-visual-cpp>

I've never been hit by an API removal. But with UWP and win10 variants 
they made a set of API's available on all devices but not all of them 
(the full API set is left on Desktop, for now). So apps targeting *all* 
win10 devices should restrict to these API's.

https://docs.microsoft.com/en-us/uwp/win32-and-com/win32-apis

Applied like this. (I couldn't take your patch as-is, because in Gnulib
we indent preprocessor lines in a particular way.)

Thanks a lot.

2020-05-27  Bruno Haible  <br...@clisp.org>

        Improve pattern for defining _WIN32_WINNT.
        Newer versions of the Windows API may not only add, but also remove API
        functions. Therefore, when the user is e.g. building for Windows 10, we
        should not set _WIN32_WINNT to e.g. Windows 8, as this may enable the
        use of APIs that were present in Windows 8 but removed in Windows 10.
        Suggested by Steve Lhomme <rob...@ycbcr.xyz> in
        <https://lists.gnu.org/archive/html/bug-gnulib/2020-05/msg00318.html>.
        * lib/ftruncate.c (_WIN32_WINNT): Don't set to a smaller value.
        * lib/sethostname.c (_WIN32_WINNT): Likewise.
        * lib/stat-w32.c (_WIN32_WINNT): Likewise.

diff --git a/lib/ftruncate.c b/lib/ftruncate.c
index a185637..2514075 100644
--- a/lib/ftruncate.c
+++ b/lib/ftruncate.c
@@ -30,8 +30,10 @@
     argument.  So, define a 64-bit safe SetFileSize function ourselves.  */
  
  /* Ensure that <windows.h> declares GetFileSizeEx.  */
-#  undef _WIN32_WINNT
-#  define _WIN32_WINNT _WIN32_WINNT_WIN2K
+#  if !defined _WIN32_WINNT || (_WIN32_WINNT < _WIN32_WINNT_WIN2K)
+#   undef _WIN32_WINNT
+#   define _WIN32_WINNT _WIN32_WINNT_WIN2K
+#  endif
  
  /* Get declarations of the native Windows API functions.  */
  #  define WIN32_LEAN_AND_MEAN
diff --git a/lib/sethostname.c b/lib/sethostname.c
index 1be69be..96318fb 100644
--- a/lib/sethostname.c
+++ b/lib/sethostname.c
@@ -23,11 +23,11 @@
  /* Unix API.  */
  
  /* Specification.  */
-#include <unistd.h>
+# include <unistd.h>
  
-#include <errno.h>
-#include <stdio.h>
-#include <limits.h>
+# include <errno.h>
+# include <stdio.h>
+# include <limits.h>
  
  /* Set up to LEN chars of NAME as system hostname.
     Return 0 if ok, set errno and return -1 on error. */
@@ -43,7 +43,7 @@ sethostname (const char *name, size_t len)
        return -1;
      }
  
-#ifdef __minix /* Minix */
+# ifdef __minix /* Minix */
    {
      FILE *hostf;
      int r = 0;
@@ -76,38 +76,40 @@ sethostname (const char *name, size_t len)
  
      return r;
    }
-#else
+# else
    /* For platforms that we don't have a better option for, simply bail
       out.  */
    errno = ENOSYS;
    return -1;
-#endif
+# endif
  }
  
  #else
  /* Native Windows API.  Also used on Cygwin.  */
  
  /* Ensure that <windows.h> declares SetComputerNameEx.  */
-#undef _WIN32_WINNT
-#define _WIN32_WINNT _WIN32_WINNT_WIN2K
+# if !defined _WIN32_WINNT || (_WIN32_WINNT < _WIN32_WINNT_WIN2K)
+#  undef _WIN32_WINNT
+#  define _WIN32_WINNT _WIN32_WINNT_WIN2K
+# endif
  
-#define WIN32_LEAN_AND_MEAN
+# define WIN32_LEAN_AND_MEAN
  
  /* Specification.  */
-#include <unistd.h>
+# include <unistd.h>
  
-#include <errno.h>
-#include <limits.h>
-#include <string.h>
+# include <errno.h>
+# include <limits.h>
+# include <string.h>
  
-#include <windows.h>
+# include <windows.h>
  /* The mingw header files don't define GetComputerNameEx, SetComputerNameEx.  
*/
-#ifndef GetComputerNameEx
-# define GetComputerNameEx GetComputerNameExA
-#endif
-#ifndef SetComputerNameEx
-# define SetComputerNameEx SetComputerNameExA
-#endif
+# ifndef GetComputerNameEx
+#  define GetComputerNameEx GetComputerNameExA
+# endif
+# ifndef SetComputerNameEx
+#  define SetComputerNameEx SetComputerNameExA
+# endif
  
  /* Set up to LEN chars of NAME as system hostname.
     Return 0 if ok, set errno and return -1 on error. */
diff --git a/lib/stat-w32.c b/lib/stat-w32.c
index 296ccf1..c4b5de9 100644
--- a/lib/stat-w32.c
+++ b/lib/stat-w32.c
@@ -21,8 +21,10 @@
  #if defined _WIN32 && ! defined __CYGWIN__
  
  /* Ensure that <windows.h> defines FILE_ID_INFO.  */
-#undef _WIN32_WINNT
-#define _WIN32_WINNT _WIN32_WINNT_WIN8
+#if !defined _WIN32_WINNT || (_WIN32_WINNT < _WIN32_WINNT_WIN8)
+# undef _WIN32_WINNT
+# define _WIN32_WINNT _WIN32_WINNT_WIN8
+#endif
  
  #include <sys/types.h>
  #include <sys/stat.h>