Move get_signal_name() to test.support (#121251)

* Move get_signal_name() from test.libregrtest to test.support.
* Use get_signal_name() in support.script_helper.
* support.script_helper now decodes stdout and stderr from UTF-8,
  instead of ASCII, if a command failed.

2 files changed, 51 insertions, 17 deletions

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index dbea070..18455bb 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2632,3 +2632,35 @@ def initialized_with_pyrepl():
     """Detect whether PyREPL was used during Python initialization."""
     # If the main module has a __file__ attribute it's a Python module, which means PyREPL.
     return hasattr(sys.modules["__main__"], "__file__")
+
+
+WINDOWS_STATUS = {
+    0xC0000005: "STATUS_ACCESS_VIOLATION",
+    0xC00000FD: "STATUS_STACK_OVERFLOW",
+    0xC000013A: "STATUS_CONTROL_C_EXIT",
+}
+
+def get_signal_name(exitcode):
+    import signal
+
+    if exitcode < 0:
+        signum = -exitcode
+        try:
+            return signal.Signals(signum).name
+        except ValueError:
+            pass
+
+    # Shell exit code (ex: WASI build)
+    if 128 < exitcode < 256:
+        signum = exitcode - 128
+        try:
+            return signal.Signals(signum).name
+        except ValueError:
+            pass
+
+    try:
+        return WINDOWS_STATUS[exitcode]
+    except KeyError:
+        pass
+
+    return None
diff --git a/Lib/test/support/script_helper.py b/Lib/test/support/script_helper.py
index 65e0bc1..d0be317 100644
--- a/Lib/test/support/script_helper.py
+++ b/Lib/test/support/script_helper.py
@@ -70,23 +70,25 @@ class _PythonRunResult(collections.namedtuple("_PythonRunResult",
             out = b'(... truncated stdout ...)' + out[-maxlen:]
         if len(err) > maxlen:
             err = b'(... truncated stderr ...)' + err[-maxlen:]
-        out = out.decode('ascii', 'replace').rstrip()
-        err = err.decode('ascii', 'replace').rstrip()
-        raise AssertionError("Process return code is %d\n"
-                             "command line: %r\n"
-                             "\n"
-                             "stdout:\n"
-                             "---\n"
-                             "%s\n"
-                             "---\n"
-                             "\n"
-                             "stderr:\n"
-                             "---\n"
-                             "%s\n"
-                             "---"
-                             % (self.rc, cmd_line,
-                                out,
-                                err))
+        out = out.decode('utf8', 'replace').rstrip()
+        err = err.decode('utf8', 'replace').rstrip()
+
+        exitcode = self.rc
+        signame = support.get_signal_name(exitcode)
+        if signame:
+            exitcode = f"{exitcode} ({signame})"
+        raise AssertionError(f"Process return code is {exitcode}\n"
+                             f"command line: {cmd_line!r}\n"
+                             f"\n"
+                             f"stdout:\n"
+                             f"---\n"
+                             f"{out}\n"
+                             f"---\n"
+                             f"\n"
+                             f"stderr:\n"
+                             f"---\n"
+                             f"{err}\n"
+                             f"---")
 
 
 # Executing the interpreter in a subprocess