Seg Fault

[terse sparrow]

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[tulip summit]

Could you try to compile and run with address sanitizer enabled? That should tell you what line the segfault is occurring on

[terse sparrow]

Address Sanitizer

Memory errors in C and C++ are easy to make and they can be very hard to debug because they can manifest far from their source. Address sanitizer is a runtime checker that identifies memory errors at their source and makes debugging much simpler. Address sanitizer is available for gcc/clang on linux and msvc on windows. To use it simply pass -fsanitize=address to the compiler.

Note: Make sure to turn on debug symbols with -g for gcc/clang and -Zi for msvc.

Example

How to read sanitizer output

The first few lines tell you the problem, heap-use-after-free, due to performing a READ of size 4, at example.c line 7 (from the first line of the stack trace).

==1==ERROR: AddressSanitizer: heap-use-after-free on address ....
READ of size 4 at 0x602000000010 thread T0
    #0 0x40120f in main /app/example.c:7
    #1 0x7fda58629d8f  (...)
    #2 0x7fda58629e3f in __libc_start_main (...)
    #3 0x4010b4 in _start (...)

Additional information is also included such as where the allocation was performed and where the allocation was freed.

See Also

• Other sanitizers exist and can be similarly helpful, including ubsan, threadsan, and memorysan.

[calm pawn]

whats sanitzer

[tulip summit]

This post should explain what it is

[calm pawn]

do i need to install it?

[tulip summit]

Should be with gcc on linux

[calm pawn]

im on mac

is that an issue

[tulip summit]

Should still work? Not sure

Just try adding -fsanitize=address to your compile flags

[calm pawn]

do i run it like gdb?

[tulip summit]

Once you compile it, just run the program like normal. When you hit the segfault, address sanitizer will emit all the debug info

[calm pawn]

oh okok

i just tried it doesnt work

like that right?

[tulip summit]

Yeah, that should be all you need. Mac must not have native support for it

[calm pawn]

ye and i tried running it on lunix then got a binary error

[robust ibex]

what?

Can you share the full error message?

[calm pawn]

ye i can

one moment

[tulip summit]

You're probably trying to run the binary built for mac, so it doesn't know what to do

[calm pawn]

ye is there a way to fix it

[tulip summit]

Are you passing -fsanitize=address to the command that links all the object files as well?

[calm pawn]

i havent yet

[tulip summit]

Ah, yeah. Try adding $(CFLAGS) to the end of your link command

[calm pawn]

this isssue is still happening

[tulip summit]

Run your clean target and rebuild

[calm pawn]

oh ye now it runs then seg fault hits

[tulip summit]

Yep. If you skim through the error you should see a summary line, which will tell you the file and line the segfault occurred on

[calm pawn]

i got the gdb

[tulip summit]

Ah, you did it through gdb. That's fine as well

First thing I'd check is your indices there

[calm pawn]

oh ok is it saying that the $ is out of bounds

or something

[robust ibex]

What is grid?

I.e. what datatype is it?

[tulip summit]

It's likely that you're indexing out of the bounds of grid, so check the values you're indexing it by

[robust ibex]

Cause I think you want to do grid[newX][newX] == '$' instead of ... == "$"

[calm pawn]

char ** grid

[robust ibex]

Also I'm not too sure if [newX][newX] is what you want rather than [newX][newY] or smth like that

[robust ibex]

Yeah, then you need to do ... == '$'

Otherwise you're comparing a char against a char *

Which obviously doesn't work

[tulip summit]

Didn't spot the double quotes lol. I was focusing on the segfault. Your screenshot shows you're compiling with warnings. Don't ignore those

[calm pawn]

this one sorry

[robust ibex]

You want to compare against a character (i.e. char), not against a string (i.e. char *)

[robust ibex]

Well, rn you're using the same variable/value for both indices.
This may be correct, but could also be incorrect, but depends on what you want to do

[calm pawn]

oh have u guys made a snake game before

[robust ibex]

nope

[tulip summit]

No, but usually you index a grid by an x and y, not x and x

Depends on what you're doing of course. This is just guessing lol

[calm pawn]

oh wait just understtod what u said lmao

[robust ibex]

But I did once download a snake game, fully written in pure native Windows batch 🐒

[calm pawn]

ye NewX and NewY

oh thanks ill look into it

and see how it works

[terse sparrow]

@calm pawn

Please Do Not Delete Posts!

Please don't delete forum posts. They can be helpful to refer to later and other members can learn from them. In the future you can use !solved to close a post and mark a post as solved.

[calm pawn]

!solve