[pushed] c++: Make references to __cxa_pure_virtual weak.

[Andreas Schwab]

On Mai 11 2020, Jason Merrill via Gcc-patches wrote:

> If a program has no other dependencies on libstdc++, we shouldn't require it
> just for __cxa_pure_virtual, which is only there to give a prettier
> diagnostic before crashing the program; resolving the reference to NULL will
> also crash, just without the diagnostic.

That doesn't work on ia64:

pure-virtual1.o:(.data.rel.ro._ZTV1A[_ZTV1A]+0x10): undefined reference to `__cxa_pure_virtual'
collect2: error: ld returned 1 exit status
$ nm -u pure-virtual1.o 
                 U __cxa_pure_virtual

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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