PEP 768: Add some clarifications and minor edits

Author: pablogsal

peps/pep-0768.rst

@@ -136,19 +136,20 @@ A new structure is added to PyThreadState to support remote debugging:
 
     typedef struct _remote_debugger_support {
         int debugger_pending_call;
-        char debugger_script[MAX_SCRIPT_SIZE];
+        char debugger_script_path[MAX_SCRIPT_SIZE];
     } _PyRemoteDebuggerSupport;
 
 
 This structure is appended to ``PyThreadState``, adding only a few fields that
 are **never accessed during normal execution**. The ``debugger_pending_call`` field
-indicates when a debugger has requested execution, while ``debugger_script``
-provides Python code to be executed when the interpreter reaches a safe point.
+indicates when a debugger has requested execution, while ``debugger_script_path``
+provides a filesystem path to a Python source file (.py) that will be executed when 
+the interpreter reaches a safe point. The path must point to a Python source file, 
+not compiled Python code (.pyc) or any other format.
 
 The value for ``MAX_SCRIPT_SIZE`` will be a trade-off between binary size and
-how big debugging scripts can be. As most of the logic should be in libraries
-and arbitrary code can be executed with very short amount of Python we are
-proposing to start with 4kb initially. This value can be extended in the future
+how long the path can be. As most paths are relatively short on modern systems, 
+we are proposing to start with 4kb initially. This value can be extended in the future
 if we ever need to.
 
 
@@ -171,13 +172,13 @@ debugger support:
         uint64_t eval_breaker;            // Location of the eval breaker flag
         uint64_t remote_debugger_support; // Offset to our support structure
         uint64_t debugger_pending_call;   // Where to write the pending flag
-        uint64_t debugger_script;         // Where to write the script path
+        uint64_t debugger_script_path;    // Where to write the script path
     } debugger_support;
 
 These offsets allow debuggers to locate critical debugging control structures in
 the target process's memory space. The ``eval_breaker`` and ``remote_debugger_support``
 offsets are relative to each ``PyThreadState``, while the ``debugger_pending_call``
-and ``debugger_script`` offsets are relative to each ``_PyRemoteDebuggerSupport``
+and ``debugger_script_path`` offsets are relative to each ``_PyRemoteDebuggerSupport``
 structure, allowing the new structure and its fields to be found regardless of
 where they are in memory.
 
@@ -199,13 +200,19 @@ When a debugger wants to attach to a Python process, it follows these steps:
 
 5. Write control information:
 
-   - Write a filename containing Python code to be executed into the
-     ``debugger_script`` field in ``_PyRemoteDebuggerSupport``.
+   - Most debuggers will pause the process before writing to its memory. This is 
+     standard practice for tools like GDB, which use SIGSTOP or ptrace to pause the process.
+     This approach prevents races when writing to process memory. Profilers and other tools 
+     that don't wish to stop the process can still use this interface, but they need to 
+     handle possible races, which is a normal consideration for profilers in general.
+
+   - Write a file path to a Python source file (.py) into the
+     ``debugger_script_path`` field in ``_PyRemoteDebuggerSupport``.
    - Set ``debugger_pending_call`` flag in ``_PyRemoteDebuggerSupport``
    - Set ``_PY_EVAL_PLEASE_STOP_BIT`` in the ``eval_breaker`` field
 
-Once the interpreter reaches the next safe point, it will execute the script
-provided by the debugger.
+Once the interpreter reaches the next safe point, it will execute the Python code 
+contained in the file specified by the debugger.
 
 Interpreter Integration
 -----------------------
@@ -233,7 +240,7 @@ to be audited or disabled if desired by a system's administrator.
     if (tstate->eval_breaker) {
         if (tstate->remote_debugger_support.debugger_pending_call) {
             tstate->remote_debugger_support.debugger_pending_call = 0;
-            const char *path = tstate->remote_debugger_support.debugger_script;
+            const char *path = tstate->remote_debugger_support.debugger_script_path;
             if (*path) {
                 if (0 != PySys_Audit("debugger_script", "%s", path)) {
                     PyErr_Clear();
@@ -269,16 +276,17 @@ arbitrary Python code within the context of a specified Python process:
 
 .. code-block:: python
 
-  def remote_exec(pid: int, code: str, timeout: int = 0) -> None:
+  def remote_exec(pid: int, code: str) -> None:
       """
       Executes a block of Python code in a given remote Python process.
 
+      This function returns immediately, and the code will be executed at the next
+      available opportunity in the target process, similar to how signals are handled.
+      There is no way to determine when or if the code has been executed.
+
       Args:
            pid (int): The process ID of the target Python process.
            code (str): A string containing the Python code to be executed.
-           timeout (int): An optional timeout for waiting for the remote
-              process to execute the code. If the timeout is exceeded a
-              ``TimeoutError`` will be raised.
       """
 
 An example usage of the API would look like:
@@ -288,9 +296,7 @@ An example usage of the API would look like:
     import sys
     # Execute a print statement in a remote Python process with PID 12345
     try:
-        sys.remote_exec(12345, "print('Hello from remote execution!')", timeout=3)
-    except TimeoutError:
-        print(f"The remote process took too long to execute the code")
+        sys.remote_exec(12345, "print('Hello from remote execution!')")
     except Exception as e:
         print(f"Failed to execute code: {e}")
 
@@ -393,8 +399,8 @@ Rejected Ideas
 Writing Python code into the buffer
 -----------------------------------
 
-We have chosen to have debuggers write the code to be executed into a file
-whose path is written into a buffer in the remote process. This has been deemed
+We have chosen to have debuggers write the path to a file containing Python code
+into a buffer in the remote process. This has been deemed
 more secure than writing the Python code to be executed itself into a buffer in
 the remote process, because it means that an attacker who has gained arbitrary
 writes in a process but not arbitrary code execution or file system