[fpc-pascal] run pascal programs as scripts

[Mattias Gaertner]

On Sun, 27 Mar 2011 23:59:11 +0200 (CEST)
Michael Van Canneyt <michael at freepascal.org> wrote:

> 
> 
> On Sun, 27 Mar 2011, Mattias Gaertner wrote:
> 
> > On Sun, 27 Mar 2011 21:16:58 +0200 (CEST)
> > Michael Van Canneyt <michael at freepascal.org> wrote:
> >
> >>
> >>
> >> On Sun, 27 Mar 2011, Mattias Gaertner wrote:
> >>
> >>> On Sun, 27 Mar 2011 19:05:12 +0200 (CEST)
> >>> Michael Van Canneyt <michael at freepascal.org> wrote:
> >>>
> >>>>
> >>>>
> >>>> On Sun, 27 Mar 2011, Mattias Gaertner wrote:
> >>>>
> >>>>> I wrote a little tool:
> >>>>>
> >>>>> http://wiki.lazarus.freepascal.org/InstantFPC
> >>>>
> >>>> Nice job. OK to include in FPC as one of the utils ?
> >>>
> >>> Yes.
> >>
> >> Thank you. But please, fix a couple of bugs first:
> >>
> >> 1. I get a stream read error each time I execute a script the first time (i.e. it's not yet in the cache) :
> >> home: >./helloworld.pas
> >> An unhandled exception occurred at $0000000000425556 :
> >> EReadError : Stream read error
> >>    $0000000000425556
> >>    $00000000004256FA
> >>    $0000000000469E8A
> >>    $0000000000400A25
> >
> > It works here.
> 
> I assume you use FPC 2.4.x. In FPC 2.5.1 your code
> 
>    repeat
>      Count:=ss.CopyFrom(Proc.Output,4096);
>    until Count=0;
> 
> Fails.
> 
> This is because CopyFrom assumes that at least 4096 bytes are present. 
> If it doesn't get 4096 bytes, an exception is thrown.
> 
> (see recent change in trunk:
> r16992 | sergei | 2011-02-24 04:25:40 +0100 (Thu, 24 Feb 2011) | 5 lines
> 
> * Rework TStream.CopyFrom (see Mantis #17980):
> a) Use significantly larger buffer (128k instead of 1k)
> b) When Count=0, do not try to determine the source size. Just copy until the source can be read. This should improve performance with limited seek capability sources (e.g. a decompression stream will be decompressed once rather than twice).
> c) Use ReadBuffer/WriteBuffer, so an exception is raised when something goes wrong. This conforms to Delphi behavior.
> )
> 
> My FPC outputs nothing, so CopyFrom does not get 4096 bytes and therefor 
> raises an exception:
> 
> Breakpoint 1, 0x000000000041396c in fpc_raiseexception ()
> (gdb) bt
> #0  0x000000000041396c in fpc_raiseexception ()
> #1  0x0000000000425565 in CLASSES_TSTREAM_$__READBUFFER$formal$LONGINT ()
> #2  0x00000000004256fa in CLASSES_TSTREAM_$__COPYFROM$TSTREAM$INT64$$INT64 ()
> #3  0x0000000000469e8a in INSTANTFPTOOLS_COMPILE$ANSISTRING$ANSISTRING ()
> #4  0x0000000000400a25 in main ()
> 
> since the compilation is already done, the binary is in the cache, and the second run works.
> 
> Changing the code to
> 
>    buf : Array[1..4096] of byte;
> 
> begin
>    // snip
>    ss:=TStringStream.Create('');
>    repeat
>      Count:=Proc.Output.Read(Buf,4096);
>      if Count>0 then
>        ss.write(buf,count);
>    until Count=0;
> 
> it works always. Will you change it, or do I change it once it is in FPC ?

I changed it on sf.

 
> This change may affect other things in Lazarus. 
> Sergei (hope you are reading this), I think you should put this in the user_changes wiki page.


Mattias