function

[St0rM-MaN]

hi all
defining functions inside of main like this

main()
{

       int function()
        {
                 int x=5;
                return x;
        }



        printf("%d %d \n",function(),test());
}

it will be only local to main right?
and my question is :
is there is any thing wrong with that code i mean
can it cause any kind of problesm or Undefined behaviour?
thanks in advance

[Salem]

It's non-standard C.
Any compiler in ANSI mode will just throw it out.

[MacGyver]

Slightly modified version of the compiler output when I compile:

stupidcode.c:2: warning: return type defaults to `int'
stupidcode.c: In function `main':
stupidcode.c:5: warning: ISO C forbids nested functions
stupidcode.c:12: warning: implicit declaration of function `printf'
stupidcode.c:12: warning: implicit declaration of function `test'
stupidcode.c:13: warning: control reaches end of non-void function
(.text+0x29):stupidcode.c: undefined reference to `test'
collect2: ld returned 1 exit status

See anything that jumps out at you?

[St0rM-MaN]

i am just using
gcc fu.c -o fu
and it works with me
does this mean that gcc is not compiling it in ansi mode?

[St0rM-MaN]

It is unusual for a block-structured language to prohibit you from defining functions inside other functions, but this is one of the characteristics of C. Although it isn't obvious, this helps to improve the run-time performance of C by reducing the housekeeping associated with function calls.

i got this from the c book
but i just can't understand why did gcc compiled it

[MacGyver]

Try the -ansi and -pedantic switches.

[St0rM-MaN]

gcc -Wall -ansi function.c -o function
function.c: In function `test':
function.c:6: warning: implicit declaration of function `function'
function.c: At top level:
function.c:12: warning: return type defaults to `int'
function.c: In function `main':
function.c:19: warning: control reaches end of non-void function

wall and ansi options gives my me errors
thanks

[St0rM-MaN]

-Wall
tells the compiler to implement 'all' Warning options. Warnings are diagnostic messages that report constructions which are not inherently erroneous but which are risky or suggest there may have been an error

i got it now
sorry for my stupid question but i have to ask