On 1/19/26 13:37, Mark Millard wrote:
> 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.
>
>
The examples of the aarch64 and amd64 grep usage that I copy/pasted into
my notes were poor, assuming naming conventions that need not be
assumed. Better was my test via (watch for potential line wrapping):
aarch64 main:
# readelf --dyn-syms /lib/libsys.so.7 | grep 'NOTYPE GLOBAL DEFAULT UN'
# readelf --dyn-syms /lib/libc.so.7 | grep 'NOTYPE GLOBAL DEFAULT UN'
1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND environ
2: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __progname
amd64 main:
# readelf --dyn-syms /lib/libsys.so.7 | grep 'NOTYPE GLOBAL DEFAULT UN'
# readelf --dyn-syms /lib/libc.so.7 | grep 'NOTYPE GLOBAL DEFAULT UN'
1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND environ
2: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __progname
Compared/contrasted with:
armv7 main:
# readelf --dyn-syms /lib/libsys.so.7 | grep 'NOTYPE GLOBAL DEFAULT UN'
2: 00000000 0 NOTYPE GLOBAL DEFAULT UND __aeabi_unwind_cpp_pr0
3: 00000000 0 NOTYPE GLOBAL DEFAULT UND __aeabi_unwind_cpp_pr1
# readelf --dyn-syms /lib/libc.so.7 | grep 'NOTYPE GLOBAL DEFAULT UN'
1: 00000000 0 NOTYPE GLOBAL DEFAULT UND environ
2: 00000000 0 NOTYPE GLOBAL DEFAULT UND __progname
And with:
armv7 14.3-STABLE:
# llvm-readelf --dyn-syms /lib/libc.so.7 | grep 'NOTYPE GLOBAL DEFAULT
UN'
2: 00000000 0 NOTYPE GLOBAL DEFAULT UND environ
3: 00000000 0 NOTYPE GLOBAL DEFAULT UND __progname
--
===
Mark Millard
marklmi at yahoo.com
