Re: [fpc-pascal] Result: string
El 06/03/2013 13:47, Jonas Maebe escribió:
2.6.0, 2.6.2 and 2.7.1 trunk produces a warning with that code, but
with this one 2.6.0, and 2.7.1 trunk does not generate it (I do not
have 2.6.2 to test):
That's because you are passing an uninitialized value to a
var-parameter. That only generates a hint, because a lot of code uses
var-parameters also for parameters that do not yet have to be
initialized (because the code predates the existence of the "out"
keyword, or simply out of habit).
This is unrelated to string results specifically.
Hello,
I had found why I was unable to see the hint, because it is not shown
due the special contruction of the function.
This code produces a hint for the "Result: String" not initialized, but
not for the "Result: integer" one:
--
program test;
{$mode objfpc}
{$h+}
procedure TheB(var aTheA: string);
begin
aTheA:=aTheA+'A';
end;
function TheA(): string;
begin
TheB(Result);
end;
procedure TheNumberB(var aTheB: integer);
begin
aTheB:=aTheB*2;
end;
function TheNumberA: integer;
procedure HideTheHint;
begin
//As it is a procedure the "Result" var is taken
//from the function scope.
TheNumberB(Result);
end;
begin
HideTheHint;
end;
Var
C : String;
N : integer;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln('= "',C,'"');
N:=1;
N:=TheNumberA;
N:=TheNumberA;
Writeln('= "',N,'"');
end.
---
Yes, it is a bit obfuscated. I do not known if this is a bug in the hint.
--
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Re: [fpc-pascal] Result: string
El 06/03/2013 13:47, Jonas Maebe escribió: 2.6.0, 2.6.2 and 2.7.1 trunk produces a warning with that code, but with this one 2.6.0, and 2.7.1 trunk does not generate it (I do not have 2.6.2 to test): That's because you are passing an uninitialized value to a var-parameter. That only generates a hint, because a lot of code uses var-parameters also for parameters that do not yet have to be initialized (because the code predates the existence of the "out" keyword, or simply out of habit). This is unrelated to string results specifically. OK, I see now. I had changed the code to perform the same with integers and yes, it also does not report a warning only a hint which is enought to me. I'm quite sure that the library that starts this thread does not show a hint, so maybe in some situations it could fail. I'll try to reproduce it in a small code (if there is a problem, of course), meanwhile everything seems to work as expected. Thank you for your help. -- ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
On 06 Mar 2013, at 13:37, José Mejuto wrote: 2.6.0, 2.6.2 and 2.7.1 trunk produces a warning with that code, but with this one 2.6.0, and 2.7.1 trunk does not generate it (I do not have 2.6.2 to test): That's because you are passing an uninitialized value to a var- parameter. That only generates a hint, because a lot of code uses var- parameters also for parameters that do not yet have to be initialized (because the code predates the existence of the "out" keyword, or simply out of habit). This is unrelated to string results specifically. Jonas___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
El 06/03/2013 10:40, Jonas Maebe escribió:
FPC 2.6.2 does give a warning (code is from
http://bugs.freepascal.org/view.php?id=20907#c55064 ):
[...]
It could also fail in 2.6.x, just less often.
Hello,
2.6.0, 2.6.2 and 2.7.1 trunk produces a warning with that code, but with
this one 2.6.0, and 2.7.1 trunk does not generate it (I do not have
2.6.2 to test):
>\fpc\svn\bin\i386-win32\fpc test.pp
Free Pascal Compiler version 2.7.1 [2013/03/03] for i386
Copyright (c) 1993-2013 by Florian Klaempfl and others
Target OS: Win32 for i386
Compiling test.pp
Linking test.exe
26 lines compiled, 0.1 sec, 29680 bytes code, 1236 bytes data
>\fpc\fpc\2.6.0\bin\i386-win32\fpc.exe test.pp
Free Pascal Compiler version 2.6.0 [2011/12/25] for i386
Copyright (c) 1993-2011 by Florian Klaempfl and others
Target OS: Win32 for i386
Compiling test.pp
Linking test.exe
26 lines compiled, 0.0 sec , 27264 bytes code, 1692 bytes data
--
program test;
{$mode objfpc}
{$h+}
procedure TheB(var aTheA: string);
begin
aTheA:=aTheA+'A';
end;
function TheA(): string;
begin
TheB(Result);
end;
Var
C : String;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln('= "',C,'"');
end.
---
And the effect is the same as using a non initialized variable, so it
must generate a warning AFAIK. So passing Result as var does not
generate a warning.
