[Gambas-user] Variable reinitialized at each iteration of a loop structure

[Brian G]

not actually expected as p goes out of scope yet has the last value when it reenters this block, caused by the optimization taking place in the compiler. The value is of course just lucky. it seems that on mint anyway, allocated memory is always zero, in this case it looks like the register is not reused. 

"Failure is the key to success; 
each mistake teaches us something" .. Morihei Ueshiba 
Brian G 

----- On Mar 27, 2023, at 8:14 PM, Jussi Lahtinen <jussi.lahtinen at gmail.com> wrote: 

> This is quite expected (and you got a bit lucky) as you do not initialize "p",
> nor you are asking the value of "p" outside of the scope, instead you print it
> inside the loop.
> Normally compilers will give you warning about this, because uninitialized
> values may not be zero like in Gambas.
> So, at some not so lucky run value of "p" may start from some seemingly random
> number.

> Jussi

> On Tue, Mar 28, 2023 at 4:15 AM Brian G < [ mailto:brian at westwoodsvcs.com |
> brian at westwoodsvcs.com ] > wrote:

>> Hi Jussi,

>> Surprisingly this completely invalid C code compiles and actuall works the same
>> way as
>> gambas. It remebers the value of p which goes out of scope between itterations..
>> lol
>> But if you throw in a few other volitile declarations between it all goes to
>> pot....

>> #include <stdio.h>

>> int main() {
>> printf("hello world\n");
>> int i,j,k,l;
>> for(l=0; l< 2; l++) {
>> for(k=0; k < 2; k++) {
>> for(i=0;i<1000000;i++) {
>> int p;
>> p++;
>> if(p % 1000000 == 0) printf("p=%d, j=%d\n",p,j);
>> j=p;
>> }
>> printf("j=%d\n",j);
>> }
>> }
>> }
>> Output :

>> hello world
>> p=1000000, j=999999
>> j=1000000
>> p=2000000, j=1999999
>> j=2000000
>> p=3000000, j=2999999
>> j=3000000
>> p=4000000, j=3999999
>> j=4000000

>> This is a fun fact! But don't depend upon it!

>> "Failure is the key to success;
>> each mistake teaches us something" .. Morihei Ueshiba
>> Brian G

>> ----- On Mar 28, 2023, at 12:42 AM, Jussi Lahtinen < [
>> mailto:jussi.lahtinen at gmail.com | jussi.lahtinen at gmail.com ] > wrote:

>>> I think "Dim b As Integer" should be the same as "Dim b As Integer = 0". I
>>> consider this as a bug / unwanted feature.
>>> If "Dim b As Integer" is equal to a local variable declared at the beginning of
>>> a function/sub, then I think IDE should just move it there.

>>> In C variables "a" and "b" would be out of scope (valid only within the loop)
>>> and thus this would not compile and thus no confusion.

>>> Jussi

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>>> http://gambaswiki.org/wiki/doc/netiquette ] ]----

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