[Bug ld/19805] visibility=hidden and .a fails

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19805

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING
                 CC|                            |hjl.tools at gmail dot com

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Felix von Leitner from comment #0)
> Problem 1:
> 
> /usr/bin/ld:
> /hdd/home/leitner/projects/dietlibc-0.32/bin-x86_64/dietlibc.a(perror.o):
> relocation R_X86_64_PC32 against symbol `sys_errlist' can not be used when
> making a shared object; recompile with -fPIC
> 
> This code was already compiled with -fPIC. You can actually tell from the
> relocation, it is PC-relative, i.e. position independent.
> 
> $ nm bin-x86_64/dietlibc.a | grep sys_errlist
> 0000000000000000 R sys_errlist
>                  U sys_errlist
>                  U sys_errlist
> 
> so the symbol is being exported, and somebody else is using it with a PIC
> reference. ld should not be refusing to do this.

Never use nm to report linker issue since it doesn't provide complete info.
Please show me "readelf -sWr bin-x86_64/dietlibc.a | grep sys_errlist" and
provide complete linker command line.

> Note that I compiled all the code with -fvisibility=hidden, and I am also
> passing that flag to gcc when creating the "shared library" PIE binary here,
> to make sure the reference is resolved internally.
> 
> I know that gcc is telling ld about the visibility, because calls are doing
> directly (as opposed to through the PLT).
> 
> Problem 2: .a vs loose object files:
> 
> $ gcc -nostdlib -shared -L/opt/diet/lib-x86_64
> /opt/diet/lib-x86_64/start-pie.o -fpie -fvisibility=hidden -o y c.o d.o
> -isystem /opt/diet/include -D__dietlibc__ /opt/diet/lib-x86_64/libc.a -lgcc
> 
> -> works, produces a working binary.
> 
> $ ar cru x.a c.o d.o
> $ gcc -nostdlib -shared -L/opt/diet/lib-x86_64
> /opt/diet/lib-x86_64/start-pie.o -fpie -fvisibility=hidden -o y x.a -isystem
> /opt/diet/include -D__dietlibc__ /opt/diet/lib-x86_64/libc.a -lgcc
> /opt/diet/lib-x86_64/libc.a(stackgap-pie.o): In function `stackgap_pie':
> stackgap-pie.c:(.text+0x39b): undefined reference to `main'
> /usr/bin/ld: y: hidden symbol `main' isn't defined
> /usr/bin/ld: final link failed: Bad value
> collect2: error: ld returned 1 exit status
> $ nm x.a
> [...]
> d.o:
>                  U _GLOBAL_OFFSET_TABLE_
>                  U __you_tried_to_link_a_dietlibc_object_against_glibc
>                  U foo
> 0000000000000000 T main
>                  U puts

Please place x.a and libc.a between --start-group and --end-group.

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