Write one error message directly to stderr instead of sys.stderr. This

lets us avoid taking the GIL, which might crash in case the Python
interpreter is not initialized at all.

3 files changed, 44 insertions, 37 deletions

diff --git a/testing/cffi0/test_function.py b/testing/cffi0/test_function.py
index b4c98e7..8fdcc86 100644
--- a/testing/cffi0/test_function.py
+++ b/testing/cffi0/test_function.py
@@ -4,6 +4,7 @@ import math, os, sys
 import ctypes.util
 from cffi.backend_ctypes import CTypesBackend
 from testing.udir import udir
+from testing.support import FdWriteCapture
 
 try:
     from StringIO import StringIO
@@ -11,29 +12,6 @@ except ImportError:
     from io import StringIO
 
 
-class FdWriteCapture(object):
-    """xxx limited to capture at most 512 bytes of output, according
-    to the Posix manual."""
-
-    def __init__(self, capture_fd):
-        self.capture_fd = capture_fd
-
-    def __enter__(self):
-        self.read_fd, self.write_fd = os.pipe()
-        self.copy_fd = os.dup(self.capture_fd)
-        os.dup2(self.write_fd, self.capture_fd)
-        return self
-
-    def __exit__(self, *args):
-        os.dup2(self.copy_fd, self.capture_fd)
-        os.close(self.copy_fd)
-        os.close(self.write_fd)
-        self._value = os.read(self.read_fd, 512)
-        os.close(self.read_fd)
-
-    def getvalue(self):
-        return self._value
-
 lib_m = 'm'
 if sys.platform == 'win32':
     #there is a small chance this fails on Mingw via environ $CC
@@ -135,7 +113,7 @@ class TestFunction(object):
         """)
         ffi.C = ffi.dlopen(None)
         ffi.C.fputs   # fetch before capturing, for easier debugging
-        with FdWriteCapture(2) as fd:
+        with FdWriteCapture() as fd:
             ffi.C.fputs(b"hello\n", ffi.C.stderr)
             ffi.C.fputs(b"  world\n", ffi.C.stderr)
         res = fd.getvalue()
@@ -151,7 +129,7 @@ class TestFunction(object):
         """)
         ffi.C = ffi.dlopen(None)
         ffi.C.fputs   # fetch before capturing, for easier debugging
-        with FdWriteCapture(2) as fd:
+        with FdWriteCapture() as fd:
             ffi.C.fputs(b"hello\n", ffi.C.stderr)
             ffi.C.fputs(b"  world\n", ffi.C.stderr)
         res = fd.getvalue()
@@ -166,7 +144,7 @@ class TestFunction(object):
            void *stderr;
         """)
         ffi.C = ffi.dlopen(None)
-        with FdWriteCapture(2) as fd:
+        with FdWriteCapture() as fd:
             ffi.C.fprintf(ffi.C.stderr, b"hello with no arguments\n")
             ffi.C.fprintf(ffi.C.stderr,
                           b"hello, %s!\n", ffi.new("char[]", b"world"))
@@ -228,7 +206,7 @@ class TestFunction(object):
         fptr = ffi.cast("int(*)(const char *txt, void *)", ffi.C.fputs)
         assert fptr == ffi.C.fputs
         assert repr(fptr).startswith("<cdata 'int(*)(char *, void *)' 0x")
-        with FdWriteCapture(2) as fd:
+        with FdWriteCapture() as fd:
             fptr(b"world\n", ffi.C.stderr)
         res = fd.getvalue()
         assert res == b'world\n'
diff --git a/testing/cffi1/test_recompiler.py b/testing/cffi1/test_recompiler.py
index ee77c5c..81c43ef 100644
--- a/testing/cffi1/test_recompiler.py
+++ b/testing/cffi1/test_recompiler.py
@@ -4,7 +4,7 @@ from cffi import FFI, VerificationError, FFIError
 from cffi import recompiler
 from testing.udir import udir
 from testing.support import u
-from StringIO import StringIO
+from testing.support import FdWriteCapture, StdErrCapture
 
 
 def check_type_table(input, expected_output, included=None):
@@ -1486,14 +1486,6 @@ def test_win32_calling_convention_3():
     pt = ptr_call2(ffi.addressof(lib, 'cb2'))
     assert (pt.x, pt.y) == (99*500*999, -99*500*999)
 
-class StdErrCapture(object):
-    def __enter__(self):
-        self.old_stderr = sys.stderr
-        sys.stderr = f = StringIO()
-        return f
-    def __exit__(self, *args):
-        sys.stderr = self.old_stderr
-
 def test_extern_python_1():
     ffi = FFI()
     ffi.cdef("""
@@ -1506,7 +1498,7 @@ def test_extern_python_1():
     """)
     lib = verify(ffi, 'test_extern_python_1', "")
     assert ffi.typeof(lib.bar) == ffi.typeof("int(*)(int, int)")
-    with StdErrCapture() as f:
+    with FdWriteCapture() as f:
         res = lib.bar(4, 5)
     assert res == 0
     assert f.getvalue() == (
diff --git a/testing/support.py b/testing/support.py
index 17c56cd..17ee621 100644
--- a/testing/support.py
+++ b/testing/support.py
@@ -17,3 +17,40 @@ else:
     u = ""
     unicode = str
     long = int
+
+
+class StdErrCapture(object):
+    """Capture writes to sys.stderr (not to the underlying file descriptor)."""
+    def __enter__(self):
+        import StringIO
+        self.old_stderr = sys.stderr
+        sys.stderr = f = StringIO.StringIO()
+        return f
+    def __exit__(self, *args):
+        sys.stderr = self.old_stderr
+
+
+class FdWriteCapture(object):
+    """xxx limited to capture at most 512 bytes of output, according
+    to the Posix manual."""
+
+    def __init__(self, capture_fd=2):    # stderr by default
+        self.capture_fd = capture_fd
+
+    def __enter__(self):
+        import os
+        self.read_fd, self.write_fd = os.pipe()
+        self.copy_fd = os.dup(self.capture_fd)
+        os.dup2(self.write_fd, self.capture_fd)
+        return self
+
+    def __exit__(self, *args):
+        import os
+        os.dup2(self.copy_fd, self.capture_fd)
+        os.close(self.copy_fd)
+        os.close(self.write_fd)
+        self._value = os.read(self.read_fd, 512)
+        os.close(self.read_fd)
+
+    def getvalue(self):
+        return self._value