About a new gcc feature. I hope you read this e-mail

["lucas75it at tiscali dot it" <lucas75it at tiscali dot it>]

First of all: excuse my english, it doesn't work very well !

Two years ago (2000) i studied myself the AST of the gcc.
I learnt its structure, macros, syntax, ... (if you want see 
www.unisannio.it/villano/students/masone/)
Now i'am reading your book: "GNU Compiler Collection Internals, for gcc 3.4"
I have a little idea.

We write the C file foo.c and we compile it.
The compiler make the passes:

1 - parsing
2 - tree optmization
3 - RTL generation
4 - Sibiling call optimization
5 - ................
6 - ................

After the first step (parsing) we have the AST of foo.c

Now, can we introduce a new substep that give us the ability of visit 
the AST ?
Follow me.

We can introduce a new flag; for example -vast (visit ast).
We can modify the gcc source code in this way: after parsing pass if 
vast is on we call a module that visit the AST.
In C we can write:


/* To inttroduce in a gcc source file.
  After parsing pass of gcc.
*/
if (flag_vast_is_ON) {

   init_ast_walker(....);
   
   launch_ast_walker(....);

   destroy_ast_walker(....);

}


We write a module walker.c that implement these functions. We place it 
in gcc/walkers/ directory.

Each programmer, student, researcher can write its own walker: a walker 
for analyze declarations,
a walker for analyze statements, and so on ...

"The gcc team write a compiler for the freedom, and in this way the team 
give other fredoom."

We can also modify the previous sequence of passes by introducing some 
others walkers. For example:

1 - parsing
   1.1  walk around AST
2 - tree optmization
   2.1  walk around Opt AST
3 - RTL generation
   3.1  walk around RTL
4 - Sibiling call optimization
5 - ................
6 - ................

What do you think about this ?

Gianluca Masone, ... maybe in the future i'll become a programmer !

Bye, bye.


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