gh-113343: Fix error check on mmap(2) (#113342)

Fix error check on mmap(2)

It should check MAP_FAILED instead of NULL for error.

On mmap(2) man page:

  RETURN VALUE
       On success, mmap() returns a pointer to the mapped area.
       On error, the value MAP_FAILED (that is, (void *) -1) is
       returned, and errno is set to indicate the error.

diff --git a/Python/perf_trampoline.c b/Python/perf_trampoline.c
index 540b650192ed34fd4ea58890352e862d72818d82..750ba18d3510ed529baa2a8eb90d72db6c613880 100644 (file)
--- a/Python/perf_trampoline.c
+++ b/Python/perf_trampoline.c
@@ -247,7 +247,7 @@ new_code_arena(void)
              mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS,
              -1,  // fd (not used here)
              0);  // offset (not used here)
-    if (!memory) {
+    if (memory == MAP_FAILED) {
         PyErr_SetFromErrno(PyExc_OSError);
         PyErr_FormatUnraisable("Failed to create new mmap for perf trampoline");
         perf_status = PERF_STATUS_FAILED;