1. COP4620 – Programming Language Translators Dr. Manuel E. Bermudez
Bootstrappping
COP4620 – Programming Language Translators Dr. Manuel E. Bermudez

2. Bootstrapping Definition Example: A Compiler for C Cross-compiling
Topics
Bootstrapping Definition
Example: A Compiler for C
Cross-compiling

3. Bootstrapping
The notion of implementing a language, by means of using (part of) that language’s own implementation.
Notation: T-diagram
Source
Target
Language
Written in

4. T-diagrams C M
APPLICATION
Source Coincides
Object Coincides
Execution

5. Bootstrapping
Example: We wish to have a C compiler for a new processor, M.
How do we get it ?
Possibility #1: Write the compiler directly by hand, in machine language? In assembly language ?  C M

6. Bootstrapping
Possibility # 2: Write the C compiler in some other language L,
that is already implemented on M. Then, compile the compiler.
But, ... this is probably still too much work. L M
C M
C M
L Compiler

7. Bootstrapping Possibility # 3: T M First, implement T, a subset of C.
Now, T is implemented.
Then, write the
desired compiler in T,
and compile it. L M
T M T M
C M

8. Bootstrapping
If T is choosen well, the T  M compiler and the C  M compiler (in T) together, are easier to write than the C  M (in L) compiler.
Theoretically, this process can go on indefinitely, bootstrapping up the level of the language.
In practice, however, new constructs interfere with each other (and with old ones), until further bootstrapping becomes ummanageable.

9. Bootstrapping
Now, lets suppose we wish to port C to a new machine, M’.
Possibility #1: Same as for M.
Possibility #2: Same as for M.
Possibility #3: Same as for M.

10. Bootstrapping Possibility # 4: T M’ Step 1: Same as for M
(implement T on M’).
Step 2: Modify the C M
compiler, to generate
code for M’.
Then, compile the
compiler. L M’
T M’ T M’
C M’

11. Bootstrapping Possibility # 5 C M’ (cross-compiling):
Don’t use T ! Instead, use
implementation of C on M.
Step 1:
Step 2: Compile the
compiler (on M). C M
C M’
Cross-compiler C M’ M
C M’

12. Bootstrapping Definition Example: A Compiler for C Cross-compiling
summary
Bootstrapping Definition
Example: A Compiler for C
Cross-compiling