source code file:https://github.com/mysql/mysql-server/blob/5.6/sql/item.cc#L5381
function:bool Item_field::fix_fields
guys,I am a c++ beginner.i am trying use GDB to debug mysql.
now,I have a question:
in this function Item_field::fix_fields(),i found a object called "context->first_name_resolution_table":
from_field= find_field_in_tables(thd, this,
context->first_name_resolution_table,
context->last_name_resolution_table,
reference,
thd->lex->use_only_table_context ?
REPORT_ALL_ERRORS :
IGNORE_EXCEPT_NON_UNIQUE,
!any_privileges, TRUE);
but I checked the function context.I could not find it。Can someone tell me that Why the context appear here.
thank you very much！
context comes from “this” object.
Related
My UMenuWidget (derived from UUserWidget) needs to pass a value to AMyPlayerController (derived from APlayerController).
I have tried:
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FPassParam,int,intData);
But inGameHUD->MenuWidget from AMyPlayerController::BeginPlay() returns NULL, likely because MenuWidget is yet to be created.
This prevents me from add/bind-ing of functions.
How can I do/solve this?
Kindly help me, please.
Thank you.
Link to answer, at UE4 Answer Hub:
https://answers.unrealengine.com/questions/1056641/how-to-pass-value-to-or-call-a-function-of-amyplay.html
I am trying to use an ActiveX control in my program.
QAxWidget* mAX = new QAxWidget();
mAX->setControl("{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}");
I know that there is a function:
put_ChannelType(long newValue)
But when I try to execute it:
mAX->dynamicCall("put_ChannelType(long)",2);
mAX->dynamicCall("put_ChannelType(int)",2);
mAX->dynamicCall("put_ChannelType(long)",QVariant(2));
mAX->dynamicCall("put_ChannelType(int)",QVariant(2));
I get:
QAxBase: Error calling IDispatch member put_ChannelType: Bad parameter count
Any idea what is going wrong ?
EDIT:
Weird thing is if I call
mAX->dynamicCall("put_ChannelType()");
I do not get any error message...
EDIT 2:
This also fails (as Constantin suggested)
QList<QVariant> varlist;
varlist << (int)1;
mAX->dynamicCall("put_ChannelType(int)",varlist);
Got this solved using the generateDocumentation() function.
I was using this ActiveX control in another application, but an MFC one.
It seems the function names I was referring to (which were in a machine generated IDispatch wrapper class created by VS) were not the same as the ones Qt listed.
i.e. put_ChannelType is actually SetChannelType...
Maybe this is just a version issue ?
Anyways, important part is knowing that generateDocumentation() can list you all the functions you can call with dynamicCall.
Is it OK?
mAX->dynamicCall("put_ChannelType(const QVariant &)", (long)2);
I want to use Google's Javascript Engine V8 in a project, and attempted to write a wrapper class for the engine. Parts of the Code are copied from samples/shell.cc, from the V8 Distribution.
However, it just aborts with a Segmentation fault, and I can't figure out why, although the problem is happening around v8::internal::Top::global_context() (due to an invalid context, which appears to be NULL).. The code itself looks fine to me, but maybe I did something incredibly stupid :-).
The Segmentation fault in my Code happens in v8::Script::Compile.
Code in Question (Updated): https://gist.github.com/4c28227185a14bb6288c
Thanks to Luis G. Costantini R.'s Answer, there is no longer a problem in Set (It doesn't abort anymore), however, exposed names are still not available and will result in a ReferenceError...
Thy to change v8::Context::Scope context_scope(context); from the constructor (line 134) to internal_executeString (before script = v8::Script::Compile(source, name);). That because the destructor of the class v8::Context::Scope exits from the context.
