Dynamic memory, Realloc in question, | Together C & C++ | Page 1

keen quest Apr 21, 2023, 1:50 PM

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messing around with it, just noticed, i have part of a code here saying c arr = (int*)realloc(arr, (size + part) * sizeof(int));
that should mean, the array size should increase by part, Right? what i get here, if just the array becomes the size of part, ill show the full code, but it is pretty long and scuffed.

sick jettyBOT Apr 21, 2023, 1:50 PM

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keen quest Apr 21, 2023, 2:01 PM

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just ping me if you reply ^^

slate acorn Apr 21, 2023, 2:12 PM

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Just paste the relevant parts where at least all the variables are defined.

keen quest Apr 21, 2023, 3:28 PM

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slate acorn Just paste the relevant parts where at least all the variables are defined.

wdym? sorry for late response btw

ripe holly Apr 21, 2023, 3:58 PM

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@keen quest Didn't understand your question clearly

keen quest Apr 21, 2023, 3:58 PM

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ok so uh

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basically arr is a pointer

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that is already allocated

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and i want to ADD more slots to it

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so uhm

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when i do something like that

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size is known and part is input btw!

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so say my length is 3, and i enter 2, it makes my array length 2 somehow

ripe holly Apr 21, 2023, 4:00 PM

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No, that is not right, because, if you enter 2, then your size will be 3+2 =5

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@keen quest

keen quest Apr 21, 2023, 4:02 PM

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thats what im saying

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i dont know why its happening

ripe holly Apr 21, 2023, 4:03 PM

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Ok so now i got your question @keen quest

keen quest Apr 21, 2023, 4:03 PM

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yeah, my bad. i didnt word it correctly

ripe holly Apr 21, 2023, 4:03 PM

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You want to make the array length equal to the inpt

ripe holly Apr 21, 2023, 4:03 PM

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ripe holly You want to make the array length equal to the inpt

correct?

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@keen quest

keen quest Apr 21, 2023, 4:04 PM

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no

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not equal

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but add it to the length

keen quest Apr 21, 2023, 4:04 PM

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ripe holly No, that is not right, because, if you enter 2, then your size will be 3+2 =5

like this

ripe holly Apr 21, 2023, 4:05 PM

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Ok got it, it should be total of both, but it is 2 instead of 5

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But how did you know that it has became 2 and not 5?

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@keen quest Can you show me where you have declared and defined size variable?

keen quest Apr 21, 2023, 4:17 PM

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uhh

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wait

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its basically

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i have a list of functions to make

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uhh

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wait

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one of them is print values

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basically

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and just i see all the values get removed

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so its easy to tell

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@ripe holly

ripe holly Apr 21, 2023, 4:18 PM

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@keen quest Ohk

keen quest Apr 21, 2023, 5:07 PM

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so uhm, what can i do about it?

ripe holly Apr 21, 2023, 5:09 PM

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@keen quest Possible reason is, value of size can be 0 due to some reason, print size before you reallocate the memory and check if size is 0 or not

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@keen quest Also, i didn't get that how did you know that it has became 2 instead of 5?

keen quest Apr 21, 2023, 5:13 PM

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because

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i have a command that prints all values

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meaning i see 5 values, after the change i get only 2 values

slate acorn Apr 21, 2023, 5:43 PM

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Do you always print the values from the most recent return value of realloc?

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Remember that realloc isn't guaranteed to return the same pointer value you give it.

sick jettyBOT Apr 22, 2023, 5:55 AM

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keen quest Apr 22, 2023, 8:49 AM

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slate acorn Remember that `realloc` isn't guaranteed to return the same pointer value you gi...

then to fix the issue, should i just make a second array to store all values? then after every realloc i just say arr = arr2 or smt

slate acorn Apr 22, 2023, 9:28 AM

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keen quest then to fix the issue, should i just make a second array to store all values? th...

No

keen quest Apr 22, 2023, 9:29 AM

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oh ive solved it, thank you though. you gave me a nice hint

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!solved

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