The document discusses source-to-source compilers. It defines a source-to-source compiler as a compiler that takes source code as input and produces source code as output, which can then be used as input for another compiler. Some key differences between regular compilers and source-to-source compilers are discussed. Examples of popular source-to-source compilers like ROSE, DMS, OpenMP, and Cetus are provided.

1. Topic: SOURCE TO SOURCE COMPILER
Course Title: SYSTEM SOFTWARE
Course Code: CAP 607
SUBMITTED TO: SUBMITTED BY:
Mr. SANJAY SOOD MINTOO
JAKHMOLA
REG. NO.: 11009054
ROLL NO.: B20
SECTION: D1006

2. INTRODUCTION
A compiler, in the broadest sense, is just a tool that converts from a language (or a
way of expressing some knowledge) into another. Most people see compilers as
tools that have source code as input and produce binary files as output.
Source-to-source compilers have as input source code and produce source code as
output. It is assumed that the output can be used as well as the input of another
compiler (or even the same!).
It is also known as transcompiler (or transpiler) and it is also a type of compiler
that takes the source code of a programming language as its input and outputs the
source code in another programming language. For example, it may perform a
translation of a program from Pascal to C.
DEFINITION "transpiler":
A program which reads code in language A and converts it into code for language
B. The transpiler converts between languages at the same level. Examples: (C++
-> C, Pascal -> C).

3. DIFFERENCE BETWEEN COMPILER
AND TRANSCOMPILER
A compiler translates source code to machine code that can be understood by the
CPU hardware. A transpiler translates source code to another form of source code
that can be understood by another compiler.
Or
The difference between a compiler and a transpiler is that the compiler usually
converts from a high to a low level language (C -> Assembler, Java -> Bytecode)
while the transpiler converts between languages at (roughly) the same level.
Examples: (C++ -> C, Pascal -> C).
SOURCE MACHINE
COMPILER
CODE CODE
COMPILER WORKING

4. SOURCE SOURCE
TRANSPILER
CODE CODE
TRANSPILER WORKING
Why A Source-To-Source Compiler Is
Useful
One might wonder why a source-to-source compiler is useful if they are
generating again source code and not a binary ready to run like a "full" compiler
would.
Well, it turns that compilers are complex tools. Complex tools because they have
to deal with several processes including, but not limiting to: parsing the input,
checking the semantics, implement these semantics, finding out opportunities of
optimization under the semantics, generating binary code, etc.
So, that is why the source-to-source compiler is useful. A source-to-source
compiler performs a parsing phase but the generated AST must be much more

5. detailed than the one of a binary generating compiler. The reason is that the output
of the source-to-source compiler must be valid as an input for another compiler.
SOURCE-TO-SOURCE COMPILER
EXAMPLE
1. ROSE: It is an open source compiler infrastructure to build source-to-
source program transformation and analysis tools for large-scale Fortran
77/95/2003, C, C++, OpenMP, and UPC applications.
2. DMS Software Reengineering Toolkit: It is a source-to-source
program transformation tool. It can be used for translating from one
computer language to another, for compiling domain-specific languages to a
general purpose language, or for carrying out optimizations or massive
modifications within a specific language.
3. OpenMP: In this implementation is source-to-source, meaning that it
converts the input program, in Fortran source, which contains OpenMP
directives into an output program, also in Fortran source. The output
program explicitly creates and synchronizes parallel threads to implement
parallelism, as indicated by the OpenMP directives in the input program.
4. Cetus: It is a compiler infrastructure for the source-to-source
transformation of software programs. It currently supports ANSI C. Since
its creation in 2004, it has grown to over 80,000 lines of Java code, has been
made available publicly on the web, and has become a basis for several
research projects.