Good day good-looking computer people,
I might be asking a bit too much, but here it goes.
I'm trying to do a bit of reserve engineering on this sound library. Looking at the main.cpp file (which I have posted below) it has two methods, setup and play. I'm a bit confused as to how this is working:
When you run the Xcode project, shouldn't there be a main function that is the first method called? I don't see that here.
The play function is being called (because I hear music), but it must be from elsewhere since in needs the argument output. Where could it be being called from?
To try to be a bit more specific, this is my question:
If the program isn't starting from a main method in the main.cpp file, where else could it be starting from ?
#include "maximilian.h"
double outputs[2],moreoutputs[2]; //some track outputs
double filtered, ramped, filtered2;
osc buffertest,ramp;
mix mymix,bobbins;//some panning busses
double env[4]={200,0,0,50};//the kick drum pitch envelope data
double env2[6]={10000,0,9000,5,0,5};//the hi hat pitch envelope dat
envelope b,f;//two envelopers
sample beats;
extern int channels=2;//stereo-must be supported by hardware
extern int buffersize=256;//should be fine for most things
extern int samplerate=44100;//SR must be supported by card. It's always the default
void setup() {//some inits
b.amplitude=env[0];//starting value for envelope b
f.amplitude=env2[0];//same for f
beats.load("/Users/ericbrotto/Desktop/beats.wav");//put a path to a soundfile here. Wav format only.
printf("Summary:\n%s", beats.getSummary());//get info on samples if you like
}
void play(double *output) {//this is where the magic happens. Very slow magic.
filtered2=beats.play(1*(1./34), 0, beats.length());
bobbins.stereo(filtered2, moreoutputs, 0.5);//invert the pan
output[0]=outputs[0]+moreoutputs[0];//stick it in the out!!
output[1]=outputs[1]+moreoutputs[1];
}
Thanks!
If the program isn't starting from a
main method in the main.cpp file,
where else could it be starting from ?
From a main method in a different source file or pre-compiled library, probably, or definitely.
A main method is required and must have the name main unless you tell the compiler otherwise. It is possible that the main method gets included through a header or is implemented by a macro.
in the directory where you unpacked the library -
find . | xargs egrep "main"
It has to be there somewhere... ;)
You're dealing with a library, not a standalone program. It doesn't have a main function, since it won't run on its own. When a developer uses a library, such as this, his application calls out to the library's functions (such as play).
I don't entirely understand from what you hear music. What have you compiled? An example program? In that case, that example program probably does have a main function and at some point calls the library's play.
main is either getting defined in the the maximillian.h, something it includes, or it is already compiled into the maximillian library.
Put a breakpoints on the front of each function, run the app, and examine call stack when breakpoint is hit.
what i understand from it is the cpp file for the implementation of this library's header it is not a complete program but when you use this lib in your program you have to do is
1) use its setup method to setup or load the file u want to play
2) you have to call play to play the sound
that it about this/.
For your question
If the program isn't starting from a main method in the main.cpp file,
where else could it be starting from
?
Global objects and static members of classes will be initialized before call to main() function.
For below code
class Test
{
public:
};
Test* fun()
{
return new Test;
}
Test *p = fun();
int main()
{
}
For initializing pointer p, fun() will be called before main() function.
Line 491 of maximillian.cpp
Related
Aside from recompiling rt.jar is there any way I can replace the currentTimeMillis() call with one of my own?
1# The right way to do it is use a Clock object and abstract time.
I know it but we'll be running code developed by an endless number of developers that have not implemented Clock or have made an implementation of their own.
2# Use a mock tool like JMockit to mock that class.
Even though that only works with Hotspot disabled -Xint and we have success using the code bellow it does not "persist" on external libraries. Meaning that you'd have to Mock it everywhere which, as the code is out of our control, is not feasible. All code under main() does return 0 milis (as from the example) but a new DateTime() will return the actual system millis.
#MockClass(realClass = System.class)
public class SystemMock extends MockUp<System> {
// returns 1970-01-01
#Mock public static long currentTimeMillis() { return 0; }
}
3# Re-declare System on start up by using -Xbootclasspath/p (edited)
While possible, and though you can create/alter methods, the one in question is declared as public static native long currentTimeMillis();. You cannot change it's declaration without digging into Sun's proprietary and native code which would make this an exercise of reverse engineering and hardly a stable approach.
