Valgrind memory error: uninitialized value

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Hi all!

I have following code in my C++ project:

object *d = reinterpret_cast<object *>(it -> second);
d -> type = MINIGAMEZ_TYPE_OBJECT;
d -> value = map<string, void *>();

where it -> second is memory allocated with the help of malloc().
After that this memory is being used by another functions in my code. When testing with valgrind it says that I am using uninitialized values. Since this is only error in my project I would like to get rid of it.

Posted 15-Aug-10 21:30pm

Nyarost

Updated 16-Aug-10 4:53am

v3

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Richard MacCutchan · Answer 1 · 2010-08-15T21:51:00

Solution 1

Quote: "Since this is only error in my project I would like to get rid of it. ".

And what exactly do you expect us to do to make that happen? If you are using a value or values that have not been initialised then you need to fix your program to correct it. We cannot guess where the error may be.

Posted 15-Aug-10 21:51pm

Richard MacCutchan

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Nyarost 16-Aug-10 3:54am

Wait wait wait!

I initialize values:

d -> type = MINIGAMEZ_TYPE_OBJECT;
d -> value = map<string, void *>();

Without this really doesn't work. Segmentation fault appears and so on. With this two lines everything works just great. No errors, no leaks, no faults. Only valgrind report.

Aescleal · Answer 2 · 2010-08-15T22:31:00

Solution 2

The following answer was posted looking at the original code the user posted. It's pretty meaningless as he's changed the code.

It wouldn't surprise me if the problem was in the first line of the snippet you've posted. You're casting a pointer to an object. Try replacing the reinterpret_cast with a static_cast and then fixing what the compiler tells you is wrong.

[Actually on most of the compiler I use I doubt the first line would compile on high warnings and treat warnings as errors (/W4 /WX). Try cranking the warning level up a bit and see what happens.]

Oh, and don't use malloc unless a C library you're linking with requires the memory to be malloced.

Cheers,

Ash

Posted 15-Aug-10 22:31pm

Aescleal

Updated 16-Aug-10 5:32am

v4

Comments

Nyarost 16-Aug-10 4:34am

Thanks for your answer!

About all the things you've mentioned:
1. I have -Wall and -Werror flags set in gcc. It compiles.
2. malloc is only choise here :(

Konstantin

Aescleal 16-Aug-10 9:40am

I doubt malloc is the only choice - if it is how're std::string and std::map working?

Did fixing the reinterpret_cast do anything?

PS: Just tested the code you presented on gcc 3.4.4 and got the error:

invalid reinterpret_cast from type `void*' to type `object'

at the first line which I expected from reading your code.

Nyarost 16-Aug-10 10:41am

I use gcc 4.4.3 and it is ok for me. If i use memcpy, the memory is said to be initialixed. If I init object members `by hand` valgrind gives an error. I have std::map which contains a lot of objects of mixed type: so i use void *. When I need to place an object in this map, I allocate memory and memcpy the data or in case of `object` type initialize values.

Nyarost 16-Aug-10 10:45am

Actually it is strange that gcc doesn't compile cause reinterpret_cast changes one data type into another. It should be used to cast between incompatible pointer types.

http://www.cppreference.com/wiki/keywords/reinterpret_cast

Nyarost 16-Aug-10 10:53am

Noticed incorrectness in posted code. There should be object * instead of object. That's why your gcc throws an error.