Fix all malloc and other potential memory problem (work-in-process)

[xuchunyang]

• [x] Remove unnecessary casts of the return of malloc()
• [ ] Check and handle every return of malloc(), success or failure, life or death

[hit9]

It's necessary.

[xuchunyang]

It's necessary.

hmm, necessary for what exactly?

I am new to C programming and I plan to give up this pull request and create my own todo command line tool. Thank you for sharing the code.

[nutsi]

Check the return of malloc is a good practice but the manual says : man malloc(3) section NOTES

By default, Linux follows an optimistic memory allocation strategy. This means that when malloc() returns non-NULL there is no guarantee that the memory really is available.

But It's always a good idea to check if a pointer is valid before using it.

For the cast of malloc's return, I don't know the reason of that, you can read everything about that on internet.

[hit9]

Thanks @nutsi .