Re: gnulib's obstack_* symbols in dynamic exports on glibc. Intentional?
On Fri, 30 Dec 2022 19:26:48 +0100 Bruno Haible wrote: > Sergei Trofimovich wrote: > > to my surprise it did have one a set of dynamically exported symbols: > > > > $ nm -D `which ls` | grep -v '^ ' > > 004c0d40 T _obstack_allocated_p > > 00534808 D obstack_alloc_failed_handler > > 004c0bd0 T _obstack_begin > > 004c0bf0 T _obstack_begin_1 > > 004c0d80 T _obstack_free > > 004c0e00 T _obstack_memory_used > > 004c0c10 T _obstack_newchunk > > There's already a discussion on this topic, that started at > https://lists.gnu.org/archive/html/bug-gnulib/2022-12/msg7.html Aha, thank you! -- Sergei
Re: gnulib's obstack_* symbols in dynamic exports on glibc. Intentional?
Sergei Trofimovich wrote: > to my surprise it did have one a set of dynamically exported symbols: > > $ nm -D `which ls` | grep -v '^ ' > 004c0d40 T _obstack_allocated_p > 00534808 D obstack_alloc_failed_handler > 004c0bd0 T _obstack_begin > 004c0bf0 T _obstack_begin_1 > 004c0d80 T _obstack_free > 004c0e00 T _obstack_memory_used > 004c0c10 T _obstack_newchunk There's already a discussion on this topic, that started at https://lists.gnu.org/archive/html/bug-gnulib/2022-12/msg7.html Bruno
gnulib's obstack_* symbols in dynamic exports on glibc. Intentional?
Hello bug-gnulib (and libc-alpha, CCed)! The other day I was looking at simplest programs to make sure they don't normally have dynamic exports. I picked coreutils-9.1 'ls'. And to my surprise it did have one a set of dynamically exported symbols: $ nm -D `which ls` | grep -v '^ ' 004c0d40 T _obstack_allocated_p 00534808 D obstack_alloc_failed_handler 004c0bd0 T _obstack_begin 004c0bf0 T _obstack_begin_1 004c0d80 T _obstack_free 004c0e00 T _obstack_memory_used 004c0c10 T _obstack_newchunk That was a surprise to me. I think they are exported because gnulib defines them in obstack.c. AFAIU gnulib assumes that local implementation is better that glibc's as it supports 64-bit object sizes. I think ld decides to put symbols into dynamic exports to make sure local symbols intended to override glibc's need to propagate to glibc and other libraries that might use it. Questions: 1. Is it a safe override to mangle symbols ilke that? Or would glibc's versioned symbols be used just fine by existing libraries? $ nm -D /lib/libc.so.6 | fgrep obstack 00201338 B _obstack@GLIBC_2.2.5 0009aa70 T _obstack_allocated_p@@GLIBC_2.2.5 001fb338 D obstack_alloc_failed_handler@@GLIBC_2.2.5 0009a780 T _obstack_begin@@GLIBC_2.2.5 0009a840 T _obstack_begin_1@@GLIBC_2.2.5 001fa208 D obstack_exit_failure@@GLIBC_2.2.5 0009aab0 T _obstack_free@@GLIBC_2.2.5 0009aab0 T obstack_free@@GLIBC_2.2.5 0009ab40 T _obstack_memory_used@@GLIBC_2.2.5 0009a900 T _obstack_newchunk@@GLIBC_2.2.5 0007e110 W obstack_printf@@GLIBC_2.2.5 0011e9c0 T __obstack_printf_chk@@GLIBC_2.8 0007e100 W obstack_vprintf@@GLIBC_2.2.5 0011ea80 T __obstack_vprintf_chk@@GLIBC_2.8 2. Would it be feasible to avoid dynamic symbol export and maybe rename gnulib's symbols to avoid clash with glibc? I would expect loading to be a tiny bit faster for binaries without dynamic exports like that. Thanks! -- Sergei