bpo-37369: Fix initialization of sys members when launched via an app container (GH-14467)

sys._base_executable is now always defined on all platforms, and can be overridden through configuration.
Also adds test.support.PythonSymlink to encapsulate platform-specific logic for symlinking sys.executable

2 files changed, 7 insertions, 4 deletions

diff --git a/Include/cpython/initconfig.h b/Include/cpython/initconfig.h
index 67f38e2..297fbf7 100644
--- a/Include/cpython/initconfig.h
+++ b/Include/cpython/initconfig.h
@@ -373,10 +373,11 @@ typedef struct {
                                        module_search_paths_set is equal
                                        to zero. */
 
-    wchar_t *executable;    /* sys.executable */
-    wchar_t *prefix;        /* sys.prefix */
-    wchar_t *base_prefix;   /* sys.base_prefix */
-    wchar_t *exec_prefix;   /* sys.exec_prefix */
+    wchar_t *executable;        /* sys.executable */
+    wchar_t *base_executable;   /* sys._base_executable */
+    wchar_t *prefix;            /* sys.prefix */
+    wchar_t *base_prefix;       /* sys.base_prefix */
+    wchar_t *exec_prefix;       /* sys.exec_prefix */
     wchar_t *base_exec_prefix;  /* sys.base_exec_prefix */
 
     /* --- Parameter only used by Py_Main() ---------- */
diff --git a/Include/internal/pycore_pathconfig.h b/Include/internal/pycore_pathconfig.h
index be12c6f..9e0ba0b 100644
--- a/Include/internal/pycore_pathconfig.h
+++ b/Include/internal/pycore_pathconfig.h
@@ -27,6 +27,8 @@ typedef struct _PyPathConfig {
        are ignored when their value are equal to -1 (unset). */
     int isolated;
     int site_import;
+    /* Set when a venv is detected */
+    wchar_t *base_executable;
 } _PyPathConfig;
 
 #define _PyPathConfig_INIT \