Re: [fpc-devel] Evaluation order in expressions
On 30.07.2019 09:46, Michael Van Canneyt wrote: I think they updated the documentation meanwhile: http://docwiki.embarcadero.com/RADStudio/Rio/en/Procedures_and_Functions_(Delphi)#Calling_Conventions So you can see it depends on the calling convention. Thanks, I wasn't aware of it! Ondrej ___ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On Tue, 30 Jul 2019, Ondrej Pokorny wrote: On 30.07.2019 08:55, Jonas Maebe wrote: Delphi evaluates e.g. all parameters to subroutine calls from left to right, which FPC does not guarantee. If I am not mistaken Delphi doesn't guarantee this either. I remember I "learned it by doing" quite some time ago and I don't think I used FPC at that point, so it must have been Delphi. A quick Google search revealed https://stackoverflow.com/a/11010685 - yes, when I run the code from the answer in Delphi 32bit the right "SideEffect(2)" call is executed before the left "SideEffect(1)" call. I think they updated the documentation meanwhile: http://docwiki.embarcadero.com/RADStudio/Rio/en/Procedures_and_Functions_(Delphi)#Calling_Conventions So you can see it depends on the calling convention. Michael. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On 30.07.2019 08:55, Jonas Maebe wrote: Delphi evaluates e.g. all parameters to subroutine calls from left to right, which FPC does not guarantee. If I am not mistaken Delphi doesn't guarantee this either. I remember I "learned it by doing" quite some time ago and I don't think I used FPC at that point, so it must have been Delphi. A quick Google search revealed https://stackoverflow.com/a/11010685 - yes, when I run the code from the answer in Delphi 32bit the right "SideEffect(2)" call is executed before the left "SideEffect(1)" call. Ondrej ___ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On 2019-07-30 08:23, Ondrej Pokorny wrote: can somebody comment on the Remark from https://www.freepascal.org/docs-html/ref/refch12.html ? _Remark: The order in which expressions of the same precedence are evaluated is not guaranteed to be left-to-right._ Is this valid for boolean expressions, too? Only if short circuit boolean evaluation is off. (Well it is no surprise because https://www.freepascal.org/docs-html/ref/refch12.html states that "_This behaviour is distinctly different from Delphi or Turbo Pascal._") Delphi evaluates e.g. all parameters to subroutine calls from left to right, which FPC does not guarantee. Jonas ___ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On Tue, 30 Jul 2019, Ondrej Pokorny wrote: On 30.07.2019 08:33, Michael Van Canneyt wrote: The documentation has already been fixed in this regard, there was a bugreport about it not so long ago. Great, thank you. Is there some online version of the latest documentation trunk (nightly build)? No, there is not... Michael. ___ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On 30.07.2019 08:33, Michael Van Canneyt wrote: The documentation has already been fixed in this regard, there was a bugreport about it not so long ago. Great, thank you. Is there some online version of the latest documentation trunk (nightly build)? Ondrej ___ fpc-devel maillist - fpc-devel@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On Tue, 30 Jul 2019, Ondrej Pokorny wrote:
On 30.07.2019 08:23, Ondrej Pokorny wrote:
/Remark: The order in which expressions of the same precedence are
evaluated is not guaranteed to be left-to-right./
Is this valid for boolean expressions, too? I use the following construct
with {$BOOLEVAL OFF}:
Result := Assigned(MyObject) and (MyObject.Value>5);
A moment of relief. The FPC compiler itself depends on the left-to-right
evaluation. E.g. compiler/aoptbase.pas, line 284:
while assigned(p1) and assigned(p2) and GetNextInstruction(p1,p1) and
(p1<>p2) do
So is the documentation wrong or are the compiler (and also my own) sources
flawed?
The documentation has already been fixed in this regard, there was a
bugreport about it not so long ago.
Michael.___
fpc-devel maillist - fpc-devel@lists.freepascal.org
https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
Re: [fpc-devel] Evaluation order in expressions
On 30.07.2019 08:23, Ondrej Pokorny wrote:
/Remark: The order in which expressions of the same precedence are
evaluated is not guaranteed to be left-to-right./
Is this valid for boolean expressions, too? I use the following
construct with {$BOOLEVAL OFF}:
Result := Assigned(MyObject) and (MyObject.Value>5);
A moment of relief. The FPC compiler itself depends on the left-to-right
evaluation. E.g. compiler/aoptbase.pas, line 284:
while assigned(p1) and assigned(p2) and GetNextInstruction(p1,p1)
and (p1<>p2) do
So is the documentation wrong or are the compiler (and also my own)
sources flawed?
Best
Ondrej
___
fpc-devel maillist - fpc-devel@lists.freepascal.org
https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
[fpc-devel] Evaluation order in expressions
Hello,
can somebody comment on the Remark from
https://www.freepascal.org/docs-html/ref/refch12.html ?
/Remark: The order in which expressions of the same precedence are
evaluated is not guaranteed to be left-to-right./
Is this valid for boolean expressions, too? I use the following
construct with {$BOOLEVAL OFF}:
Result := Assigned(MyObject) and (MyObject.Value>5);
The remark above suggests that I cannot use it because
(MyObject.Value>5) may be evaluated before Assigned(MyObject) if the
optimizer decides so.
On the other hand, the information in
https://www.freepascal.org/docs-html/current/prog/progsu4.html#x11-11.2.4
suggests the opposite:
/So, in the following example, the function Bofu, which has a boolean
result, will never get called.//
//If False and Bofu then/
Delphi documentation also explicitly states that the expressions are
evaluated in left to right order:
http://docwiki.embarcadero.com/RADStudio/Rio/en/Boolean_short-circuit_evaluation_(Delphi_compiler_directive)
(Well it is no surprise because
https://www.freepascal.org/docs-html/ref/refch12.html states that "/This
behaviour is distinctly different from Delphi or Turbo Pascal./")
Ondrej
___
fpc-devel maillist - fpc-devel@lists.freepascal.org
https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