All recent SUN JVM crash with the following error:
EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00000, pid=4668, tid=5736
4# Use a custom ClassLoader (new test as suggested on the comments)
While trivial to replace the system CL using -Djava.system.class.loader JVM actually loads up the custom classLoader resorting to the default classLoader and System is not even pushed trough the custom CL.
public class SimpleClassLoader extends ClassLoader {
public SimpleClassLoader(ClassLoader classLoader) {
super(classLoader);
}
#Override
public Class<?> loadClass(String name) throws ClassNotFoundException {
return super.loadClass(name);
}
}
We can see that java.lang.System is loaded from rt.jar using java -verbose:class
Line 15: [Loaded java.lang.System from C:\jdk1.7.0_25\jre\lib\rt.jar]
I'm running out of options.
Is there some approach I'm missing?
You could use an AspectJ compiler/weaver to compile/weave the problematic user code, replacing the calls to java.lang.System.currentTimeMillis() with your own code. The following aspect will just do that:
public aspect CurrentTimeInMillisMethodCallChanger {
long around():
call(public static native long java.lang.System.currentTimeMillis())
&& within(user.code.base.pckg.*) {
return 0; //provide your own implementation returning a long
}
}
I'm not 100% sure if I oversee something here, but you can create your own System class like this:
public static class System {
static PrintStream err = System.err;
static InputStream in = System.in;
static PrintStream out = System.out;
static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length) {
System.arraycopy(src, srcPos, dest, destPos, length);
}
// ... and so on with all methods (currently 26) except `currentTimeMillis()`
static long currentTimeMillis() {
return 4711L; // Your application specific clock value
}
}
than import your own System class in every java file. Reorganize imports in Eclipse should do the trick.
And than all java files should use your applicatikon specific System class.
As I said, not a nice solution because you will need to maintain your System class whenever Java changes the original one. Also you must make sure, that always your class is used.
As discussed in the comments, it is possible that option #3 in the original question has actually worked, successfully replacing the default System class.
If that is true, then application code which calls currentTimeMillis() will be calling the replacement, as expected.
Perhaps unexpectedly, core classes like java.util.Timer would also get the replacement!
If all of the above are true, then the root cause of the crash could be the successful replacement of the System class.
To test, you could instead replace System with a copy that is functionally identical to the original to see if the crashes disappear.
Unfortunately, if this answer turns out to be correct, it would seem that we have a new question. :) It might go like this:
"How do you provide an altered System.currentTimeMillis() to application classes, but leave the default implementation in place for core classes?"
i've tried using javassist to remove the native currentTimeMills, add a pure java one and load it using bootclasspath/p, but i got the same exception access violation as you did. i believe that's probably because of the native method registerNatives that's called in the static block but it's really too much to disassemble the native library.
so, instead of changing the System.currentTimeMills, how about changing the user code? if the user code already compiled (you don't have source code), we can use tools like findbugs to identify the use of currentTimeMillis and reject the code (maybe we can even replace the call to currentTimeMills with your own implementation).
I think this would increase the quality of life when devving, but google came up with nothing and I couldn't find anything specific inside inside Netbeans either.
What I want is to start with this header:
class bla
{
public:
static void gfg(somearg asd);
};
Then I open the blank bla.cpp and pressed 'autoimplement'. After that, it would look like this:
#include "bla.h"
static void bla::gfg(somearg asd)
{
//TODO: implement
throw unimplemented("void bla::gfg(somearg) is unimplemented");
}
Anyone know of a tool like this?
I found http://www.radwin.org/michael/projects/stubgen/
"stubgen is a C++ development tool that keeps code files in sync with their associated headers. When it finds a member function declaration in a header file that doesn't have a corresponding implementation, it creates an empty skeleton with descriptive comment headers."
This looks like it does exactly what you want it to do.
Some time has passed and in the meantime the requested feature seems to have been implemented in netbeans. Refer to https://netbeans.org/bugzilla/show_bug.cgi?id=213811 , which also gives a description on how to use it:
Note:
Implemented CTRL+SPACE.
IDE suggest implementing of class method if CTRL+SPACE was pressed:
- inside file that already has at least one method definition
- between method declarations
Yes I am a begginer. I am reading a book on cocos2d development. The author wrote this book using 0.99.4. In the book, it says to call a function that creates sprites and adds them to an array by using the following code: [self initSpiders];. But when I run this, I get a warning that says "'Gamescene may not respond to'-resetSpiders'". I am assuming that there is an updated way of doing this in the newer version of cocos2d. If there is, I would be thankful if someone could explain the proper way of going about this. If this is the correct way, then what am I doing wrong? Thanks in advance.
