Fix a signedness compiler warning in vector.to_py #5438
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When compiling cythonized code which uses `std::vector` we get the
following compiler warning on GCC 8 and Python 3.9 (which is turned into
an error in our case):
```
my_file.cpp: In function ‘PyObject* __pyx_convert_vector_to_py_int(const std::vector<int>&)’:
my_file.cpp:4716:33: warning: comparison of integer expressions of different signedness: ‘Py_ssize_t’ {aka ‘long int’} and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
for (__pyx_t_5 = 0; __pyx_t_5 < __pyx_t_4; __pyx_t_5+=1) {
~~~~~~~~~~^~~~~~~~~~~
```
The generated code in question is as follows:
```
/* "vector.to_py":75
* cdef object item
*
* for i in range(v.size()): # <<<<<<<<<<<<<<
* item = v[i]
* Py_INCREF(item)
*/
__pyx_t_3 = __pyx_v_v.size();
__pyx_t_4 = __pyx_t_3;
for (__pyx_t_5 = 0; __pyx_t_5 < __pyx_t_4; __pyx_t_5+=1) {
__pyx_v_i = __pyx_t_5;
```
`__pyx_t_5` is of type `‘Py_ssize_t’` (signed), and `__pyx_t_4` aka
`__pyx_t_3` is `size_t` (unsigned), causing GCC to rightfully complain.
Fix the generated code by explicitly using the signed variant of the
vector's size in the loop.
This bug has been introduced in
cython#4081, which also contains some
discussion on the use of signed vs unsigned types. This patch chooses to
keep the status quo and only fixes the compiler warning.
|
Thanks, that looks god. |
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When compiling cythonized code which uses
std::vectorwe get the following compiler warning on GCC 8 and Python 3.9 (which is turned into an error in our case):The generated code in question is as follows:
__pyx_t_5is of type‘Py_ssize_t’(signed), and__pyx_t_4aka__pyx_t_3issize_t(unsigned), causing GCC to rightfully complain.Fix the generated code by explicitly using the signed variant of the vector's size in the loop.
This bug has been introduced in
#4081, which also contains some discussion on the use of signed vs unsigned types. This patch chooses to keep the status quo and only fixes the compiler warning.