Mailman 3 August 2012 - Cplusplus-sig

boost::python embedding error - runtime - Mac OS X - 1.38
by Igor Karpov Oct. 1, 2014

Oct. 1, 2014

Hi, I am trying to run the following program: #include <iostream> #include <Python.h> #include <boost/python.hpp> using namespace boost::python; using namespace std; int main(int argc, char** argv) { { // Using Python/C Py_Initialize(); PyObject* main_module = PyImport_ImportModule("__main__"); PyObject* globals = PyEval_GetGlobals(); PyObject* locals = PyEval_GetLocals(); PyRun_SimpleString("print 'Hello World, from Python/C!'\n"); Py_Finalize(); } { // Using boost::python Py_Initialize(); object main_module = import("__main__"); object main_namespace = main_module.attr("__dict__"); try { object ignored = exec("print 'Hello World, from boost::python!'\n", main_namespace); Py_Finalize(); } catch (error_already_set const& e) { PyErr_Print(); return 1; } } return 0; } on Linux (both x86 and x86_64), with Ubuntu's default version of Boost (1.34.1) installed, I am able to do so as expected: $ ./embed Hello World, from Python/C! Hello World, from boost::python! on Mac OS X, I get a runtime error: $ ./embed Hello World, from Python/C! Bus Error Running with gdb, this is the stack trace: Hello World, from Python/C! Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_PROTECTION_FAILURE at address: 0x00000000 0x00000000 in ?? () (gdb) where #0 0x00000000 in ?? () #1 0x00bb618f in PyEval_GetGlobals () #2 0x00bce0dd in PyImport_Import () #3 0x00bce2b0 in PyImport_ImportModule () #4 0x008127d4 in boost::python::import (name=@0xbffff4a8) at libs/python/src/import.cpp:20 #5 0x00004446 in main (argc=1, argv=0xbffff510) at embed.cc:22 For this Mac, boost version is latest (1.38) and python version is: Python 2.5.4 (r254:67917, Dec 23 2008, 14:57:27) [GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin Is this a bug? I attached the source and the cmake file I am using to build, for convenience. Thanks, --Igor.

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sendkeys method
by sam Sept. 30, 2013

Sept. 30, 2013

Hello, Is there away(method) in C/C++ programming that make the software think that someone pressed the OK button, similar to sendkeys in VBS (WshShell.SendKeys ("{Enter}")) Thank you, Sam

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building 32 Bit and 64 Bit extensions on the same machine
by Ronny Herzog Sept. 5, 2012

Sept. 5, 2012

Dear all, I want to build 32 bit extensions and 64 bit extensions on my Windows 7 / 32 Bit with boost. After two days of checking google I am a bit frustrated. I am new to Boost and it is a bit like a jungle. Can anyone help on what I need to do to set up Boost in the right way and have a Jamroot which allows me to compile my Python extensions in 32 Bit and 64 Bit at the same time (with MSVC 2008). Thanks a lot, Ronny

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boost-python: Passing an object held in a boost::shared_ptr from C++ to python to C++
by Philip Dunstan Aug. 31, 2012

Aug. 31, 2012

Hi I have some code that creates an object in a shared_ptr in C++. The object is then used within python and passed from Python to another C++ function that tries to keep hold of it. It appears that when the object goes from C++ to Python it is converted from a shared_ptr<X> into a python object. Then when it goes back into C++ it is converted from the python object into a new shared_ptr<X>, however this shared_ptr is unrelated to the initial holding shared_ptr. Is it possible to set up the boost-python bindings so that the conversion from python object to shared_ptr references the original shared_ptr internals? Below is the abridged code I have used to show the problem. I have attached the full reproducible to this email. In this example an object is initially held in a shared_ptr named s_iniital. It is grabbed from within python through the getSharedPtr function, then pushed back into C++ through the putSharedPtr function. Inside putSharedPtr it is copied into the weak_ptr s_copied. Inspecting the pointers in the debugger shows that the shared_ptr used in putSharedPtr does not have the same reference counting internals as s_initial. The final assert will fire because the weak pointer s_copied was only related to a single strong pointer (the pointer used in putSharedPtr) and that pointer was destructed once putSharedPtr was finished. static shared_ptr<Captured> s_initial; static weak_ptr<Captured> s_copied; class UseSharedPtr { public: shared_ptr<Captured> getSharedPtr() { return s_initial; } void putSharedPtr(shared_ptr<Captured> ptr) { s_copied = ptr; } }; BOOST_PYTHON_MODULE(test) { class_<Captured, shared_ptr<Captured>, boost::noncopyable>("Captured", no_init); class_<UseSharedPtr, boost::noncopyable>("UseSharedPtr", init<>()) .def("getSharedPtr", &UseSharedPtr::getSharedPtr) .def("putSharedPtr", &UseSharedPtr::putSharedPtr) ; } s_initial = make_shared<Captured>(); const char* chunk = "\ from test import UseSharedPtr \n\ x = UseSharedPtr() \n\ ptr = x.getSharedPtr() \n\ x.putSharedPtr(ptr)\n\ del x \n\ del ptr \n\ "; object result = exec(chunk, mainNamespace, mainNamespace); assert(s_copied.lock()); thanks, Phil -- Philip Dunstan phil(a)philipdunstan.com www.philipdunstan.com

