I think we are having an issue on using Monitor::TryEnter and Monitor::Exit on a String (I suppose this is the issue, but I'm looking for some extra information).
if (Monitor::TryEnter(m_sLogFile, 200)) {
try {
m_sLogFile = IO::Path::GetDirectoryName(Application::ExecutablePath) + "\\" + LOG_FILE_DEFAULT;
// SOME EXTRA CODE
}
finally {
Monitor::Exit(m_sLogFile);
}
}
[m_sLogFile is a String declared in my class]
The SynchronizationLockException is thrown on Monitor::Exit call, with this message:
Object synchronization method was called from an unsynchronized block
of code
I want to be sure that error is that we are locking the string and we are changing its content.
The problem is not that you are using a string for Monitor.Enter/Exit, the problem is that you are using one string for Enter and different one for Exit:
if (Monitor::TryEnter(m_sLogFile, 200)) {
try {
m_sLogFile = IO::Path::GetDirectoryName(Application::ExecutablePath) + "\\" + LOG_FILE_DEFAULT;
// SOME EXTRA CODE
}
finally {
Monitor::Exit(m_sLogFile);
}
}
See the m_sLogFile = .... inside?
You need to use a field which doesn't change (something like readonly object m_Lock; should be sufficient).
Related
I'm trying to write a very simple C# program in VS2015. I keep getting a message "The name (variable) does not exist in the current context." This is true for both my bool variable and string variable.
namespace PTouch
{
public class PTouch
{
bool lb_rc;
string strLabel;
lb_rc = false;
strLabel = "C:\BenchTop10\Standard 1in.lbx";
bpac.Document doc = new Document();
lb_rc = doc.Open("C:\BenchTop10\Standard 1in.lbx");
if lb_rc != false
{
doc.StartPrint("", 0);
doc.PrintOut(1, 0);
doc.EndPrint();
doc.Close();
}
else
{
MessageBox.Show("Open Error: " + doc.ErrorCode);
}
}
}
There are probably several problems with this code, but the first one is error about the variables not existing in the current context.
Any assistance is greatly appreciated.
I just discovered the problem... All the code has to be inside of a method, not just the class. I added a method to the class,
public void PrintLabel()
{ bool lb_rc; ... }
All errors cleared up, except MessageBox...
Thank you,
Tracy
For example, consider the following C# code:
interface IBase { void f(int); }
interface IDerived : IBase { /* inherits f from IBase */ }
...
void SomeFunction()
{
IDerived o = ...;
o.f(5);
}
I know how to get a MethodDefinition object corresponding to SomeFunction.
I can then loop through MethodDefinition.Instructions:
var methodDef = GetMethodDefinitionOfSomeFunction();
foreach (var instruction in methodDef.Body.Instructions)
{
switch (instruction.Operand)
{
case MethodReference mr:
...
break;
}
yield return memberRef;
}
And this way I can find out that the method SomeFunction calls the function IBase.f
Now I would like to know the declared type of the object on which the function f is called, i.e. the declared type of o.
Inspecting mr.DeclaringType does not help, because it returns IBase.
This is what I have so far:
TypeReference typeRef = null;
if (instruction.OpCode == OpCodes.Callvirt)
{
// Identify the type of the object on which the call is being made.
var objInstruction = instruction;
if (instruction.Previous.OpCode == OpCodes.Tail)
{
objInstruction = instruction.Previous;
}
for (int i = mr.Parameters.Count; i >= 0; --i)
{
objInstruction = objInstruction.Previous;
}
if (objInstruction.OpCode == OpCodes.Ldloc_0 ||
objInstruction.OpCode == OpCodes.Ldloc_1 ||
objInstruction.OpCode == OpCodes.Ldloc_2 ||
objInstruction.OpCode == OpCodes.Ldloc_3)
{
var localIndex = objInstruction.OpCode.Op2 - OpCodes.Ldloc_0.Op2;
typeRef = locals[localIndex].VariableType;
}
else
{
switch (objInstruction.Operand)
{
case FieldDefinition fd:
typeRef = fd.DeclaringType;
break;
case VariableDefinition vd:
typeRef = vd.VariableType;
break;
}
}
}
where locals is methodDef.Body.Variables
But this is, of course, not enough, because the arguments to a function can be calls to other functions, like in f(g("hello")). It looks like the case above where I inspect previous instructions must repeat the actions of the virtual machine when it actually executes the code. I do not execute it, of course, but I need to recognize function calls and replace them and their arguments with their respective returns (even if placeholders). It looks like a major pain.
