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trønderen wrote: In languages with a static link (I haven't been working with any more recent one than Pascal; most newer languages don't have a static link), code of an inner function may address locations in frames lower on the stack. However, they do not do this by negative offsets (or positive, if the stack is growing downwards) from their own frame pointer. Rather, they use the static link to find the stack frame of the outer function, and do relative addressing from that frame base address - as if it was a pointer to a struct. The addressing never goes outside that frame.
In the late 1970s, I had a project to optimise expression evaluation in Pascal (based on the Pascal PCode compiler). As you surmised, in the PCode compiler, accessing higher nested values from lower nested functions did skip down the stack frame back pointers (one skip per depth of nesting); but that is an implementation technique, it is not part of the language definition. I guessed that it could be improved by maintaining a vector of nested stack frame start locations to access stack specific offsets directly using this vector. This proved to be a useful optimisation for evaluating expressions. However, when I ran comparisons on a large Pascal program (my test large program was the original version of the PCode compiler) I discovered that whilst the overheads for evaluating expressions were reduced, the number of times that the test program actually accessed variables in higher scopes was so low that the overhead of maintaining the vector outweighed the advantages of having the vector.
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Branching stacks aka spaghetti stacks are used in the implementations of some functional languages. They work basically how you suggest they could work, plus the added detail of allowing "sibling frames" to exist simultaneously.
Go supposedly used to use segmented/split stacks (which also work roughly as you suggested, not on a per-frame basis exactly but more as a list of blocks), but later apparently switched to just copying the whole damn thing to keep it contiguous (which still leaves "the stack(TM)" as essentially a bunch of arraylists that exist on the heap). Other userspace-threading solutions may use similar techniques for their stacks for "fake threads", but I don't really pay attention to what happens in that space, hell I don't really know what Go is doing either, I just remembered that it did something funny and spent 5 minutes on google to look it up.
By the way, the way stacks normally use, is by reserving a bunch of contiguous virtual address space, and lazily commit pages of actual physical memory only as needed. Which is why large stack allocations involve a call to _chkstk, to ensure that every page is touched in order, to avoid missing the guard page. So already with the stack working the way it normally does, you're probably not paying the full memory cost for each stack. But there is no mechanism to shrink the stack. Once a page has been touched once, you keep it.
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If you do dynamic allocation of physical pages to a stack, each stack has a minimum memory cost of one RAM page (typically 4 Kibytes), and a similar increment. If the typical thread nests deeply, and you have a few threads, this is OK, but if you rather go for tiny, lightweight threads and lots of them, 4 Ki might lead to a lot of internal fragmentation.
One disadvantage: If you start new threads very frequently, and each start operation leads to a stack page fault, causing allocation of a new physical page and updating of MMS tables, then the cost of starting new threads, as well as the delay before the new thread is running, will increase noticeable, to phrase it politely.
Btw: I have seen such 'on demand' allocation of physical memory pages not just for stacks, but also for heap memory.
Small association: A long time ago, CPU architects were arguing whether stacks ought to grow upwards or downwards. One of the downwards arguments was that if you put the stack at the bottom of the address range, a stack overflow could be detected by an attempt to address below address zero, by the sign bit. If that logic was still in use, it would prevent an 'on demand extension' of the stack.
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trønderen wrote: One disadvantage: If you start new threads very frequently, and each start operation leads to a stack page fault, causing allocation of a new physical page and updating of MMS tables, then the cost of starting new threads, as well as the delay before the new thread is running, will increase noticeable, to phrase it politely.
That however is a architecture/design problem. Not a technical one.
Computers have limits and always will limits. So one can never create an architecture/design that is based on unlimited resources. In fact one should plan on smaller than actual resources to give one room for unexpected problems.
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I have been working on a WPF app for a client for 3 years. They have someone on site who verifies changes I make.
What I've been doing up to now is making a copy of the SQL datbase on their server, restoring to a test DB, and appling any SQL changes to it. I then copy all test files to their system into a test folder. The have a Test Mode icon on the desktop which allows them to run the test environment.
Once all changes are verified I repeate the above for their Production environment.
This has worked well, but I'd like to have a way to test different changes independently. A test environment for each branch would be nice, but that means duplicating what I wrote above for each new branch. Something really easy to set up and take down as branches change would be great.
I'm open to ideas.
If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.
modified 28-Dec-22 18:11pm.
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The above is not all that clear. Perhaps because the process has not actually been defined.
Kevin Marois wrote: What I've been doing up to now is
This is a 'deployment' or a 'release'
Kevin Marois wrote: A test environment for each branch would be nice,
Ok but what does that have to do with a 'deployment'?
