Re: g++ and -nostdlib

[Richard PALO]

Le 08/11/13 20:07, Charles Wilson a écrit :
> On 11/8/2013 1:49 PM, Bob Friesenhahn wrote:
> > Isn't it because libtool wants to control the order of the linking and
> > assure that all dependencies (including static) are tracked/known and
> > applied at the correct times?  It wants to assure that static
> > dependencies are linked into the dependent program rather than into some
> > dependent shared library (and thus causing a problem).
> >
> > It was common (and perhaps still is) for the GNU C++ library to be
> > delivered as a static library for Windows/MinGW because C++ exceptions
> > were not handled properly when thrown by DLLs.
> >
> > Quite a lot of effort went into making this work the way it currently
> > does.
> >
> > First libtool tries to take away all of the libraries which would be
> > added automatically and then it applies the libraries that GCC says it
> > would use at the correct time.
>
> One of my wishlist roundtuit items is to special-case this behavior for
> libtool + GNU toolchains.  For that combo, instead of the procedure Bob
> outlines, and then using $LD to link....just use the compiler driver
> (e.g. g++, or gfortran, or gcc) to link, WITHOUT -nostdlib [1].  We're
> already passing the ABI-modifying -m and -f flags anyway, and it would
> really REALLY simplify libtool's logic...
>
> [1] unless of course the end user put -nostdlib in $LDFLAGS or something.
>
> --
> Chuck
I believe Chuck is oriented in the right direction.

A good example is with -fstack-protector.

gcc/g++ knows how to link depending upon whether the platforms libc has 
SSP support or not.

I doubt very much that libtool wants to figure out whether to add the 
specific libraries necessary for SSP to the link command.
It *should* however pass through the provided flags to the compiler 
driver, and not strip in this case '-fstack-protector'; object of:
> Bug: linking shared libraries on Cygwin results in undefined  references to 
> __stack_chck_guard for code compiled with -fstack-protector

In this particular "worst" case, '-fstack-protector' is stripped, and 
even if it passed through, the g++ '-nostdlib' defeats the purpose!