[Bug libc/29621] librtld.os: in function `__register_frame': libgcc/unwind-dw2-fde.c:136: undefined reference to `malloc'

["adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29621

--- Comment #12 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
(In reply to Florian Weimer from comment #11)
> (In reply to Adhemerval Zanella from comment #7)
> > Ok, with this one I can see the buildroot failure. It seems that it is
> > misconfiguring the stage1 gcc, where the libgcc.a generated is relying on
> > the libc for unwinding (thus why ld.so link is failing).
> 
> No, this is expected. The libgcc unwinder has depended on glibc symbols for
> many, many years. The unwinder cannot be linked into ld.so.
> 
> Someone needs to use ld tracing to figure out why __register_frame is pulled
> into the ld.so link.

What I am trying to say is buildroot generated stage1 compiler with libgcc.a
for mipsle that is not what glibc expects.  The buildroot symbol trace for
librtld.so shows:

$ /tmp/buildroot/output/host/mipsel-buildroot-linux-gnu/bin/ld [...]
--trace-symbol=__register_frame
/tmp/buildroot/output/host/mipsel-buildroot-linux-gnu/bin/ld:
/tmp/buildroot/output/host/lib/gcc/mipsel-buildroot-linux-gnu/11.3.0/libgcc.a(unwind-dw2-fde-dip.o):
definition of __register_frame

However even the stage2 gcc11 from the build-many-glibc does not links against
the unwinder:

$ mips64el-glibc-linux-gnu-ld -plugin [...] --trace-symbol=__register_frame
$ 

It does not container any unwinder routines:

$ ./bin/mips64el-glibc-linux-gnu-objdump -t
./lib/gcc/mips64el-glibc-linux-gnu/11.3.1/libgcc.a | grep unwind
$ 

It is in fact on libgcc_eh.a:

$ ./bin/mips64el-glibc-linux-gnu-objdump -t
./lib/gcc/mips64el-glibc-linux-gnu/11.3.1/libgcc_eh.a | grep unwind
unwind-dw2.o:     file format elf32-ntradlittlemips
00000000 l    df *ABS*  00000000
/home/azanella/toolchain/src/gcc/libgcc/unwind-dw2.c
unwind-dw2-fde-dip.o:     file format elf32-ntradlittlemips
00000000 l    df *ABS*  00000000
/home/azanella/toolchain/src/gcc/libgcc/unwind-dw2-fde.c
unwind-sjlj.o:     file format elf32-ntradlittlemips
unwind-c.o:     file format elf32-ntradlittlemips
00000000 l    df *ABS*  00000000
/home/azanella/toolchain/src/gcc/libgcc/unwind-pe.h

$ ./bin/mips64el-glibc-linux-gnu-objdump -t
./lib/gcc/mips64el-glibc-linux-gnu/11.3.1/libgcc_eh.a | grep __register_frame
00002090 g     F .text  000000d8 .hidden __register_frame_info_bases
00002168 g     F .text  000000d8 .hidden __register_frame_info
00002240 g     F .text  0000006c .hidden __register_frame
000022b0 g     F .text  000000b0 .hidden __register_frame_info_table_bases
00002360 g     F .text  000000b0 .hidden __register_frame_info_table
00002410 g     F .text  000000d0 .hidden __register_frame_table

I am not sure if this is a multilib issue.

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