Generally a branch is used to work on feature/fix/etc. So lets say right now there is a new feature and two bug fixes that you need to work on.
I am going to presume you are using source control. So locally you can work on each as a branch. When a branch is complete then you merge it to the main branch in source control. You only 'deliver' the main branch. So if you have finished the feature and one bug when you decide to deliver than you using the main branch to do that. The other bug is in the branch that is not complete and not merged.
Items in the above
1. Depending on how you deliver it you might need to rebuild the main branch. This is a process step that you would need to do. Probably should have an actual list of steps. Important step is that you should always extract from main branch even if you think it is already there.
2. SQL, or however you update the database, should be checked into source control also.
Kevin Marois wrote: now is making a copy of the SQL datbase on their server,...
Steps for testing
1. Create test database. Specific steps are irrelevant.
2. Apply NEW updates the test database.
3. Deploy NEW application to test folder. Specific steps are irrelevant.
4. The icon on desktop to test
Steps for production
1. Apply NEW updates the real database.
2. Deploy NEW application to real folder. Specific steps are irrelevant.
In the above the two steps match the appropriate previous steps except that it applies to a different destination. So you can certainly automate that using a script (linux or windows.) You can also create an application (installer) to do the same thing.
Don't forget potential errors. For example someone accidently marks a file in the real folder is read only and so your script/installer can't copy the new file in. Might just be a matter of manually inspecting the output but there are other ways.
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Flyway... I'd use Flyway.
Whether using repeatable migrations or versioned + undo you could accomplish what I'll call "feature-branched DB state management" which is what it sounds like you want.
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I know commanding and converters have been a staple of MVVM pattern and XAML interfaces, but it seems like WinUI 3 is moving away from those, particularly in terms of the functionality offered (direct binding to functions and events) and seemingly encouragement in the documentation to use them instead of commands and converters.
I'm in the middle of refactoring a WPF application to WinUI 3, and after writing several XAML pages, it looks like it's going to be possible to avoid commands and converters altogether. So is it an MVVM sin to wholly replace commands and converters with x:Bind functions?
Randy
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MS samples are meant to show language features. They don't "do MVVM" unless the article is about MVVM. x:Bind provides some additional type checking at design time and some performance advantages versus "Binding"; with trade-offs. Nothing to do with MVVM in particular.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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Thanks, Gerry. My WPF application code was fairly consistent in its application of Binding with commands and converters, and I'd like to continue that level of consistency as I refactor it to WinUI 3.
I'd like to take advantage of the x:Bind performance improvements, but also remain consistent in the way it's used. In other words, I'd prefer to continue to wholly use Binding (to DataContext) with traditional commands and converters, wholly use x:Bind (to code-behind objects) with traditional commands and converter classes, or wholly use x:Bind with functions (no commands or converters).
This may not make sense or be possible, I just haven't gotten far enough into it to tell. So far I haven't found any showstoppers, and that's why I'm curious. But I'm also only about 10% into it.
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I'm working on a WPF app that will connect to Google and retrieve contacts. Right now, the Google key info is all hardcoded unencrypted into the app and is a security risk. I'd like to refactor this so that the key is not compiled in.
One idea we had was to make a backend call to our server to retrieve the key, then use it to connect to Google.
What's the right way to do this?
If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.
modified 13-Dec-22 14:24pm.
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The server connects to / queries Google; the client makes the Google request via the server.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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OK.
THe issue is that the Security Key & Secret are stored local in the client. They have to be passed. I'm asking about how to design this for security
If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.
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But if the key is shared, shouldn't it be on the server? You route the queries through the server; the query runs from the server; the client never needs to see the key; only the results.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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You pass a Key and Secret to the server. We're trying to avoid this
If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.
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Where do I say pass the key? Put the key on the server. Why do you have a server? The client queries the server; the server queries Google and whatever else, and returns the result to the client. It acts like a proxy or a firewall. If you think "2 hops" is an issue, that's another matter, and only if you benchmark it and it says so.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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Gerry Schmitz wrote: The client queries the server; the server queries Google
It's a WPF app. It's calling the Google People API directly. The Secret and Key are hardcoded as constants in the C# code. The app directly queries the Google API passing the Secret and Key.
But that's what I said in my OP. We could store the Key & Secret on our sever and add an endpoint to simply return them, therefore removing them from the WPF app's code. The client app would still call the Google API directly passing the Secret and Key, it would just first, on app start, go to OUR server to get them, instead of them being in the code.
