about libc function interfaces and ld --wrap

[Daniel Jacobowitz]

On Fri, Mar 03, 2006 at 10:24:48PM +0000, sean yang wrote:
> Several question to ask about libc and linker:
> 
> (1) I would ask general glibc design question: whether an exported function 
> in glibc can be called by another function internally?
> For example (--which is a faked example),
> malloc is an exported function;
> foo(this is a faked name example)  is another exported function;
> ** is it possible that foo( ) calls malloc( )  internally?

Yes.

> (2) If the answer to above question is yes, then the following that 
> question is: if I have printf wrapped by my own layer (by "ld --wrap 
> printf"), will _wrap_malloc() change the internal call's behavior?
> 
> void *
> __wrap_ malloc(int c)
> {
>  printf ("Coming here\n", c);
>  return __real_malloc (c);
> }

Not necessarily.

> (3) If there a convenient way to wrap multi function, e.g., malloc, printf, 
> getc...., with same "added functionality" (say just print "coming here"). I 
> mean an better way than create each wrapper seperately?

Nope.

-- 
Daniel Jacobowitz
CodeSourcery