The items below are required to compile code on the iPhone.
You need to install them only if they are not currently installed.
That is, you do not have to re-install them.
Please open Cydia on your iPhone; you need to be connected to a WiFi (or EDGE/UMTS) network. Declare yourself a Developer if asked. Follow any update steps that Cydia requires or suggests.

The compiler, assembler and linker are needed to produce code :-)
Cydia -> Sections -> Development -> GNU C Compiler
Cydia -> Sections -> Development -> C++ Standard Library

The Link Identity Editor is necessary to make code run on the iPhone.
It 'pseudo' signs the executable code.
Cydia -> Sections -> Development -> Link Identity Editor.

Click 'OK' when you are done, or 'Cancel' to stop the installation.