I'm attempting to make a GUI package manager for Ubuntu similar to Synaptic which uses libapt but have run into a few strange bugs to do with getting information from the pkgCache. Specifically when using a pkgIterator and trying to access the FullName() and Name() properties but others like Section() are fine (you can look at documentation here).
Looking at the way Synaptic does it, it is pretty simple and I tried replicating it 1:1 with no luck.
const char *name() {
const char *n = package->Name();
if (n == NULL)
return "";
return n;
}
Which will usually return some garbage string that looks like a null termination was missed. The interesting thing is that all of the strings for packages in the same group from repositories will have the same garbage text while locally installed packages will have a NULL pointer and therefore will return an empty string.
Any ideas? I believe that I'm opening the pkgCache correctly and the iterator is not NULL. Theres also not many places to look online when debugging libapt so any references would be helpful as well!.
Related
I implemented Aspose.Cells and Aspose.PDF into our companies existing application.
While I had some trouble with this (mostly caused by the fact that I tried to implement both APIs into the exat same file which was a bad idea)
I figured out how to make it work more or less.
My Problem now is while Aspose.Cells works perfectly fine and doesn't seem to have any unusual behavior Aspose.PDF already struggles with setting the license and even when I eventually got this to work I can't even initiate a Aspose::Pdf::Document.
So the first totally unusual thing is the way I had to set the License in the Example code given with the Aspose Package and in the official resources the license is set like this.
auto lic = System::MakeObject<Aspose::Pdf::License>();
lic->SetlLicense("c:\\Foo\fooproj\\Aspose.Total.C++.lic");
This code won't run on my machine and cause the error.
Rough Translation
food.exe triggered a breakpoint
Original
food.exe Hat einen Haltepunkt ausgelöst
The same happens when I initialise a System::String with a emtpy constructor like this.
auto lic = System::MakeObject<Aspose::Pdf::License>();
System::String str;
str.FromUtf8("C:\\foo\fooproj\\Aspose.Total.C++.lic");
lic->SetLicense(str);
BUT if I initialise the System::String with an empty String in the first place setting the license seems to work just fine so this works.
auto lic = System::MakeObject<Aspose::Pdf::License>();
System::String str(u"");
str.FromUtf8("C:\\Projekte\\Aspose\\Lizens\\Aspose.Total.C++.lic");
lic->SetLicense(str);
If this code above works and I try to make an object from Aspose::Pdf::Document this will crash.
void Aspose_pdf::helloWorld()
{
auto doc = System::MakeObject<Aspose::Pdf::Document>();
.....
.....
}
I actually have no idea what's going on. I am not using any using namespace commands at the moment.
Would be greate if someone had an idea how to fix this.
Edit:
The error occures exactly in smart_ptr.h in the following function.
typename std::enable_if<!IsSmartPtr<T>::value, SmartPtr<T> >::type MakeObject(Args&&... args)
{
System::Detail::OwnNextObject ownershipSentry;
T *const object = ::new T(std::forward<Args>(args)...);
ownershipSentry.CreatedSuccessfully(object);
return SmartPtr<T>(object);
}
in the second line so T *const object = ::new T(std::forward<Args>(args)...);
is "causing" the error or atleast here the error will ne triggered.
Edit2:
Here you will find a simple example of how my code looks in general.
I Started with implementing Aspose.Pdf into my Programm so I edited my
Additional Library directories,additional dependencies, additional include directories,preprozessor definitions and my stacksize to fit these settings given in the Aspose.Pdf examples.
After this I created my Aspose_Pdf class and tested it. worked perferctly so far.
After this I made the same edits to fit Aspose.Cells aswell. Also I created a class Aspose_Cells and tested it. While this worked now my Aspose_Pdf class stoped working. After a little time passed I managed to atleast get the License Activation for Aspose_Pdf to work from this point on I had the problems described above.
Additional Dependencies:
...
Aspose.PDF_vc141x64d.lib
aspose_cpp_vc141x64d.lib
Aspose.Cells.lib
Additional Librariedirectories:
...
..\Aspose\Aspose.PDF\lib\Debug
..\Aspose\Aspose.Cells\lib64
additional Includedirectories
...
