Re: C++ name mangling, old and new versions?

[Andi Kleen <ak at muc dot de>]

"T. Huld" <thomas.huld@jrc.it> writes:

> Hello,
> 
> It's probably just me doing something stupid, but here goes:
> 
> My setup: 
> 	Intel 586, Linux Red Hat 5.0, glibc-2.0.6, egcs-1.0.1
> 	all binary distributions.
> 
> 
> According to the info, egcs performs a name mangling which is not
> compatible with the one done by gcc-2.7. I have verified this by trying
> to link egcs-compiled programs with a binary distribution of the
> QT library. With the binary distribution library the linking fails, if I
> recompile the library with egcs the linking works OK.
> 
> HOWEVER, there is supposed to be an option: -fname-mangling-version-N, 
> where you can choose between the old name mangling convention (N=0)
> and the new one (N=1). But when I try to compile with the two different
> options, I get identical object files, and 'nm' reports no difference
> whatsoever. 
> 
> The call to g++ looks like this:
> 
> g++  -c   -fname-mangling-version-0 -g2  -Wall -DLINUX 
> -I/usr/home2/thomas/newreac/includes  -I/usr/local/qt/include 
> /usr/home2/thomas/newreac/sources/gui/gwndmain.cpp -o 
> /usr/home2/thomas/newreac/sources/gui/gwndmain.o

I had good look with -fno-rtti -fno-exceptions together with a 2.7.2
compiled Qt. The vtable layout is different when RTTI is enabled, so
egcs protects against mistakes by encoding that in the mangled name.
You have to explicitely turn it off, -fname-mangling-version-0 is not
enough.

-Andi