TM4C123GH6PM / TM4C123GH6PGE microcontroller maximum C system stack size

The system stack uses the internal static RAM of the device. The TM4C123GH6PM has 32KB of internal static RAM. You cannot use all of that for stack space because your application will also need some space for static variables and possibly heap space. Look at the .map file created by your project to see how much of the RAM was used for static variables or heap. The rest can be used for the stack.

Besides changing the code composer option you pictured above, you need to edit the link command file used to actually increase the stack size.  Here is a line from the link command file of the "Hello" example using a stack size of 512 bytes:

__STACK_TOP = __stack + 512;

In general yes, you can set the stack size to 1024 or 2048. However, as I tried to explain in the earlier post, it depends on how much of the internal RAM you use for static variables and heap. I suggest you look at the .map file generated to see how much RAM you are currently using. Unless your project is quite large, or using very large arrays of data, you are likely to have no problem setting your stack size to 2048 bytes.