[SOLVED] Improvement of function SetCompileModeSwitch

[lagprogramming]

compiler/scanner.pas has function SetCompileModeSwitch(s:string; changeInit: boolean):boolean;
Within the code of the function "s:=copy(s,1,length(s)-1);" can be encountered twice. The attached patch replaces it with "setlength(s,length(s)-1);".

[AlexTP]

Reported to https://gitlab.com/freepascal.org/fpc/source/-/issues/40525

[vangli]

Hi. Just of curriosity. Isn't it?

Code: Pascal  [Select][+][-]

1. s:=copy(s,1,length(s)-1);

will guaranty that "s" is minimum an empty string if it happens that "s" is single byte or already an empty string.

Code: Pascal  [Select][+][-]

1. setlength(s,length(s)-1);

will release memory if "s" is one byte long or already an empty string. Then the rest of the function SetCompileModeSwitch will crash?

[TRon]

will release memory if "s" is one byte long or already an empty string. Then the rest of the function SetCompileModeSwitch will crash?

Nah, not really 

Code: Pascal  [Select][+][-]

1. case s[length(s)] of
2.  

[vangli]

Thks TRon. I may have been (mis)leaded by https://www.freepascal.org/docs-html/rtl/system/setlength.html where it states the following:

"Note that SetLength is governed by the Copy-On-Write principle for strings and dynamic arrays: the reference count after a call to SetLength will be 1 (except when the length is zero, then the array is removed from memory). "

I read the parenthesis to include both strings and arrays, but it may only be true for array length.