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`cout << tuple` is ambiguous
by Holger Brandsmeier Aug. 26, 2012

Aug. 26, 2012

Dear list, I get the following error error: use of overloaded operator '<<' is ambiguous (with operand types 'basic_ostream<char, std::char_traits<char> >' and 'const boost::python::tuple') The two candidates are an output operator for tuple, which I want to use /usr/include/boost-1_48/boost/python/object_operators.hpp:105:1: note: candidate function [with L = std::basic_ostream<char>, R = boost::python::tuple] BOOST_PYTHON_BINARY_OPERATOR(<<) /usr/include/boost-1_48/boost/python/object_operators.hpp:90:36: note: expanded from macro 'BOOST_PYTHON_BINARY_OPERATOR' BOOST_PYTHON_BINARY_RETURN(object) operator op(L const& l, R const& r) \ And an output operator for bools /usr/lib/gcc/x86_64-pc-linux-gnu/4.5.3/include/g++-v4/ostream:172:7: note: candidate function operator<<(bool __n) How do I avoid this ambiguity with booleans? And how can I output tuples? Btw. the compiler that I used is `clang version 3.1 (trunk 154212)` Best regards, Holger Brandsmeier

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Boost::Python and Functions with String Inputs
by Hesam Aug. 26, 2012

Aug. 26, 2012

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Re: [C++-sig] building 32 Bit and 64 Bit extensions on the same machine
by Wojciech Mamrak Aug. 26, 2012

Aug. 26, 2012

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Boost::Python and Functions with String Inputs
by Hesam Aug. 24, 2012

Aug. 24, 2012

*Dear Sirs,* *Goal:* I'm trying to use python interactively in my c++ code using Boost::Python library. My goal is to change variables of some class which I have defined in c++ from the python interpreter. The code is attached below. Actually this comes from Boost::Python tutorials http://www.boost.org/doc/libs/1_51_0/libs/python/doc/tutorial/doc/html/pyth… *Problem:* I can load the library in python interface (i.e. load hello) and make an object out of it (obj = hello.World()). I even can access functions ( obj.greet() ) but when I want to access functions with string input (obj.set("Hello") ) I get memory access violation ("Access violation reading location 0xffffffffffffffff"). *The problem is just with string inputs. i.e. if I change function set(string) to set(char*) it works fine. * If instead of interpreter I use PyRun_SimpleString("import hello; w=hello.World(); w.set('Hi there');\n"); I get error "Expression _BLOCK_TYPE_IS_VALID(pHead->nBlockUse)". The point is when I make breakpoint inside the function value of string is not what I want. *Details*: Visual studio 2010 (MDd mode), Debug Mode, x64, Win7 struct World { void set(string _msg) {} string greet() { return msg; } string msg; }; typedef boost::shared_ptr<World> World_ptr; BOOST_PYTHON_MODULE(hello) { bp::class_<World, World_ptr>("World") .def("greet", &World::greet) .def("set", &World::set) ; } int main(int argc, char **argv) { Py_Initialize(); bp::object main = bp::object(bp::handle<>(bp::borrowed(PyImport_AddModule("__main__")))); bp::object global(main.attr("__dict__")); inithello(); // Bring up Python interpreter Py_Main(argc, argv); Py_Finalize(); return 0; } Actually this comes from Boost::Python tutorials with some modification to use Python interpreter http://www.boost.org/doc/libs/1_51_0/libs/python/doc/tutorial/doc/html/pyth… Many thanks [image: Inline image 1]

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issues with loading the boost_python dll on different computers
by Ronny Herzog Aug. 24, 2012

Aug. 24, 2012

Dear all, I installed and used boost (1.50.0) to build a python extension on my Windows 7 / 32 Bit. Everything worked fine. Now I tried the extension module on other Computers with Windows 7 and Windows XP and the same Python version and it gave me an error concerning the DLL: ** ImportError : DLL load failed: This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem. ** Would anyone have a hint on were this problem could come from. I am totally clueless. Thanks a lot, Ronny

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Accessing 2D array from python in C++
by shahmi Aug. 22, 2012

Aug. 22, 2012

Hi, I have tried to access/expose 2D array from python in C++ using boost::multi_array. Nevertheless, it seems that the boost::multi_array<double, 2> datatype is not supported. Is there any way to resolve this? My way of accessing it as below: boost::python::object Vp = main_namespace["Vp"]; Vp_cpp = boost::python::extract<boost::multi_array<double, 2> >(Vp); I've also tried to try to use 2D vector as below, nonetheless, it still doesn't work: boost::python::object Vp = main_namespace["Vp"]; Vp_cpp = boost::python::extract<std::vector<std::vector<double> > >(Vp); The error message I received is "TypeError: No registered converter was able to produce a C++ rvalue of type std::vector<std::vector<double, std::allocator<double> >, std::allocator<std::vector<double, std::allocator<double> > > > from this Python object of type matrix" Thanks in advance.

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