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This function returns a pointer to a local variable. If you want UNI.Buffer to continue to be accessible outside the function you have to allocate memory for it somehow.
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Just to extend the reply of Graham Breach:
move the
union USendLive
{
struct SSend
{
float fTestValue1;
float fTestValue2;
char cChr;
}S;
unsigned char Buffer[LIVEUNISIZE];
}UNI; to the CSendValue class ctor to make the UNI a class member.
Then your CSendValue :: SendLiveValues() would look like
unsigned char* CSendValue :: SendLiveValues()
{
float fLocalValue;
float fTest;
fTest = 190.000015f;
fLocalValue = fTest;<br />
UNI.S.cChr = 'c';<br />
UNI.S.fTestValue1 = fTest;<br />
UNI.S.fTestValue2 = 190.000015f;
return UNI.Buffer;
}
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I've been familiar with C++ for a few years now but I can't seem to think of a good solution for debugging my code. Can anyone make a suggestion?
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I should probably have mentioned. It's a class file, not a full program. I'm using Visual Studio Code and the Debugger wants an executable to run but I haven't even compiled the file.
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Then you have first to compile and link it!
BTW, is this file already a part of some project?
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You cannot test a class file in isolation, it must be part of an executable. And if you have not even compiled it yet, you are quite a way from that step. I would suggest getting a copy of Visual Studio 2017 (free from Microsoft) and using the tools that come bundled with that.
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Of course your code must first compile.
Then you could make a simple executable just for testing it, i.e. stressing the class features by fully using its public interface.
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Between your subject and your post it is not clear what you want to do.
If you want to formally 'test' your code then
1. Research unit test libraries and select one
2. Add the library to your project (not part of production delivery)
3. Use the library and write unit test code to test both happy path, boundaries and failure cases.
4. Run the unit tests.
If you want to information test your code then
1. Create ANOTHER project
2. COPY your class to it
3. Add a second class with a main method
4. Write a number of methods that exercise the code.
5. Build and run it.
6. If you make changes copy it back.
If you already know the class has a problem and you cannot not determine what the problem is
1. Find a way to replicate the problem (see two above examples.)
2. As per the other posts find a debugger and figure out how it works.
3. Step through your code in the debugger to find the problem.
Note that if you have large application and you already know that your class is failing then attempting to debug the entire application just so you get to the class is not very effective.
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Do you think is there any other or rather say faster way to remove the bug from solution! I doubt there is any. I remember when I don't know how to debug the MFC application, I used to put MessageBox to identify the pain areas. You think how many time have to run application just to point the pain location, if I know how F9,F5 and F10 work at that time, my time would be reduced by 99% in my case.
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The good news is that this isn't a homework question or comment - I'm tossing this out to C++ veterans for some direction. I'd ask in S.O. but ugh, I'm sure I'd get shamed or start a flame war on why this is a redundant question.
I cut my development teeth on C and happily moved on to C++. I have also worked in a mixed development shop for what seems like forever. Most of the UI development is in C++ of some flavor - some variant of MS depending on what tool we need to use, other tools from other vendors. However, we're always talking to embedded systems, and most of the guys are almost always pure C developers - even if the do run it through a C++ compiler  .
For the C++ code, I would love to be pure C++, especially when it comes to string handling. Current development for one side is in VS2008, and we have a mix of C++ std::wstring and CStrings (mfc). On the embedded side, usually std::wstring but mostly char bufs. I really don't care that much about the embedded side (actually I do), but I would surely love to come up with a general approach on my side.
Which leads me to the question - why is it so elephanting difficult to format a string into a buffer in standard C++? I know I can add on other libraries, but for the sake of discussion, let's say I'm not allowed to use boost, mfc, etc.
Sure, I've done my google, but it seems to me that C++ has taken purity to the level of uselessness. I'm sure I'll be burned at the stake for that, or maybe I've not found my "aha!" moment.
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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Quote: For the C++ code, I would love to be pure C++, especially when it comes to string handling.
