Hi,
even if there's closed issue
https://bugs.freepascal.org/view.php?id=34169 I would like to ask if
it can be reconsidered.
The subject is that SetLength now gives warning: Variable "dynamic
array" of a managed type does not seem to be initialized
in 3.3.1 and 3.1.1 while it doesn't give any warning in stable 3.0.4
seriously that is such a bullshit warning.
SetLength is called to initialize the variable, of course the variable
is not initialized before. If it was initialized, we might not even need
to call SetLength
Cheers,
Benito
Am 04.09.18 um 15:53 schrieb Vojtěch Čihák:
Hello,
even if there's closed issue
https://bugs.freepascal.org/view.php?id=34169 I would like to ask if
it can be reconsidered.
The subject is that SetLength now gives warning: Variable "dynamic
array" of a managed type does not seem to be initialized
in 3.3.1 and 3.1.1 while it doesn't give any warning in stable 3.0.4
As a solution is recommended do declaration: var arr: array of
widechar = ();
But it means that initialization is in fact done twice. See assembler
of following code:
procedure TForm1.Button1Click(Sender: TObject);
var DA: array of widechar = ();
begin
SetLength(DA, 10);
writeln(DA[0]);
end;
unit1.pas:30 var DA: array of widechar = ();
00000000004696C9 488d1538536600 lea 0x665338(%rip),%rdx
# 0xacea08 <RTTI_$UNIT1_$$_def00000138>
00000000004696D0 488b3529536600 mov 0x665329(%rip),%rsi
# 0xacea00 <TC_$UNIT1$_$TFORM1_$_BUTTON1CLICK$TOBJECT_$$_defaultDA>
00000000004696D7 4889e7 mov %rsp,%rdi
00000000004696DA e8d199fcff callq 0x4330b0
<fpc_dynarray_assign>
unit1.pas:32 SetLength(DA, 10);
00000000004696DF 48c74424680a000000 movq $0xa,0x68(%rsp)
00000000004696E8 488d3519536600 lea 0x665319(%rip),%rsi
# 0xacea08 <RTTI_$UNIT1_$$_def00000138>
00000000004696EF 488d4c2468 lea 0x68(%rsp),%rcx
00000000004696F4 4889e7 mov %rsp,%rdi
00000000004696F7 ba01000000 mov $0x1,%edx
00000000004696FC e8df99fcff callq 0x4330e0
<fpc_dynarray_setlength>
unit1.pas:33 writeln(DA[0]);
To avoid warning we now need four extra instructions incl. call to
fpc_array_assign, which is obviously redundant.
As an explanation is written: Setlength uses a var parameter. This is
no different from other cases of var parameter usage.
I disaggre here, because SetLength is not an usual procedure, it is
fundamental part of compiler. Therefore it deserves some exception.
That's why I ask for reconsidering and make it behave like in 3.0.4 or
change declaration from "var" to "out" as it is done in getmem().
Thanks, Vojtěch.
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