--
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Re: [fpc-pascal] Result: string
On 05 Mar 2013, at 12:34, José Mejuto wrote: El 05/03/2013 11:23, Howard Page-Clark escribió: The code that makes me wonder something is wrong is this one: [...] For me (win32, FPC 2.6.2) the output is identical (= "A") whether or not Result in TheA() is initialised manually or not. Perhaps 2.7.1 has a regression here if it differs for you? The problem is not the different behavior as it is or will be noted in documentation, the problem is the lack of warning of using a not initialized variable, FPC 2.6.2 does give a warning (code is from http://bugs.freepascal.org/view.php?id=20907#c55064 ): $ fpc -vw tt7.pp Free Pascal Compiler version 2.6.2 [2013/02/03] for powerpc Copyright (c) 1993-2012 by Florian Klaempfl and others Target OS: Darwin for PowerPC Compiling tt7.pp tt7.pp(8,13) Warning: Function result variable does not seem to initialized Assembling (pipe) tt7.s Linking tt7 26 lines compiled, 2.6 sec 1 warning(s) issued so it is hard to fix code that works fine in 2.6.x and that could fail with Trunk. It could also fail in 2.6.x, just less often. Jonas___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
El 05/03/2013 11:23, Howard Page-Clark escribió: The code that makes me wonder something is wrong is this one: [...] For me (win32, FPC 2.6.2) the output is identical (= "A") whether or not Result in TheA() is initialised manually or not. Perhaps 2.7.1 has a regression here if it differs for you? Hello, The problem is not the different behavior as it is or will be noted in documentation, the problem is the lack of warning of using a not initialized variable, so it is hard to fix code that works fine in 2.6.x and that could fail with Trunk. Should I report a bug in Mantis about the warning ? -- ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
Am 05.03.2013 11:27, schrieb Michael Van Canneyt:
On Tue, 5 Mar 2013, Howard Page-Clark wrote:
On 04/03/13 10:33, José Mejuto wrote:
The code that makes me wonder something is wrong is this one:
---
{$mode objfpc}
{$h+}
procedure TheB(var aTheA: string);
begin
aTheA:=aTheA+'A';
end;
function TheA(): string;
begin
//Result:='';
TheB(Result);
end;
Var
C : String;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln('= "',C,'"');
end.
For me (win32, FPC 2.6.2) the output is identical (= "A") whether or
not Result in TheA() is initialised manually or not. Perhaps 2.7.1
has a regression here if it differs for you?
It is not a regression. 2.7.1 has the Delphi compatible behaviour.
Seems that we should add a remark here:
http://wiki.lazarus.freepascal.org/User_Changes_Trunk
Regards,
Sven
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Re: [fpc-pascal] Result: string
On Tue, 5 Mar 2013, Howard Page-Clark wrote:
On 04/03/13 10:33, José Mejuto wrote:
The code that makes me wonder something is wrong is this one:
---
{$mode objfpc}
{$h+}
procedure TheB(var aTheA: string);
begin
aTheA:=aTheA+'A';
end;
function TheA(): string;
begin
//Result:='';
TheB(Result);
end;
Var
C : String;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln('= "',C,'"');
end.
For me (win32, FPC 2.6.2) the output is identical (= "A") whether or not
Result in TheA() is initialised manually or not. Perhaps 2.7.1 has a
regression here if it differs for you?
It is not a regression. 2.7.1 has the Delphi compatible behaviour.
Michael.___
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Re: [fpc-pascal] Result: string
On 04/03/13 10:33, José Mejuto wrote:
The code that makes me wonder something is wrong is this one:
---
{$mode objfpc}
{$h+}
procedure TheB(var aTheA: string);
begin
aTheA:=aTheA+'A';
end;
function TheA(): string;
begin
//Result:='';
TheB(Result);
end;
Var
C : String;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln('= "',C,'"');
end.
For me (win32, FPC 2.6.2) the output is identical (= "A") whether or not
Result in TheA() is initialised manually or not. Perhaps 2.7.1 has a
regression here if it differs for you?
Howard
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Re: [fpc-pascal] Result: string
El 04/03/2013 22:16, Michael Van Canneyt escribió:
That report says the issue was assigned to Jonas and fixed in revision
20427 (ver 2.6.1).
I find the current release (2.6.2) initialises a string function
result to EmptyStr as you would hope.
[...]
Prints AA
Hello,
I'm asking because today I has updated my old 2.7.1 SVN since 8-9 months
and a library starts to fail and the "bug" was the Result string which
enters the function with a value while it does not happend in the old one.