I changed the method addFunction:
void addFunction(const std::string& fname, v8::InvocationCallback func)
{
v8::HandleScope handle_scope;
std::cout << "before ::Set()" << std::endl;
v8::Context::Scope context_scope(context);
context->Global()->Set(v8::String::New(fname.c_str()),
v8::FunctionTemplate::New(func)->GetFunction());
std::cout << "after ::Set()" << std::endl;
}
The function must be added to the global object of the context used to execute the script. There is an excellent tutorial (in two parts) of V8:
http://www.homepluspower.info/2010/06/v8-javascript-engine-tutorial-part-1.html
and
http://www.homepluspower.info/2010/06/v8-javascript-engine-tutorial-part-2.html
If you try to create an instance of JavaScript Function (FunctionTemplate::GetFunction()) or JavaScript Object (ObjectTemplate::NewInstance()) before entering the context (via Context::Scope), you get the segmentation fault. The reason: there is no JavaScript context available and both Function and Object always exist in a JavaScript execution context only. As per V8 documentation:
Function:
A JavaScript function object (ECMA-262, 15.3).
Object:
A JavaScript object (ECMA-262, 4.3.3).
The stack backtrace is almost useless unless I download all the source and try to build it myself, so... :)
Change js.executeString("1+1", true, false); to js.executeString("1+1", true, true); and see what the exception handler tells you?
Looks like you just got stung by this bug, that is if you have not already taken note of it. Perhaps submit another report since the referenced one looks old. Perhaps dig a little deeper and investigate the stack frame at every function call until the Segmentation Fault is received, you could either find a work around or the fix for this bug :)
I had a similar segmentation fault and the problem turned out to be the following. I was creating a new thread and attempting to create an object template and object in that thread. Unfortunately it seems that if you create a thread, you need to make sure that you enter a v8::Context again in order to do such things.
I got it working by passing a Handle to the v8::Context::Calling to the newly created thread and entered it in the new thread by using a scope.
I wrote this here as it is the only useful thing that comes up when I do a google search for the segmentation fault.
I try use the "GetModuleFileName" to get current "setup.msi" location use mydll.dll in setup.msi installer.
But always give me "c:\windows\system\setup.msi".
Any body know why ? Plx help .
You mention C++ so I'm assuming that you are creating a Type 1 custom action as described here. If this is so, I'm guessing that you are trying to figure out where the install is occurring from so you can reference a file or something. If so, check out the MsiGetProperty function and the OriginalDatabase property. If that doesn't meet your needs checkout the the MsiSourceList* functions starting with MsiSourceListGetInfo.
So I'm trying to make use of a GtkSourceView in C++ using GtkSourceViewmm, whose documentation and level of support give me the impression that it hasn't been very carefully looked at in a long time. But I'm always an optimist :)
I'm trying to add a SourceView using some code similar to the following:
Glib::RefPtr<gtksourceview::SourceLanguageManager> source_language_manager = gtksourceview::SourceLanguageManager::create();
Glib::RefPtr<gtksourceview::SourceLanguage> source_language = Glib::wrap(gtk_source_language_manager_guess_language(source_language_manager->gobj(), file, NULL));
Glib::RefPtr<gtksourceview::SourceBuffer> source_buffer = gtksourceview::SourceBuffer::create(source_language);
gtksourceview::SourceView* = m_source_view = new gtksourceview::SourceView(source_buffer);
m_vbox.pack_start(*m_source_view);
Unfortunately, it spits out the warning
(algoviz:4992): glibmm-WARNING **:
Failed to wrap object of type
'GtkSourceLanguage'. Hint: this error
is commonly caused by failing to call
a library init() function.
and when I look at it in a debugger, indeed the second line above (the one with the Glib::wrap()) is returning NULL. I have no idea why this is, but I tried to heed the warning by adding Glib::init() to the begining of the program, but that didn't seem to help at all either.
I've tried Google'ing around, but have been unsuccessful. Does anyone know what Glib wants me to init in order to be able to make that wrap call? Or, even better, does anyone know of any working sample code that uses GtkSourceViewmm (not just regular GtkSourceView)? I haven't been able to find any actual sample code, not even on Google Code Search.
Thanks!
It turns out, perhaps not surprisingly, that what I needed to init was:
gtksourceview::init();
After this, I ran into another problem with one of the parameter to gtksourceview::SourceLanguageManager, but this was caused by a genuine bug which I subsequently reported and was promptly fixed. So everything's working great now!
I use gtkmm. Typically you have to initialize things with something like :
_GTKMain = new Gtk::Main(0, 0, false);
Of course do not forget :
delete _GTKMain;
Check here for details :
http://library.gnome.org/devel/gtkmm/2.19/classGtk_1_1Main.html
(Sorry but the link option does not work ...)