..\Aspose\Aspose.PDF\lib\Debug
..\Aspose\Aspose.PDF\include\asposecpplib
..\Aspose\Aspose.PDF\include\Aspose.Pdf.Cpp
..\Aspose\Aspose.Cells\Include
..\Aspose\Aspose.Cells\Include\icu\include
..\Aspose\Aspose.Cells\Include\boost
I've never heard about Aspose.Pdf neither I know how does System::MakeObject< work. But for me it looks that all the code might be simplified to next:
Aspose::Pdf::License^ lic = gcnew Aspose::Pdf::License();
System::String^ str = "C:\\foo\\fooproj\\Aspose.Total.C++.lic";
lic->SetLicense(str);
When it comes to Pdf.Document the initialization might look like this:
Aspose::Pdf::Document^ doc = gcnew Aspose::Pdf::Document();
I have a program that uses plug-ins. As I'm in development, these plug-ins are currently just .h and .cpp files that I add or remove from my project before re-compiling, but eventually they will be libraries.
Each plug-in contains lists of data in vectors, and I need to dynamically load data from the plug-ins without knowing which plug-ins are present. For instance:
// plugin1.h
extern vector<int> plugin1Data;
// plugin2.h
extern vector<int> plugin2Data;
// main.cpp
vector<vector<int>> pluginDataList;
int CountPlugins () {
// Some function that counts how many plug-ins are present, got this bit covered ;)
}
int main() {
int numPlugins = CountPlugins();
for (int i = 0; i < numPlugins; i++) {
vector<int> newPluginData = /***WAY TO ADD PLUGIN DATA!!!***/;
pluginDataList.push_back(newPluginData);
}
}
I already access the names of each plugin present during my CountPlugins() function, and have a list of names, so my first gut feeling was to use the name from each plugin to create a variable name like:
vector<string> pluginNames = /*filled by CountPlugins*/;
string pluginDataName = pluginNames.at(i) + "Data";
// Use pluginDataName to locate plugin1Data or plugin2Data
That's something I've done before in c# when I used to mess around with unity, but I've read a few stackoverflow posts clearly stating that it's not possible in c++. It's also a fairly messy solution in C# anyway as far as I remember.
If each plugin was a class instead of just a group of vectors, I could access the specific data doing something like plugin2.data... but then I still need to be able to reference the object stored within each plugin, and that'll mean that when I get round to compiling the plugins as libraries, I'll always have to link to class declaration and definition, which isn't ideal (though not out of the question if it'll give a nicer solution over all).
I'm all out of ideas after that, any help you can offer will be most welcome!
Thanks! Pete
Why dont you save the data as JSON between the application and the plugins ? That way you will also allow other types of tech to plug-into your app, like javascript based plugins via an embedded version of v8 or c#/.net plugins via mono.'
I want to write checker that can be added to other checkers in CppCheck. This checker must check SLOC of all member function, for example the function should contain no more than 200 significant lines of code. But in CppCheck I only found method that checks the existence of a body hasBody(), but not a count of lines.
I am a cppcheck developer. I am no expert in this topic. I think it depends on exactly what you want to count. how many lines is this:
void f() { int x=3; int y=x+2; dostuff(x+y+4); }
I would guess that you want to go through the tokens and count semicolons or something:
for (tok = functionScope->classStart; tok != functionScope->classEnd; tok = tok->next()) {
if (tok->str() == ";")
++lines;
}
I think this checker you suggest is interesting but it does not fit well in the core cppcheck tool. I would suggest that you write an addon. I will be happy to add it in our addons folder and show it in the GUI etc.
By the way.. I have thought that it would be nice to integrate (execute and read results) ohcount, cccc, or whatever in the GUI so extended statistics can be shown.
I'm not sure if this will be a specific thing with jsoncpp or a general paradigm with how to make a C++ library behave better. Basically I'm getting this trace:
imagegeneratormanager.tsk: src/lib_json/json_value.cpp:1176: const Json::Value& Json::Value::operator[](const char*) const: Assertion `type_ == nullValue || type_ == objectValue' failed.
That happens when the input is bad. When the input - which is coming from another application of mine via memcached - happens to be bad, I would like to handle this error. You know, gracefully. Perhaps something like, "error: input for item 15006 is bad" going to the log. Not crashing my entire JSON-string-processing task.
