Languages & Compilers From source code to executable code

#define L 10

main() { int i,k,r[L]; for(i=0;i<L;i++) { k = 3*i+2; r[i] = k*k; } }

0010011000110001 1000111011001010 1101010010101001 1010101010101111 1010100111111111 0101010101010101

Compiler

Error Messages

The compiler

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2

Source and object languages

•  There are... hundreds of programming languages ▫  General purpose programming languages

  C, C++, Pascal, Fortran, Java, Basic, Lisp, Prolog, perl.... ▫  Special purpose languages

  Text formatting (Tex, Latex...)   Database management and querying (SQL)

•  The compiler translates the source language into ▫  Another high-level programming language ▫  e.g. pascal -> C ▫  The machine code for a given processor/architecture

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Parsing and generation

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X = A+B*C X *

+ =

C B A

The compiler “context”

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preprocessor

assembler

linker/loader

Source code skeleton

source program

assembly code

object code

executable code

libreries

include, define (macro)

Compiler structure

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6

lexical analysis

syntactic analysis

semantical analysis

intermediate code generation

optimization

object code generation

error handling symbol table

Lexical analysi (scanning)

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7

int somma, diff = 0.3;

Syntatic Analyis (parsing)

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8

assignment statement

identifier expression

expression

expression identifier

identifier number

expression

expression A

=

+

*

B C 60

Syntatic rules

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9

base rules

recursive rules

Sematical analysis •  Yields the sematics associated to the syntatic structure ▫  It verifies that the usage rules of the language are satisfied

  identifier declarations (e.g. duplicate definitions,...)   type check (compatibility of types in expressions, automatic

type conversion, type check for vector indexes, ecc..)

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10

*

C

D

int D; float C;

type conversion function int -> float

Symbol table •  It memorizes the identifiers and their associated attributes ▫  memory allocation ▫  type ▫  visibility scope ▫  number and type of function/procedure arguments

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11

memory allocation

Object code generation

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12

= id1

id2 id3

+ * int-to-float

60

t1 = int-to-float(60) t2 = id3 * t1 t3 = id2 + t2 id1 = t3

t1 = id3 * 60.0 id1 = id2 + t1

MOVF id3, R2 MULF #60.0, R2 .............

internal intermediate representation

intermediate code generation

code optimization

object code generation