[BUG] error in global variables strong aliasing

[Peter S. Mazinger]

On Sat, 18 Mar 2006, Amir Shalem wrote:

> hey,
> 
> 
> after commit http://www.uclibc.org/lists/uclibc-cvs/2006-March/009686.html
> 
> global variables such as environ, errno, and friends are broken
> 
> when compiling against uclibc dynamiclly only.

maybe

for _errno, that shouldn't be even exported, but is used by linuxthreads, 

> 
> 
> you can check it out using:
> 
> 
> /* errno and _errno are strongly aliased */
> 
> extern int errno;
 ^^^
man page says: don't do that, it will not work with modern versions of the 
C library (this is probably true for uClibc if we will get TLS working)

> 
> extern int _errno;
> 
> 
> int main(void)
> 
> {
>     errno = 0;
> 
>     _errno = 1;
> 
>     printf("errno: %d _errno: %d\n", errno, _errno);
> 
>     return 0;
> 
> }
> 
> 
> if you compile this program staticlly you will see same result (=1) in 
> both variables,
> 
> but if you compile this program dynamiclly you will see diffrent results.

I have the same result (=1) dynamically (x86 native)

> 
> 
> same happens with __environ & environ.

this one is curious, I had a bug report before yours when I made use of 
hidden global data (what this svn commit undid due to stability problems)

> 
> if changing to weak_alias (instead of strong_alias) it works again.

on which arch?

> 
> 
> you can simulate this bug by creating a library from:
> 
>          int var = 0;
> 
>          extern int var2 __attribute__ ((alias ("var")));
> 
> 
> and then play with 'var' and 'var2'.
> 
> 
> I have manage to reproduce it with gcc 3.4.4 + binutils 2.15 + FreeBSD 6.1,

what does FreeBSD mean here, your host OS? have you used buildroot?
> 
> and using gcc 4.1.0 + binutils 2.16.1 + uClibc 20060317

how can this be compared to the above, is this native?
> 
> 
> Amir.

thanks, Peter

-- 
Peter S. Mazinger <ps dot m at gmx dot net>           ID: 0xA5F059F2
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