New submission from Jeremy <[email protected]>:
If a unittest is written which accesses a module written in C++ (I used
Pybind11 to allow Python access) which uses malloc for a string, a segmentation
fault is caused. This is not replicated when malloc is used for some other data
types such as int, char or char*
C++ code:
#include <string>
#include <pybind11/pybind11.h>
#include <pybind11/stl.h>
using namespace std;
void t(){
string * data = (string*)malloc(100*sizeof(string));
data[0] = "this is a test";
cout<<data[0]<<endl;
}
PYBIND11_MODULE(TestModule, m){
m.def("editPointerString", &t);
}
Once compiled and imported this can be run fine with editPointerString() as
expected. No errors occur when running this function from any Python functions
or from within a class.
However, if this is run through a unittest such as:
class TestUnit(unittest.TestCase):
def testStringPointer(self):
editPointerString()
A segmentation fault occurs before the cout<<data[0]<<endl; is executed. Not
having an assert statement does not affect this outcome.
However, running 3 or more tests which call this function allows the tests to
run and pass - instead displaying there has been a segmentation fault after the
OK message from unittest
This can be fixed by using calloc instead of malloc, so may be caused by
processing of data which is not cleared when malloc is used?
Also, malloc can be used in functions in tests after a test running calloc has
been run.
System info:
Python 3.7.3
Ubuntu 19.04
pybind11 2.3.0
g++ 8.3.0
C++ 8.3.0
----------
components: Extension Modules, Library (Lib)
messages: 351243
nosy: ymerej
priority: normal
severity: normal
status: open
title: unittest causing segfaults with string malloc in c++ module
type: crash
versions: Python 3.7
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Python tracker <[email protected]>
<https://bugs.python.org/issue38044>
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