In objective-c, an object tells a message to do something:
[someObject doSomething];
Or with an argument:
[someObject doSomethingWithArgument:someValue];
The message you get from the compiler is telling you that the object (eg. "someObject") does not understand what you are telling it to do (doSomething).
To make that compiler warning go away, check the following:
Did you #include the header file of the class your "someObject" is an instance of?
Does that header file in fact have the method you are calling? (including arguments?)
If you are calling a method you wrote, make sure you put that method in the header file. If you are calling a method that someone else wrote, or is part of the OS; make sure you include the header file, then perhaps find the method in the header file and copy/paste it into your code. This will make sure you get the EXACT method signature. These two are not the same:
[self generateSprites]; // note the capitol S
[self generatesprites]; // method names are case sensitive
If you need a better answer, you'll need to post some of your code so that people can see what you're doing wrong.
This is a weird question in that I'm not sure where to start looking.
First of all, I haven't done any C++ programming for the last 10 years so it could be me thats forgotten a few things. Secondly, the IDE I'm using is Eclipse based (which I've never used) and customized for Samsung bada based mobile development (it kicks off an emulator for debugging purposes)
I'm posting my code samples as images because the StackOverflow WYSIWYG editor seems to have a problem parsing C++.
[EDIT] Due to complaints I've edited my question to remove the images. Hope that helps :)
I have the following header file...
#include <FApp.h>
#include <FBase.h>
#include <FGraphics.h>
#include <FSystem.h>
#include <FMedia.h>
using namespace Osp::Media;
using namespace Osp::Graphics;
class NineAcross :
public Osp::App::Application,
public Osp::System::IScreenEventListener
{
public:
static Osp::App::Application* CreateInstance(void);
public:
NineAcross();
~NineAcross();
public:
bool OnAppInitializing(Osp::App::AppRegistry& appRegistry);
private:
Image *_problematicDecoder;
};
...and the following cpp file...
#include "NineAcross.h"
using namespace Osp::App;
using namespace Osp::Base;
using namespace Osp::System;
using namespace Osp::Graphics;
using namespace Osp::Media;
NineAcross::NineAcross()
{
}
NineAcross::~NineAcross()
{
}
Application* NineAcross::CreateInstance(void)
{
// Create the instance through the constructor.
return new NineAcross();
}
bool NineAcross::OnAppInitializing(AppRegistry& appRegistry)
{
Image *workingDecoder;
workingDecoder->Construct();
_problematicDecoder->Construct();
return true;
}
Now, in my cpp file, if I comment out the line that reads _problematicDecoder->Construct();...I'm able to set a breakpoint and happily step over the call to Constuct() on workingDecoder. However, as soon as I uncomment the line that reads _problematicDecoder->Construct();... I end up with the IDE telling me...
"No source available for "Osp::Media::Image::Construct()"
In other words, why can I NOT debug this code when I reference Image *image from a header file?
Any ideas?
Thanks :-)
This usually means you're stepping through some code which you do not posses its source.
I assume here that Osp::Media::Image is a class supplied by Samsung or similar for which you do not have the cpp file. So this means the debugger can't show you the current code line while you're at a function of Osp::Media::Image.
Alternatively, there's a good chance you do have all of the source code for this class, but Eclipse doesn't know where it is. In this case you can add the correct directories under the Debug Configurations window.
Ok, problem solved.
The idea is to first new up an instance of Image like so...
_decoder = new Osp::Media::Image();
And then do _decoder->Construct().
Funny enough, this seems blatantly obvious to me now coming from the C# world, though why the code I posted for workingDecoder works is still somewhat mysterious to me. The fact the sample projects pre-loaded with the bada IDE don't seem to make a call to new() leads me to believe that perhaps those samples are outdated our out of synch.
Either that or I really AM wildly out of the C++ loop.
Anyway thanks so much for the effort guys.
Appreciated :)
I've successfully loaded a C++ plugin using a custom plugin loader class. Each plugin has an extern "C" create_instance function that returns a new instance using "new".
A plugin is an abstract class with a few non-virtual functions and several protected variables(std::vector refList being one of them).
The plugin_loader class successfully loads and even calls a virtual method on the loaded class (namely "std::string plugin::getName()".