Why would you want to avoid C library functions?
If you have a look at some STL implementations for string types, you will notice that those use C library functions like memcpy, memmove, memset, and memchr.
But you are right. I don't like the C++ string formatting too. Therefore, I never use them (besides sometimes with console output). When using other libraries like MFC, Boost, or Qt is not an option I still use [s|f][n][w]printf or the corresponding *_s versions with VS.
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No particular reason, and your point is valid that the lower level methods use these functions. I guess it's the purist in me. I have a (well it was in the past) multi-platform base of software that has a hodge-podge of string formatting code. I've got CStrings going to std::wstrings and back, which just seems silly to me. So, I said to myself, let's just use C++ and move away from mfc. Silly me.
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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I have recently been using stringstreams (<sstream> | Microsoft Docs[^]), and I have to say they are actually easier than at first sight.
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I'll take a look.
It's funny, people have been raging about string formatting in C++ for years/decades. The most common answer is "use boost", which I feel is an indictment of C++
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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charlieg wrote: "use boost", which I feel is an indictment of C++
I rather think it is, "Oh, C++ string handling looks difficult, I'll find a different library". Yes, there is a learning curve but that is true of just about everything. You can probably guess that I have never used boost. 
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Max - lol, I thought this was going to be some stand up comedy regarding formatting! I'll be sure to watch it. Good post.
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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charlieg wrote: why is it so elephanting difficult to format a string into a buffer in standard C++?
What does that mean exactly? Both 'format' and in general why would you think that something would make it easy.
As I recall as to what I think you are referring in the cases in the past if I had a specific fixed need to put/get values into a buffer then I just wrote a class that did it appropriately. It would have get/set methods that would do the correct thing for the buffer.
Then there were a couple of management methods that set the buffer up, extracted it, etc.
Similar but simpler than the way XML/Json libraries work. And long ago I created at least one implementation that did things similar too those with multiple types and I did it in C++.
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For example - suppose I want to format a log message. Beloved printf/sprintf:
sprintf(&buf[0], "Now is the time (%s) for all good %s blah blah.\r\n", GetTime(), "men");
I could add other items to the log message, say hex values, floating point with fixed # of decimal, etc. Why would you write a class for doing something like this? It's admittedly adhoc.
I'm trying to do something like this in C++, and I just don't see it. As I said, most of the hits from google are "use boost::format". I confess I just may have missed the obvious....
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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charlieg wrote: For example - suppose I want to format a log message. Beloved printf/sprintf:
sprintf(&buf[0], "Now is the time (%s) for all good %s blah blah.\r\n", GetTime(), "men");
First I wouldn't roll my own log, but that gets back to your point of not using a library.
So if no library then I would write my own log api, and it would include a varargs log methods (one for each filter type.) And I would just implement a standard varargs method to do the write.
I have done exactly that at least twice before standard log libraries existed.
charlieg wrote: Why would you write a class for doing something like this?
The examples in the past, to which I thought you might have been referring were in reference to populated a piece of binary data, for message protocols, which must have a very specific format. For example (2 byte positive int, 4 char identifier, 20 char text)
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Quote: sprintf(&buf[0], "Now is the time (%s) for all good %s blah blah.\r\n", GetTime(), "men");
That would be
ostringstream oss;
oss << "Now is the time (" << GetTime() << ") for all good " << "men" << " blah blah." << endl;
string buf = oss.str();
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Following up on this, I'll have to dig into that. That approach looks simple enough. Of course, the GetTime was a make believe function. Funny, I would think that I would have seen something like this under "Formatting Text in C++" or what have you. I'll dig for more examples.
Thanks
Charlie Gilley
<italic>Stuck in a dysfunctional matrix from which I must escape...
"Where liberty dwells, there is my country." B. Franklin, 1783
“They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.” BF, 1759
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I still use snprintf and its unicode counterpart a lot along with the variable argument versions. They work just find and are reasonably safe for my uses.
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