_PepUnicode_AsString: Fix a broken promise

This function was optimized in an incompatible way.
It does not work when the string argument is short-lived.

But: It was found that the equivalent function without Limited API
does not survive short-lived arguments, either. So the broken promise
was still there, but in a different way than assumed ;-)

Fortunately, the replacement function PyUnicode_AsUTF8 is part
of the Limited API since Python 3.10 and we can avoid this hack.
Unfortunately, there is no way to know which runtime-version
this will be, and we must wait until Python 3.10 becomes the
minimum version :(

Change-Id: Id2b1ea3212984a69bef8d71a578825978c59947e
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
(cherry picked from commit a8004df5a920e02a783d896af33bb83619492b02)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 16 insertions, 11 deletions

diff --git a/sources/shiboken6/libshiboken/pep384impl.cpp b/sources/shiboken6/libshiboken/pep384impl.cpp
index 0b9e901f9..3a9a60f74 100644
--- a/sources/shiboken6/libshiboken/pep384impl.cpp
+++ b/sources/shiboken6/libshiboken/pep384impl.cpp
@@ -345,11 +345,12 @@ static const char *utf8FastPath(PyObject *str)
 const char *_PepUnicode_AsString(PyObject *str)
 {
     /*
-     * We need to keep the string alive but cannot borrow the Python object.
-     * Ugly easy way out: We re-code as an interned bytes string. This
-     * produces a pseudo-leak as long as there are new strings.
-     * Typically, this function is used for name strings, and the dict size
-     * will not grow so much.
+     * This function is the surrogate for PyUnicode_AsUTF8, which keeps the data
+     * in the unicode object as long as that object exists.
+     *
+     * The function does too much if not optimized by utf8, because it keeps the
+     * string alive, unconditionally.
+     * We should not rely on this behavior and think of PyUnicode_AsUTF8, only.
      */
 #define STRINGIFY(x) #x
 #define TOSTRING(x) STRINGIFY(x)
diff --git a/sources/shiboken6/libshiboken/pep384impl.h b/sources/shiboken6/libshiboken/pep384impl.h
index 05743fbba..07cdb3a6f 100644
--- a/sources/shiboken6/libshiboken/pep384impl.h
+++ b/sources/shiboken6/libshiboken/pep384impl.h
@@ -193,6 +193,9 @@ LIBSHIBOKEN_API int Pep_GetVerboseFlag(void);
 // PyUnicode_GetSize is deprecated in favor of PyUnicode_GetLength.
 #define PepUnicode_GetLength(op)    PyUnicode_GetLength((PyObject *)(op))
 
+// Unfortunately, we cannot ask this at runtime
+// #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030A0000
+// FIXME: Python 3.10: Replace _PepUnicode_AsString by PyUnicode_AsUTF8
 #ifdef Py_LIMITED_API
 
 LIBSHIBOKEN_API const char *_PepUnicode_AsString(PyObject *);
diff --git a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/parser.py b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/parser.py
index dc62aa724..be82a4f92 100644
--- a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/parser.py
+++ b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/parser.py
@@ -69,18 +69,19 @@ def _get_flag_enum_option():
         flag = getattr(sys, sysname)
         if not isinstance(flag, int):
             flag = True
+    p = f"\n    *** Python is at version {'.'.join(map(str, pyminver))} now."
     # PYSIDE-1797: Emit a warning when we may remove pep384_issue33738.cpp
     if pyminver and pyminver >= (3, 8):
-        warnings.warn(f"\n    *** Python is at version {'.'.join(map(str, pyminver))} now. "
-                      f"The file pep384_issue33738.cpp should be removed ASAP! ***")
+        warnings.warn(f"{p} The file pep384_issue33738.cpp should be removed ASAP! ***")
+    # _PepUnicode_AsString: Fix a broken promise
+    if pyminver and pyminver >= (3, 10):
+        warnings.warn(f"{p} _PepUnicode_AsString can now be replaced by PyUnicode_AsUTF8! ***")
     # PYSIDE-1960: Emit a warning when we may remove pep384_issue33738.cpp
     if pyminver and pyminver >= (3, 11):
-        warnings.warn(f"\n    *** Python is at version {'.'.join(map(str, pyminver))} now. "
-                      f"The files bufferprocs_py37.(cpp|h) should be removed ASAP! ***")
+        warnings.warn(f"{p} The files bufferprocs_py37.(cpp|h) should be removed ASAP! ***")
     # PYSIDE-1735: Emit a warning when we should maybe evict forgiveness mode
     if ver[:2] >= (7, 0):
-        warnings.warn(f"\n    *** PySide is at version {'.'.join(map(str, ver[:2]))} now. "
-                      f"Please drop the forgiving Enum behavior in `mangled_type_getattro` ***")
+        warnings.warn(f"{p} Please drop Enum forgiveness mode in `mangled_type_getattro` ***")
     # normalize the sys attribute
     setattr(sys, sysname, flag)
     os.environ[envname] = str(flag)