use a fresh timeval variable for select(2) portability

picnixz · picnixz · commit 2996937efc49 · 2024-12-27T12:04:02.000+01:00
diff --git a/Modules/timemodule.c b/Modules/timemodule.c
@@ -2407,15 +2407,23 @@ pysleep(PyTime_t timeout)
 static int
 pysleep_zero_posix(void)
 {
-    static struct timeval zero = {0, 0};
-
     PyTime_t deadline, monotonic;
     if (PyTime_Monotonic(&monotonic) < 0) {
         return -1;
     }
     deadline = monotonic;
     do {
         int ret, err;
+        // POSIX-compliant select(2) allows the 'timeout' parameter to
+        // be modified but also mandates that the function should return
+        // immediately if *both* structure's fields are zero (which is
+        // the case here).
+        //
+        // However, since System V (but not BSD) variant typically sets
+        // the timeout before returning (but does not specify whether
+        // this is also the case for zero timeouts), we prefer supplying
+        // a fresh timeout everytime.
+        struct timeval zero = {0, 0};
         Py_BEGIN_ALLOW_THREADS
         ret = select(0, (fd_set *)0, (fd_set *)0, (fd_set *)0, &zero);
         err = errno;
diff --git a/Tools/c-analyzer/cpython/ignored.tsv b/Tools/c-analyzer/cpython/ignored.tsv
@@ -313,7 +313,6 @@ Modules/pyexpat.c	-	error_info_of	-
 Modules/pyexpat.c	-	handler_info	-
 Modules/termios.c	-	termios_constants	-
 Modules/timemodule.c	init_timezone	YEAR	-
-Modules/timemodule.c	pysleep_zero_posix	zero	-
 Objects/bytearrayobject.c	-	_PyByteArray_empty_string	-
 Objects/complexobject.c	-	c_1	-
 Objects/exceptions.c	-	static_exceptions	-