Is this just a badly written library or is it possible to configure it more subtly?
Edit: here's some calling code:
Json::Value root;
Json::Reader reader;
succeeded = reader.parse(jsonString, root);
if(!succeeded) {
throw std::runtime_error(std::string("Failed to parse JSON for key ") + emailInfoKey.str());
}
std::string userEmail = root.get("userId", "").asString();
std::string bodyFilePath = root.get("bodyFilePath", "").asString();
std::string msgId = root.get("msgId", "").asString();
According to the library reference:
Value & Json::Value::operator[] ( const StaticString & key )
Access an object value by name, create a null member if it does not exist.
Seems you are trying to call operator[] on a non-object, say an integer or a string (get internally uses operator[]). You are breaking the function precondition, and its an error on your side of the code, not the library. You could check if the Json::Value is an object before accessing it as such using isObject().
As I see from the JsonCpp Sourceforge repo, right now assertions aren't catchable (however it seems to be in their backlog to make throwing assertions).
Then, you'll have to test if the input is valid before calling the [] operator.
A link to the source code of the newest revision (I don't know the version you have). See line 1141:
http://jsoncpp.svn.sourceforge.net/viewvc/jsoncpp/trunk/jsoncpp/src/lib_json/json_value.cpp?revision=249&view=markup
In the simplest possible terms (I'm an occasional programmer who lacks up-to-date detailed programming knowledge) can someone explain the simplest way to make use of the registry in codegear C++ (2007).
I have a line of code in an old (OLD!) program I wrote which is causing a significant delay in startup...
DLB->Directory=pIniFile->ReadString("Options","Last Directory","no key!");
The code is making use of an ini file. I would like to be able to use the registry instead (to write variables such as the last directory the application was using)
But the specifics are not important. I'd just like a generic how-to about using the registry that's specific to codegear c++ builder.
I've googled this, but as usual with this type of thing I get lots of pages about c++ builder and a few pages about the windows registry, but no pages that explain how to use one with the other.
Use the TRegistry class... (include registry.hpp)
//Untested, but something like...
TRegistry *reg = new TRegistry;
reg->RootKey = HKEY_CURRENT_USER; // Or whatever root you want to use
reg->OpenKey("theKey",true);
reg->ReadString("theParam",defaultValue);
reg->CloseKey();
Note, opening and reading a ini file is usually pretty fast, so maybe you need to test your assumption that the reading of the ini is actually your problem, I don't think that just grabbing your directory name from the registry instead is going to fix your problem.
Include the Registry.hpp file:
#include <Registry.hpp>
Then in any function you have, you can write the following to read the value:
String __fastcall ReadRegistryString(const String &key, const String &name,
const String &def)
{
TRegistry *reg = new TRegistry();
String result;
try {
reg->RootKey = HKEY_CURRENT_USER;
if (reg->OpenKeyReadOnly(key)) {
result = reg->ReadString(name, def);
reg->CloseKey();
}
}
__finally {
delete reg;
}
return result;
}
So reading the value should be as easy as:
ShowMessage(ReadRegistryString("Options", "Last Directory", "none"));
You can use the following to write the value:
void __fastcall WriteRegistryString(const String &key, const String &name,
const String &value)
{
TRegistry *reg = new TRegistry();
try {
reg->RootKey = HKEY_CURRENT_USER;
if (reg->OpenKey(key, true)) {
reg->WriteString(name, value);
reg->CloseKey();
}
}
__finally {
delete reg;
}
}
Should be self explaining, remembering the try ... finally is actually really helpful when using the VCL TRegistry class.
Edit
I've heard that .ini files are stored in the registry in Windows, so if you want the speed advantage of ini files you should call them something else - like .cfg
This is something I've heard from an although reliable source, I haven't tested it myself.
Tim is right but an even simpler class to use is TIniRegFile but it is also more limited in what you can do.
Please see the documentation for the QSettings class from the Qt 4.5 library. It will allow you to load and store your program's configuration settings easily and in a cross-platform manner. The Windows implementation uses the Windows registry for loading and storing your program's configuration data. On other platforms, the platform's preferred, native mechanism for storing configuration data will be used. This is far better than interacting with the Windows registry directly, as you will not be tied to a specific platform.