Re: [Bug-readline] [PATCH] Enable visibility annotations

[Yury Gribov]

On 04/14/2016 05:07 PM, Pedro Alves wrote:
> On 04/14/2016 01:28 PM, Yury Gribov wrote:
>
> > Thanks, this sounds as a general problem with visibility enabling.  Is
> > there some (relatively straightforward) way to find all used symbols?
> > I'm afraid there'll be more than just _rl_*...
>
> I don't know of one, other than a mass rebuild (which is something
> that I have never done myself).
>
> A cheap proxy may be to look under /usr/bin /usr/lib etc. for
> binaries with DTNEEDED readline, and then compare all of readline's
> extern symbols with the binary binaries' set of extern symbols,
> check for overlap in symbols that are not prefixed "rl_".

Good idea, here are results for my Ubuntu 14 (I simply look for any 
symbol intersections):

# Find all imported symbols in rootfs
for f in $(find /bin /sbin /usr/bin /usr/sbin /usr/lib* /lib*); do if 
file $f | grep -q ELF; then readelf -sDW $f | awk '/UND/{print $9}'; fi 
; done > all_undefs.lst
sort -u all_undefs.lst > all_undefs_sorted.lst

# Find symbols exported by original readline
readelf -sDW ~/install/readline/lib/libhistory.so | awk '!/UND/{print 
$9}' > rl_orig.lst
readelf -sDW ~/install/readline/lib/libreadline.so | awk '!/UND/{print 
$9}' >> rl_orig.lst
sort -u rl_orig.lst > rl_orig_sorted.lst

# Find symbols exported by new readline
readelf -sDW ~/install/readline-patched/lib/libhistory.so | awk 
'!/UND/{print $9}' > rl_new.lst
readelf -sDW ~/install/readline-patched/lib/libreadline.so | awk 
'!/UND/{print $9}' >> rl_new.lst
sort -u rl_new.lst > rl_new_sorted.lst

# Symbols from old readline which may be used somewhere
$ comm -12 all_undefs_sorted.lst rl_orig_sorted.lst
_rl_qsort_string_compare
xmalloc

# Symbols from new readline which may be used somewhere
$ comm -12 all_undefs_sorted.lst rl_new_sorted.lst
_rl_qsort_string_compare

Whoever needs xmalloc should not link to libreadline :)

-Y