[Bug ld/26551] A definition referenced by an unneeded (--as-needed) shared object should be exported

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26551

--- Comment #8 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Fangrui Song from comment #7)
> 
> >a.c <<e cat
>  #include <dlfcn.h>
>  int foo() { return 42; }
>  int main() {
>    void *h = dlopen("./b.so", RTLD_LAZY);
>    int (*bar)(void) = dlsym(h, "bar");
>    return bar();
>  }
> e
> >b.c <<e cat
>  int foo();
>  int bar() { return foo(); }
> e
> 
> cc -fuse-ld=bfd -shared -fPIC b.c -ldl -o b.so
> cc -fuse-ld=bfd -pie -fPIE a.c -Wl,--push-state -Wl,--as-needed ./b.so
> -Wl,--pop-state -ldl
> 
> ./a.out => symbol lookup error: ./b.so: undefined symbol: foo
> 
> -fuse-ld=gold or -fuse-ld=lld is good.

If it is the only use case, why not use

'--dynamic-list=DYNAMIC-LIST-FILE'
     Specify the name of a dynamic list file to the linker.  This is
     typically used when creating shared libraries to specify a list of
     global symbols whose references shouldn't be bound to the
     definition within the shared library, or creating dynamically
     linked executables to specify a list of symbols which should be
     added to the symbol table in the executable.  This option is only
     meaningful on ELF platforms which support shared libraries.

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