Microchip Technology XC8 Standard Compiler (Workstation) SW006021-1 SW006021-1 User Manual

®

 2012 Microchip Technology Inc.

DS52053B-page 131

MPLAB XC8 C Compiler supports a number of special features and extensions to the 
C language which are designed to ease the task of producing ROM-based applications 
for 8-bit PIC devices. This chapter documents the special language features which are 
specific to these devices.

• ANSI C Standard Issues

• Device-Related Features

• Supported Data Types and Variables

• Memory Allocation and Access

• Operators and Statements

• Register Usage

• Functions

• Interrupts

• Main, Runtime Startup and Reset

• Library Routines

• Mixing C and Assembly Code

• Optimizations

• Preprocessing

• Linking Programs

This compiler conforms to the ISO/IEC 9899:1990 Standard for programming lan-
guages. This is commonly called the C90 Standard. It is referred to as the ANSI C 
Standard in this manual.

Some violations to the ANSI C Standard are indicated below in 
Section 5.2.1 “Divergence from the ANSI C Standard”. Some features from the 
later standard C99 are also supported.

The C language implemented on MPLAB XC8 C Compiler diverges from the ANSI C 
Standard in one area: function recursion. Due to limited memory and no hardware 
implementation of a data stack, recursion is not supported and functions are not 
reentrant.

The compiler can make functions called from main-line and interrupt code appear to be 
reentrant via a duplication feature. See Section 5.9.5 “Function Duplication”.

Certain features of the ANSI C standard have implementation-defined behavior. This 
means that the exact behavior of some C code can vary from compiler to compiler. The 
exact behavior of the compiler is detailed throughout this manual, and is fully 
summarized in Appendix C. “Implementation-Defined Behavior”.