[Buildroot] Exception support

[Buildroot] Exception support

[Thomas Moschny]

Hi,

is there a way to get a toolchain built for i686, that supports C++ 
exceptions?

In a buildroot naively build using gcc 4.1.0 or 4.1.1 and uclibc 0.9.28, C++ 
exceptions don't work. Apps instead abort with "terminate called after 
throwing an instance of foo" when an exception of type foo is thrown.

I found this thread: 
http://www.nabble.com/gcc-4.1.1-and-exception-handling-(libstdc++)-t2084671.html
but the quintessence remains unclear to me.

Thanks,
Thomas

[Buildroot] Exception support

[Ed Swierk]

On 8/28/06, Thomas Moschny <thomas.moschny@gmx.de> wrote:
> is there a way to get a toolchain built for i686, that supports C++
> exceptions?
>
> In a buildroot naively build using gcc 4.1.0 or 4.1.1 and uclibc 0.9.28, C++
> exceptions don't work. Apps instead abort with "terminate called after
> throwing an instance of foo" when an exception of type foo is thrown.

I've got C++ exceptions working with gcc 4.1.1 by enabling
BR2_GCC_USE_SJLJ_EXCEPTIONS in my buildroot configuration, and
changing --disable-__cxa_atexit to --enable-__cxa_atexit in
gcc-uclibc-3.x.mk. The former forces gcc to implement exceptions with
setjmp/longjmp rather than the more efficient stack unwinding, while
the latter enables code ensuring that static objects are cleaned up
properly on exit.

Apparently it is even possible to get stack unwinding to work, but I
have not tried it myself. See the thread beginning at
http://uclibc.org/lists/uclibc/2006-August/016090.html .

--Ed

[Buildroot] Exception support

[Thomas Moschny]

ON Thursday 31 August 2006 00:23 Ed Swierk wrote:
> On 8/28/06, Thomas Moschny <thomas.moschny@gmx.de> wrote:
> > is there a way to get a toolchain built for i686, that supports C++
> > exceptions?
>
> I've got C++ exceptions working with gcc 4.1.1 by enabling
> BR2_GCC_USE_SJLJ_EXCEPTIONS in my buildroot configuration,

This seems to work. Btw, it took me a while to find out what 'sjlj' stands 
for :)

> and changing --disable-__cxa_atexit to --enable-__cxa_atexit in
> gcc-uclibc-3.x.mk.

I tried setting --enable-__cxa_atexit as an extra gcc option, but got an 
undefined reference afterwards.

> Apparently it is even possible to get stack unwinding to work, but I
> have not tried it myself. See the thread beginning at
> http://uclibc.org/lists/uclibc/2006-August/016090.html .

I know this thread, but it is unclear to me how to force usage of stack 
unwinding. unwind-dw2-fde.o seems not to work (that's why I started this 
thread). Now, if I edit toolchain/gcc/4.1.1/100-uclibc-conf.patch to not 
change LIB2ADDEH, then unwind-dw2-fde-glibc.o is built (and would be used), 
but it contains an undefined reference to dl_iterate_phdr.

Thomas