Re: [Tinycc-devel] Nested functions

[Zdenek Pavlas]

Anton wrote:
> Have been lookng over this  great  discussion  about  nested
> functions and now I am interested: What  are  the  arguments
> agains nested procedures/functions, except the  difficulties
> in implementation and speed issues?
1. Portability issues.  Your code now requires compliant compiler and 
runtime.

2. Security.  There was a strong rationale to make stack not 
executable.  Nested functions make it even worse than before: not only 
is stack executable, but if there is a buffer overflow when the nested 
function is in scope, the attacker knows that a fixed `esp + const` is 
getting to be called, and very easily exploit that.

Speed is not an issue.  The GCC implementation is pretty fast.  Actually 
I think it's a well designed feature.  Very intuitive and sometimes 
usefull.  But IMHO just not worth the pain.

PS: Why didn't they came a bit farther in syntax, allowing anonymous 
local functions and turning them to function pointers.  That sould be 
easy.  Think of:

void for_each(struct list *head, void (*callback)(struct item *item));
struct list *h;
..
for_each(h, void(struct item *i) { printf("item %p\n", i); });

or even better, ala Ruby:

for_each(h) void(struct item *i) {
 printf("item %p\n", i);
}

--
Zdenek Pavlas