gh-112970: Detect and use closefrom() when available (#112969)

thesamesam · web-flow · commit c454e934d361 · 2023-12-12T11:25:27.000+01:00
glibc-2.34 implements closefrom(3) using the same semantics as on BSD.
Check for closefrom() in configure and use the check result in
fileutils.c, rather than hardcoding a FreeBSD check.

Some implementations of closefrom() return an int. Explicitly discard 
the return value by casting it to void, to avoid future compiler
warnings.

Signed-off-by: Sam James &lt;sam@gentoo.org&gt;
diff --git a/Misc/NEWS.d/next/Library/2023-12-11-16-13-15.gh-issue-112970.87jmKP.rst b/Misc/NEWS.d/next/Library/2023-12-11-16-13-15.gh-issue-112970.87jmKP.rst
@@ -0,0 +1 @@
+Use :c:func:`!closefrom` on Linux where available (e.g. glibc-2.34), rather than only FreeBSD.
diff --git a/Python/fileutils.c b/Python/fileutils.c
@@ -2878,9 +2878,9 @@ _Py_GetLocaleconvNumeric(struct lconv *lc,
  *    non-opened fd in the middle.
  * 2b. If fdwalk(3) isn't available, just do a plain close(2) loop.
  */
-#ifdef __FreeBSD__
+#ifdef HAVE_CLOSEFROM
 #  define USE_CLOSEFROM
-#endif /* __FreeBSD__ */
+#endif /* HAVE_CLOSEFROM */
 
 #ifdef HAVE_FDWALK
 #  define USE_FDWALK
@@ -2922,7 +2922,7 @@ _Py_closerange(int first, int last)
 #ifdef USE_CLOSEFROM
     if (last >= sysconf(_SC_OPEN_MAX)) {
         /* Any errors encountered while closing file descriptors are ignored */
-        closefrom(first);
+        (void)closefrom(first);
     }
     else
 #endif /* USE_CLOSEFROM */
diff --git a/configure b/configure
diff --git a/configure.ac b/configure.ac
@@ -4745,7 +4745,7 @@ fi
 
 # checks for library functions
 AC_CHECK_FUNCS([ \
-  accept4 alarm bind_textdomain_codeset chmod chown clock close_range confstr \
+  accept4 alarm bind_textdomain_codeset chmod chown clock closefrom close_range confstr \
   copy_file_range ctermid dup dup3 execv explicit_bzero explicit_memset \
   faccessat fchmod fchmodat fchown fchownat fdopendir fdwalk fexecve \
   fork fork1 fpathconf fstatat ftime ftruncate futimens futimes futimesat \
diff --git a/pyconfig.h.in b/pyconfig.h.in
@@ -157,6 +157,9 @@
 /* Define to 1 if you have the `clock_settime' function. */
 #undef HAVE_CLOCK_SETTIME
 
+/* Define to 1 if you have the `closefrom' function. */
+#undef HAVE_CLOSEFROM
+
 /* Define to 1 if you have the `close_range' function. */
 #undef HAVE_CLOSE_RANGE
 
