libsys.so.7 for armv7 (at least) has "NOTYPE GLOBAL DEFAULT UND __aeabi_unwind_cpp_pr0" but aarch64 and amd64 do not?

This note is related to:

<https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=292567>

(__aeabi_unwind_cpp_pr1 has a similar status.)

It is not clear to me if other non-tier-1 architectures might have
something similar at issue, now or in the future.


Is the following expected? Appropriate?

In an armv7 context (watch for possible line wraps):

# readelf --dyn-syms /lib/libsys.so.7 | grep _cpp_
     2: 00000000     0 NOTYPE  GLOBAL DEFAULT   UND __aeabi_unwind_cpp_pr0
     3: 00000000     0 NOTYPE  GLOBAL DEFAULT   UND __aeabi_unwind_cpp_pr1

In more detail:

# readelf --dyn-syms /lib/libsys.so.7

Symbol table '.dynsym' contains 1211 entries:
   Num:    Value  Size Type    Bind   Vis       Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT   UND
     1: 00000000     0 NOTYPE  WEAK   DEFAULT   UND __cxa_finalize
     2: 00000000     0 NOTYPE  GLOBAL DEFAULT   UND __aeabi_unwind_cpp_pr0
     3: 00000000     0 NOTYPE  GLOBAL DEFAULT   UND __aeabi_unwind_cpp_pr1
. . .

on aarch64:

# readelf --dyn-syms /lib/libsys.so.7 | grep _cpp_
#

on amd64:

# readelf --dyn-syms /lib/libsys.so.7 | grep _cpp_
#

For armv7 at least, it contributes to the likes of (not specific to
gcc15 for similar results):

# gcc15 -static-libgcc main.c

producing messages like:

/usr/local/bin/ld: a.out: hidden symbol `__aeabi_unwind_cpp_pr0' in
/usr/local/lib/gcc15/gcc/armv7-portbld-freebsd16.0/15.2.0/libgcc_eh.a(unwind-arm.o)
is referenced by DSO
/usr/local/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status

In fact:

# gcc15 -static-libgcc -fno-exceptions main.c

also produces:

/usr/local/bin/ld: a.out: hidden symbol `__aeabi_unwind_cpp_pr0' in
/usr/local/lib/gcc15/gcc/armv7-portbld-freebsd16.0/15.2.0/libgcc_eh.a(unwind-arm.o)
is referenced by DSO
/usr/local/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status

Despite the very simple C context.

In an armv7 14.3-STABLE context (so predating a
libsys.so.7 existing to be involved with libc.so.7 use):

# llvm-readelf --dyn-syms /lib/libc.so.7 | grep _cpp_
#

So in 14.* there is no such __aeabi_unwind_cpp_pr0 reference involved
when linking against libc.so.7 . (Same for __aeabi_unwind_cpp_pr1 .)

Definitely only a FreeBSD 15+ issue for what contexts can run into the
issue.


A question here is if, at least for armv7, all use of -static-libgcc for
FreeBSD 15+ needs to supply a usable/linkable pair:

__aeabi_unwind_cpp_pr0
__aeabi_unwind_cpp_pr1

even if -fno-exceptions is also in use.


-- 
===
Mark Millard
marklmi at yahoo.com