Is there a simpler way? Maybe there is something built-in already?
I am not aware of an easy way to achieve this.
The "easiest" way I can think of is to walk the stack and find where the reference used as the target of the call is pushed.
Basically, starting from the call instruction go back one instruction at a time taking into account how each one affects the stack; this way you can find the exact instruction that pushes the reference used as the target of the call (a long time ago I wrote something like that; you can use the code at https://github.com/lytico/db4o/blob/master/db4o.net/Db4oTool/Db4oTool/Core/StackAnalyzer.cs as inspiration).
You'll need also to consider scenarios in which the pushed reference is produced through a method/property; for example, SomeFunction().f(5). In this case you may need to evaluate that method to find out the actual type returned.
Keep in mind that you'll need to handle a lot of different cases; for example, imagine the code bellow:
class Utils
{
public static T Instantiate<T>() where T : new() => new T();
}
class SomeType
{
public void F(int i) {}
}
class Usage
{
static void Main()
{
var o = Utils.Instantiate<SomeType>();
o.F(1);
}
}
while walking the stack you'll find that o is the target of the method call; then you'll evaluate Instantiate<T>() method and will find that it returns new T() and knowing that T is SomeType in this case, that is the type you're looking for.
So the answer of Vagaus helped me come up with a working implementation.
I published it on github - https://github.com/MarkKharitonov/MonoCecilExtensions
Included many unit tests, but I am sure I missed some cases.
In some cases the solver fails to find a solution for my model, which I think is there.
So I would like to populate a solution, and then check which constraint is violated.
How to do that with choco-solver?
Using choco-solver 4.10.6.
Forcing a solution
I ended up adding constraints to force variables to values of my presumed solution:
e.g.
// constraints to force given solution
vehicle2FirstStop[0].eq(model.intVar(4)).post();
vehicle2FirstStop[1].eq(model.intVar(3)).post();
nextStop[1].eq(model.intVar(0)).post();
nextStop[2].eq(model.intVar(1)).post();
...
and then
model.getSolver().showContradiction();
if (model.getSolver().solve()) { ....
Shows the first contradiction of the presumed solution, e.g.
/!\ CONTRADICTION (PropXplusYeqZ(sum_exp_49, mul_exp_51, ...
So the next step is to find out where terms such as sum_exp_49 come from.
Matching the contradiction terms with the code
Here is a simple fix for constraints which will hopefully provide enough information. We can override the post() and associates() methods of model, so that it dumps the java source filename and line number when a constraint is posted/variable is created.
Model model = new Model("Vrp1RpV") {
/**
* retrieve the filename and line number of first caller outside of choco-solver from stacktrace
*/
String getSource() {
String source = null;
StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();
// starts from 3: thread.getStackTrace() + this.getSource() + caller (post() or associates())
for (int i = 3; i < stackTraceElements.length; i++) {
// keep rewinding until we get out of choco-solver packages
if (!stackTraceElements[i].getClassName().toString().startsWith("org.chocosolver")) {
source = stackTraceElements[i].getFileName() + ":" + stackTraceElements[i].getLineNumber();
break;
}
}
return source;
}
#Override
public void post(Constraint... cs) throws SolverException {
String source=getSource();
// dump each constraint along source location
for (Constraint c : cs) {
System.err.println(source + " post: " + c);
}
super.post(cs);
}
#Override
public void associates(Variable variable) {
System.err.println(getSource() + " associates: " + variable.getName());
super.associates(variable);
}
};
This will dump things like:
Vrp1RpV2.java:182 post: ARITHM ([prop(EQ_exp_47.EQ.mul_exp_48)])
Vrp1RpV2.java:182 associates: sum_exp_49
Vrp1RpV2.java:182 post: ARITHM ([prop(mul_exp_48.EQ.sum_exp_49)])
Vrp1RpV2.java:182 associates: EQ_exp_50
Vrp1RpV2.java:182 post: BASIC_REIF ([(stop2vehicle[2] = 1) <=> EQ_exp_50])
...