The main function creates an instance of "host" which contains a vector of reference counted smart pointers, refptr, to the class "plugin". Then, main creates an instance of plugin_loader which actually does the dlopen/dlsym, and creates an instance of refptr passing create_instance() to it. Finally, it passes the created refptr back to host's addPlugin function. host::addPlugin successfully calls several functions on the passed plugin instance and finally adds it to a vector<refptr<plugin> >.
The main function then subscribes to several Apple events and calls RunApplicationEventLoop(). The event callback decodes the result and then calls a function in host, host::sendToPlugin, that identifies the plugin the event is intended for and then calls the handler in the plugin. It's at this point that things stop working.
host::sendToPlugin reads the result and determines the plugin to send the event off to.
I'm using an extremely basic plugin created as a debugging plugin that returns static values for every non-void function.
Any call on any virtual function in plugin in the vector causes a bad access exception. I've tried replacing the refptrs with regular pointers and also boost::shared_ptrs and I keep getting the same exception. I know that the plugin instance is valid as I can examine the instance in Xcode's debugger and even view the items in the plugin's refList.
I think it might be a threading problem because the plugins were created in the main thread while the callback is operating in a seperate thread. I think things are still running in the main thread judging by the backtrace when the program hits the error but I don't know Apple's implementation of RunApplicationEventLoop so I can't be sure.
Any ideas as to why this is happening?
class plugin
{
public:
virtual std::string getName();
protected:
std::vector<std::string> refList;
};
and the pluginLoader class:
template<typename T> class pluginLoader
{
public: pluginLoader(std::string path);
// initializes private mPath string with path to dylib
bool open();
// opens the dylib and looks up the createInstance function. Returns true if successful, false otherwise
T * create_instance();
// Returns a new instance of T, NULL if unsuccessful
};
class host
{
public:
addPlugin(int id, plugin * plug);
sendToPlugin(); // this is the problem method
static host * me;
private:
std::vector<plugin *> plugins; // or vector<shared_ptr<plugin> > or vector<refptr<plugin> >
};
apple event code from host.cpp;
host * host::me;
pascal OSErr HandleSpeechDoneAppleEvent(const AppleEvent *theAEevt, AppleEvent *reply, SRefCon refcon) {
// this is all boilerplate taken straight from an apple sample except for the host::me->ae_callback line
OSErr status = 0;
Result result = 0;
// get the result
if (!status) {
host::me->ae_callback(result);
}
return status;
}
void host::ae_callback(Result result) {
OSErr err;
// again, boilerplate apple code
// grab information from result
if (!err)
sendToPlugin();
}
void host::sendToPlugin() {
// calling *any* method in plugin results in failure regardless of what I do
}
EDIT: This is being run on OSX 10.5.8 and I'm using GCC 4.0 with Xcode. This is not designed to be a cross platform app.
EDIT: To be clear, the plugin works up until the Apple-supplied event loop calls my callback function. When the callback function calls back into host is when things stop working. This is the problem I'm having, everything else up to that point works.
Without seeing all of your code it isn't going to be easy to work out exactly what is going wrong. Some things to look at:
Make sure that the linker isn't throwing anything away. On gcc try the compile options -Wl -E -- we use this on Linux, but don't seem to have found a need for it on the Macs.
Make sure that you're not accidentally unloading the dynamic library before you've finished with it. RAII doesn't work for unloading dynamic libraries unless you also stop exceptions at the dynamic library border.
You may want to examine our plug in library which works on Linux, Macs and Windows. The dynamic loading code (along with a load of other library stuff) is available at http://svn.felspar.com/public/fost-base/trunk/
We don't use the dlsym mechanism -- it's kind of hard to use properly (and portably). Instead we create a library of plugins by name and put what are basically factories in there. You can examine how this works by looking at the way that .so's with test suites can be dynamically loaded. An example loader is at http://svn.felspar.com/public/fost-base/trunk/fost-base/Cpp/fost-ftest/ftest.cpp and the test suite registration is in http://svn.felspar.com/public/fost-base/trunk/fost-base/Cpp/fost-test/testsuite.cpp The threadsafe_store holds the factories by name and the suite constructor registers the factory.
I completely missed the fact that I was calling dlclose in my plugin_loader's dtor and for some reason the plugins were getting destructed between the RunApplicatoinEventLoop call and the call to sendToPlugin. I removed dlclose and things work now.