What am I doing wrong with TThread?

[Dasun]

After a good read of all the doco I could find on TThread I thought I got it and I expected the code below to work...so compiled in console mode then got the following:


Create is printed,
Then an '...AccessViolation - 45CF64'

So crashed on the create call but never executed the constructor create code.

FPC 3.0.0  & Mint latest and greatest

Code: Pascal  [Select][+][-]

1. {$mode objfpc} {H+}
2.  
3. Program runprocess ;
4.  
5. Uses
6.     cthreads ,
7. //    cmem,
8.     Process,
9.     StrUtils,
10.     SysUtils,
11.     Classes ;
12.  
13. Type
14.  
15.     n_Run_Thread = Class(TThread)
16.             Private
17.  
18.             Protected
19.                Procedure Execute; OverRide ;
20.             Public
21.                is_Output : String ;
22.  
23.                Constructor Create(ab_Suspend : Boolean) ;
24.  
25.     End ;
26.  
27.  
28. Procedure n_Run_Thread.Execute ;
29. Begin
30.  
31.     Self.is_Output := 'And Away We Go' ;
32.     Writeln(Self.is_Output) ;
33. End ;
34.  
35. Constructor n_Run_Thread.Create(ab_Suspend : Boolean);
36. Begin
37.  
38.     writeln('1');      
39.  
40.     Inherited Create(ab_Suspend) ;
41. End ;
42.  
43.  
44. Var    
45.     ln_Run_Thread : n_Run_Thread ;
46. Begin
47.  
48. writeln('Create') ;
49.  
50.   ln_Run_Thread.Create(True) ;
51.   ln_Run_Thread.Start ;
52.  
53. //writeln('Wait') ;
54. //      ln_Run_Thread.WaitFor ;
55.   FreeAndNil(ln_Run_Thread) ;
56.  
57.  
58. Writeln('Done') ;
59.  
60. End.
61.  
62. [\code]

[molly]

ln_Run_Thread.Create(True) ;

should read:
ln_Run_Thread := n_Run_Thread.Create(True) ;

Please use T prefix for type definitions. it makes things much more clear.

PS: afaik writeln is not threadsafe.

[Dasun]

OMG I am an idiot for not noticing that !!!! Should not work on a Sunday!!1

Thank you Molly - and sorry for my odd naming conventions, comes from work!

[molly]

np Dasun. it happens sometimes.

You are of course allowed to use any naming scheme you wish. Just saying that when i read:
T_Run_Thread.Create(True) ;

it immediately distinguishes from:
ln_Run_Thread.Create(True);

The latter would  then be able to obviously tell that a variable is used to try create a new instance. The former is using the right approach but doesn't store itself into a variable (which is allowed when f.i. using a with statement in front).

Using your type naming scheme was problematic (to me) simply because i am not used of having types names that are not using T prefix. You could apply the same for n_ vs ln_ but in this particular case that went wrong for you