From there it is possible to see where sum_exp_49 comes from.
EDIT: added associates() thanks to #cprudhom suggestion on https://gitter.im/chocoteam/choco-solver
I've got a GUI with a TabControl. Each new TabPage is created via a new Thread. I want to call this->tabControl->TabCount, but the tabControl is owned by a thread other than the one I'm calling from. Therefore, I need to Invoke a delegate. However, all the examples I find online show printing to std::cout from each of the delegate methods. I need a return value, in this case an int.
delegate int MyDel();
int InvokeTabCount()
{
if (this->InvokeRequired)
{
MyDel^ del = gcnew MyDel(this, &MyTabControl::InvokeTabCount);
auto temp = this->Invoke(del); // can't just "return this->Invoke(del)"
return temp; // Invoke() returns a System::Object^
}
else
{
return this->tabControl->TabCount;
}
}
void CreateNewTab()
{
// do stuff
this->tabControl->TabPages->Insert(InvokeTabCount() - 1, myNewTab); // insert a tab
this->tabControl->SelectTab(InvokeTabCount() - 2); // OutOfBounds and tabPageNew
}
System::Void MethodToAddNewTabPage() //actually a click event but whatever
{
System::Threading::Thread^ newThread =
gcnew System::Threading::Thread(
gcnew System::Threading::ThreadStart(this, &MyTabControl::CreateNewTab));
newThread->Start();
}
Currently, my InvokeTabCount() method is returning -1 when I simply this->Invoke(del) without returning it. And I am unable to return it because my method expects to return an int instead of a System::Object^ which is what Invoke() returns. However, when debugging I find that auto temp contains the value 2 which is correct. And temp->ToString() contains the value "2" which would also be correct.
How do I return this->Invoke(del)?
Do I need to set the value of a global variable from within my InvokeTabCount() method? I suppose I could find a way to translate from System::String^ to std::string to utilize std::stoi(), but that seems like an odd workaround.
Current solution:
delegate int MyDel();
int InvokeTabCount()
{
if (this->InvokeRequired)
{
MyDel^ del = gcnew MyDel(this, &MyTabControl::InvokeTabCount);
auto temp = this->Invoke(del);
return int::Parse(temp->ToString());
}
else
{
return this->tabControl->TabCount;
}
}
The result is an integer, boxed and contained in an Object^ reference. You should be able to simply cast it to int.
If you want to be extra safe, do a null check and verify that temp->GetType() returns int::typeid, but that's probably overkill since you're creating the delegate (still in the typed form) right there.
I have a managed bean that returns a number of different properties that describe an application. So it can be called to return the FilePath of a database by calling
appProps[sessionScope.ssApplication].helpFilePath
or
appProps[sessionScope.ssApplication].ruleFilePath
I'm trying to work out a generalized case where I need to call for the file path based on a value in a compositeData variable which can take on any one of 4 different values help/rule/app/main.
I wrote this SSJS and it works but I am wondering if there is a better way to make it work:
var target:String = compositeData.DBSource;
switch (target){
case "app" :
return appProps[sessionScope.ssApplication].appFilePath;
break;
case "help" :
return appProps[sessionScope.ssApplication].helpFilePath;
break;
case "rule" :
return appProps[sessionScope.ssApplication].ruleFilePath;
break;
case "main" :
return appProps[sessionScope.ssApplication].mainFilePath;
break;
}
I can't figure out if there is a way to compute the method by using compositeData.DBSource + "FilePath" . when I try this I get an error that the method does not exist. Using the SSJS code above is not really a problem but it just seems a bit redundant.
You can make a new method in your managed bean that takes target as an argument:
public String getFilePath(String target) {
String returnValue = "";
if (target.equalsIgnoreCase("app")) {
returnValue = this.appFilePath;
} else if (target.equalsIgnoreCase("help")) {
returnValue = this.helpFilePath;
} else if (target.equalsIgnoreCase("rule")) {
returnValue = this.ruleFilePath;
} else if (target.equalsIgnoreCase("main")) {
returnValue = this.mainFilePath;
}
return returnValue;
}
And then call it like this in your SSJS:
appProps[sessionScope.ssApplication].getFilePath(compositeData.DBSource);