Old
- App starts
- App calls Google API, passing hardcoded Key & Secret
New
- App starts
- App calls OUR server, which returns the Key & Secret, and stores them
- App calls Google API, passing the stored Key & Secret
Again, the ultimate goal is to get the Secret & Key out of the code.
If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.
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Wpf <-> internet <-> server <-> internet <-> Google; UPS; USPS; VISA; etc.
I have WPF apps, running as kiosks, calling into my (ASP.NET) web server that has "no presence" other than to handle client requests), that calls multiple API's for credit card verification, postal rates, address verification, and retrieving shipping label images; all using different accounts and passwords "stored on the server" along with "back end code" and an SQL data base.
Does that help?
(Sounds like you have a simple / local "file server"; and not a remote / distributed application / database / web server).
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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Seems like the other thread has a miscommunication.
Your current app has the credential information in the client code. The type of credential information is irrelevant.
The credential information is hard-coded because you stated that. (That means every actual user of the client will be using the same exact credentials.)
So the other solution is to modify the code to do the following
1. Create a server API method that expects a requests from the client code. The client code does NOT make a call to google. The client code does not have the credentials.
2. The server code API uses the credentials and makes the call to google.
3. The server code returns the result of the google code to the client.
Note in the above that I did not specify where the server code gets the credentials from. Could be it still hard-coded but in the server code. There are other possible solutions to providing the credentials to the server code.
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I have a really strange problem with WebRequest in a ServiceStack web application (hosted by XSP on Mono). It seems that the registration of request modules works in a very strange way; I am using WebRequest to create an HTTP request, and it is failing because it was not able to find a creator for that "prefix" (HTTP).
The exception I am seeing is NotSupportedException, and I was able to track it to the fact that no creator is registered for the HTTP prefix (I am hitting https://github.com/mono/mono/blob/master/mcs/class/System/System.Net/WebRequest.cs, around line 479)
EDIT: more details: NotSupportedException is thrown by WebRequest.GetCreator, which uses the URL prefix as a key to choose which creator to return; in my case, a HttpRequestCreator. The exception is thrown because there is no creator registered for the "HTTP" prefix (actually, there are no creators at all).
So I searched around a little bit, dug into Mono sources, and found that modules are (or should be) added to the webRequestModules section of system.web in one of the various *.config files.
I looked at my machine.config file, and there it is:
System.Net.HttpRequestCreator, System, Version=4.0.0.0
Looking at WebRequest Mono sources it seems that prefixes are added from configuration(s) inside the class static constructor (not a good choice, IMHO, but still.. it should work).
To test it, I tried to add an HttpRequestCreator to system.net/webRequestModules in my web.config; this is loaded by XSP/Mono and results in a duplicate key exception (which is expected since HttpRequestCreator should be already loaded, as it is already present in machine.config).
Even stranger: if I add a mock handler for Http, like this:
bool res = System.Net.WebRequest.RegisterPrefix ("http", new MyHttpRequestCreator ());
Debug.Assert (res == false);
The assertion sometimes pass... sometimes not! (RegisterPrefix returns "false" if a creator for the same prefix is already registered; I expect it always to return false, but this is not the case! Again, it is completely random)
When the registration "fails" (i.e., returns false because an "HTTP" prefix is already registered), then the WebRequest can create requests for HTTP. It is as if calling RegisterPrefix "wakes up" the static constructor and let it run.
I am perplexed: it seems like a race condition in the execution of the static constructor of WebRequest, but this does not make sense (the runtime protects static constructors with a lock, IIRC)
What am I missing? How could I solve or work around this problem? Is it my fault (misunderstanding or missing something), or does it look like a Mono bug, so should I submit it?
modified 16-Dec-22 4:27am.
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Isaac Tack wrote: (it is not possible to reduce the amount of data).
That statement is unqualified.
You might not be able to reduce the total amount of data but you might be able to reduce the amount of data that is returned.
Isaac Tack wrote: I have the following ideas:
What happens if they want to turn off access to a user. Or change access. So the database is updated (delete the user, set a flag or change associated attributes.)
So now what happens with either of your ideas?
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It is possible to compare two git remote repositories ? Those two repositries were clone, and I need to see if the source repository was updated. I didn't see any example of how to do that ... and I am thinking its not possible ?!
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Depends what tools you're using. For the command-line, there are several suggestions in this StackOverflow thread[^].
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Ok, I see, but I don't have access to the source repository ...
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If you don't have access to it, then there's no way to know what's in it. You can't even perform a manual comparison.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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