GetSystemTime

[bkelly13]

Windows XP, Visual Studio 2008, C++
I am having a problem with this system call.

LPSYSTEMTIME   m_start;
LPSYSTEMTIME  *mp_start;
...
mp_start = &m_start;
...
GetSystemTime(  m_start );   // run time exception
GetSystemTime( &m_start );   // compile error , cannot convert  from LPSYSTEMTIME * to LPSYSTEMTIME  
GetSystemTime( *mp_start );  // run time exception
GetSystemTime(  mp_start );  // compile error, cannot convert  from LPSYSTEMTIME * to LPSYSTEMTIME

I found some example code and using that format doesn't work for me. I think I have tried all the possibilities. There must be something I don't understand. How do I get this to work?

We need to know what a dragon is
before we study its anatomy.
(Bryan Kelly, 2010)

 

[bkelly13]

On my home computer I found and ran:

SYSTEMTIME start_time;
...
GetSystemTime( &start_time );

Which works fine. I am pretty sure I obtained LPSYSTEMTIME from the help VS facility at work. Visual Studio 2008 are running on both computers. I wonder why the difference and why the LPSYSTEMTIME does not work.
I will shift to SYSTEMTIME on Monday and see how that goes.


We need to know what a dragon is
before we study its anatomy.
(Bryan Kelly, 2010)

 

[ArkM]

The OP snippet uses uninitializing pointer m_start. Of course, you have run time exception: GetSystemTime writes the value to nowhere.

 

[bkelly13]

The OP contains:

mp_start = &m_start;

If that is not a valid initialization please advise.

At work I shifted to the type SYSTEMTIME and it works as expected. A second check of the VS2008 help utility shows LPSYSTEMTIME and not SYSTEMTIME. I find that rather curious in that it differs from VS2008 that I have at home.

Mark this thread resolved.



We need to know what a dragon is
before we study its anatomy.
(Bryan Kelly, 2010)

 

[xwb]

In the original posting, you have

LPSYSTEMTIME   m_start;
LPSYSTEMTIME  *mp_start;
...
mp_start = &m_start;

Which should have given you a compile warning. The reason why you are getting a runtime exception is space. m_start is only 4 bytes long (32 bits). As you have discovered,

SYSTEMTIME m_start;
GetSystemTime (&m_start);

works because m_start now has a valid amount of space. I think that should solve your mystery.

 

[bkelly13]

Now I see my error. I was not reading carefully and did not recognize that LPSYSTEMTIME is a pointer to SYSTEMTIME. I was thinking that LPSYSTEMTIME was just a variant (one of many types, not variant as in BASIC) of the system time structure.

I could have written

SYSTEMTIME right_now;
LPSYSTEMTIME p_right_now = &right_now;

Thanks for your patience!

We need to know what a dragon is
before we study its anatomy.
(Bryan Kelly, 2010)