Re: Question regarding __clock_gettime symbol visibility across glibc build

[Lukasz Majewski <lukma@denx.de>]

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Hi Joseph,

> On Sat, 21 Mar 2020, Lukasz Majewski wrote:
> 
> > > /work/lukma/glibc/glibc-many-build/src/glibc/malloc/memusage.c:181:
> > > undefined reference to `__clock_gettime64'  
> 
> I.e. __clock_gettime64 is not exported at any symbol version in the 
> dynamic symbol table of libc.so.
> 
> Any symbol defined in libc.so and used in another glibc shared
> library or executable needs to be exported at some symbol version in
> some Versions file.  In the case of symbols for 64-bit time, it
> should be exported at version GLIBC_PRIVATE until we're ready to
> support _TIME_BITS=64 in the headers, at which point all such symbols
> should be exported at the version of the next glibc release and be
> removed from GLIBC_PRIVATE if there.

And the penny has dropped. The __clock_gettime64 indeed is not exported
in the current glibc. It is exported with my patches for Y2038 support.

I will export __clock_gettime64 in this patch series. Big thanks for the
explanation.

> 
> > > nm
> > > ./work/glibc/glibc-many-build/build/glibcs/arm-linux-gnueabi/glibc/libc.so
> > > | grep clock_gettime  
> 
> nm uses the static symbol table by default.  You need nm -D, objdump
> -T (shows symbol versions as well) or readelf --dyn-syms to look at
> the dynamic symbol table.
> 



Best regards,

Lukasz Majewski

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