bpo-37926: Fix PySys_SetArgvEx(0, NULL, 0) crash (GH-15415) (GH-15420)

empty_argv is no longer static in Python 3.8, but it is declared in
a temporary scope, whereas argv keeps a reference to it.
empty_argv memory (allocated on the stack) is reused by
make_sys_argv() code which is inlined when using gcc -O3.

Define empty_argv in PySys_SetArgvEx() body, to ensure
that it remains valid for the whole lifetime of
the PySys_SetArgvEx() call.

(cherry picked from commit c48682509dc49b43fe914fe6c502bc390345d1c2)

diff --git a/Misc/NEWS.d/next/C API/2019-08-23-11-35-55.bpo-37926.hnI5IQ.rst b/Misc/NEWS.d/next/C API/2019-08-23-11-35-55.bpo-37926.hnI5IQ.rst
new file mode 100644 (file)
index 0000000..2018533
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2019-08-23-11-35-55.bpo-37926.hnI5IQ.rst
@@ -0,0 +1 @@
+Fix a crash in ``PySys_SetArgvEx(0, NULL, 0)``.

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 6a49d8992324087d5b1d44ad261e25e548085ab5..577b6fbbc752a652fc55c2e5753ab53dfb7870ca 100644 (file)
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -3080,9 +3080,10 @@ make_sys_argv(int argc, wchar_t * const * argv)
 void
 PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath)
 {
+    wchar_t* empty_argv[1] = {L""};
+
     if (argc < 1 || argv == NULL) {
         /* Ensure at least one (empty) argument is seen */
-        wchar_t* empty_argv[1] = {L""};
         argv = empty_argv;
         argc = 1;
     }