If Result as string is not initialized a warning should be issued do not
? This happends in your simple test, but I was unable to find it in the
library that I'm using.
The code that makes me wonder something is wrong is this one:
---
{$mode objfpc}
{$h+}
procedure TheB(var aTheA: string);
begin
aTheA:=aTheA+'A';
end;
function TheA(): string;
begin
//Result:='';
TheB(Result);
end;
Var
C : String;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln('= "',C,'"');
end.
---
In this situation no warning happends and result is different if I
uncomment the "Result:='';" line.
I think the missing warning is a bug, the missing warning or the non
initialization.
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Re: [fpc-pascal] Result: string
On Mon, Mar 4, 2013 at 5:23 PM, Juha Manninen wrote: > On Mon, Mar 4, 2013 at 9:21 PM, José Mejuto wrote: >> What's the expected output of this code ? >> >> function TheA(): string; >> begin >> Result:=Result+'A'; >> end; >> >> writeln(TheA()); >> >> I thought that when the result type is an automated one its value gets >> initialized... Maybe I'm wrong... > > Yes you are wrong. It is very illogical because a local string > variable is initialized to be empty but the return value is not. > Delphi has the same problem. > > I once made even a report about it: > http://bugs.freepascal.org/view.php?id=20907 > > > Regards, > Juha Delphi would present this problem "only" in some situations (which is worse), and it didn't even show a warning when the result is a string :-/ -Flávio ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
On Mon, Mar 4, 2013 at 10:51 PM, Howard Page-Clark wrote: > That report says the issue was assigned to Jonas and fixed in revision 20427 > (ver 2.6.1). > I find the current release (2.6.2) initialises a string function result to > EmptyStr as you would hope. Ok, that sounds good. I must have misunderstood what was changed. I thought it was the warning only but apparently the fundamental issue was fixed. Juha ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
On Mon, 4 Mar 2013, Howard Page-Clark wrote:
On 04/03/13 8:23, Juha Manninen wrote:
On Mon, Mar 4, 2013 at 9:21 PM, José Mejuto wrote:
What's the expected output of this code ?
function TheA(): string;
begin
Result:=Result+'A';
end;
writeln(TheA());
I thought that when the result type is an automated one its value gets
initialized... Maybe I'm wrong...
Yes you are wrong. It is very illogical because a local string
variable is initialized to be empty but the return value is not.
Delphi has the same problem.
I once made even a report about it:
http://bugs.freepascal.org/view.php?id=20907
That report says the issue was assigned to Jonas and fixed in revision 20427
(ver 2.6.1).
I find the current release (2.6.2) initialises a string function result to
EmptyStr as you would hope.
{$mode objfpc}
{$h+}
function TheA(): string;
begin
Result:=Result+'A';
end;
Var
C : String;
begin
C:='B';
C:=TheA;
C:=TheA;
Writeln(C);
end.
Prints AA
Michael.___
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Re: [fpc-pascal] Result: string
On 04/03/13 8:23, Juha Manninen wrote: On Mon, Mar 4, 2013 at 9:21 PM, José Mejuto wrote: What's the expected output of this code ? function TheA(): string; begin Result:=Result+'A'; end; writeln(TheA()); I thought that when the result type is an automated one its value gets initialized... Maybe I'm wrong... Yes you are wrong. It is very illogical because a local string variable is initialized to be empty but the return value is not. Delphi has the same problem. I once made even a report about it: http://bugs.freepascal.org/view.php?id=20907 That report says the issue was assigned to Jonas and fixed in revision 20427 (ver 2.6.1). I find the current release (2.6.2) initialises a string function result to EmptyStr as you would hope. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Result: string
On Mon, Mar 4, 2013 at 9:21 PM, José Mejuto wrote: > What's the expected output of this code ? > > function TheA(): string; > begin > Result:=Result+'A'; > end; > > writeln(TheA()); > > I thought that when the result type is an automated one its value gets > initialized... Maybe I'm wrong... Yes you are wrong. It is very illogical because a local string variable is initialized to be empty but the return value is not. Delphi has the same problem. I once made even a report about it: http://bugs.freepascal.org/view.php?id=20907 Regards, Juha ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
[fpc-pascal] Result: string
Hello, What's the expected output of this code ? function TheA(): string; begin Result:=Result+'A'; end; writeln(TheA()); I thought that when the result type is an automated one its value gets initialized... Maybe I'm wrong... -- ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
