Re: Function redefined

[Eljay Love-Jensen <eljay at adobe dot com>]

Hi Amit,

>1. Doesn't gcc find the definition twice and shouldn't it report the error?

No.  Definitions in your object code supersede definitions in archive 
libraries and shared object libraries.

If not careful, antics and hilarity can ensue.

What I found was that it uses the first definition found.

>2. Was it always like this or sometime during the course of evolution of 
compilers, it was decided that the first definition would be used?

It's been like that as long as I'm aware.  But I've only been programming 
for 28 years.

Maybe in the good old days before I started programming it was 
different.  Or maybe it's different on platforms other than the ones I'm 
familiar with.

>3. Or, since it is compiled with dynamic library, it is behaving that way?

Yes, dynamic libraries (SSO) behave that way, although DSO's do not.

SSO - static shared object
DSO - dynamic shared object

You can list out your executable's SSO's using the ldd command.

DSO's explicitly use the dlopen and manually match symbols up from the 
shared object library.

You could use a DSO to access the atoi function in the library, even if you 
have an SSO or executable that has defined a different atoi function.

>4. Would compiling it with static C library (libc.a) would give me a 
"function redefined" error?

No.  Your object code supersedes both shared object libraries and archive 
libraries.

(There are tricks to make that not happen, but you'd have to take measures 
and fiddle with some of the compiler/linker options.)

HTH,
--Eljay