gencffi: Detect functions returning a Go error #105
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corona10
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_examples/pyerrors/pyerrors.go
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| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
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| // pyerrors is a package to test detecting errors. |
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s/pyerrors is a package to test detecting errors/Package pyerrors holds functions returning an error/
_examples/pyerrors/test.py
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| r = pyerrors.Div(a, b) | ||
| print("pyerrors.Div(%d, %d) = %d"% (a, b, r)) | ||
| except RuntimeError: | ||
| print("Error detected.") |
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it would also be interesting to print the error we caught, as well as for which input arguments it failed.
you should also probably add an except Exception case as a catch all.
| case 1: | ||
| g.wrapper.Printf("if not _cffi_helper.lib._cgopy_ErrorIsNil(cret):\n") | ||
| g.wrapper.Indent() | ||
| g.wrapper.Printf("c_err_str = _cffi_helper.lib._cgopy_ErrorString(cret)\n") |
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I haven't checked, but, do you know what's the memory ownership model for C-strings being passed by _cgopy_ErrorString ?
and what is its interaction with ffi.string ?
ie: who's supposed to free the C-string ?
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@sbinet
For about ffi.string. I am using this because of Py3 string handling.
(Next PR would be about handling python3 string.)
It's kind of utility function, which copies the string value from string pointer and join into python string. (Internally, it uses ctypes.)
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@sbinet
Here is the reference from CFFI documentation.
Any operation that would in C return a pointer or array or struct type gives you a fresh cdata >object. Unlike the “original” one, these fresh cdata objects don’t have ownership: they are merely references to existing memory.
* Detect functions returning a Go error and make them pythonic (raising an Exception). * Add tests for it. Now it only supports 2 return values. CPy2 and CFFI should support more return values. Fixes: go-python#104
| @@ -89,6 +89,11 @@ func _cgopy_ErrorString(err error) *C.char { | |||
| return C.CString(err.Error()) | |||
| } | |||
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| //export _cgopy_FreeCString | |||
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@sbinet
I add this function to free the C-string manually.
Now it only supports 2 return values.
CPy2 and CFFI should support more return values.
Fixes: #104