system call

jaysrikrishna · 12-16-2007, 12:33 AM

I didn't found any answer for the relationship between
sigsetjmp(env),siglongjmp(env,2),setjmp(env) and longjmp(env,1) ,
can any one answer me this in context that how they related with each other with respect to variable env .

KrahnacK · 12-16-2007, 03:50 AM

i took a look at : http://man.he.net/man3/setjmp

it says :

Code:

       setjmp() saves the stack context/environment in
       env for later use by longjmp().  The stack context will be
       invalidated if the function which called setjmp() returns.

       If  you  want  to  save   signal   masks,   use
       sigsetjmp(3).

i'm just curious about why do people actually need these instead of calling a new function ?

btmiller · 12-16-2007, 04:28 PM

People use them because they can provide a sort of exception handling that let's you unroll the function call stack back to a predetermined point in the event of some sort of error. This can be used to implement a sort of try ... catch semantic in C. However, it makes the program quite unreadable and definitely lives in the land of guru-level C tricks,

KrahnacK · 12-16-2007, 05:12 PM

all right, i think i get the point (i didn't seen it that way)

thanks for enlightening me

jlliagre · 12-17-2007, 01:45 AM

And, by the way, these functions aren't system calls.