Re: Static linking of musl with code compiled using GNU header files

[David Grothe <dave@gcom.com>]

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Thanks for the suggestions.

My musl build did not include a libgcc:

linuxsvr:dave:musl-0.9.15> find . -name '*libgcc*'
linuxsvr:dave:musl-0.9.15>

It is correct that something in the GNU headers changed "signal" into 
"sysv_signal" without my knowledge.

My code base is several million lines of code and I have many other 
projects to do that are higher priority than porting to another set of 
header files.  It would be a few days worth of effort and I just have 
other things to do right now.

That said I do have a reason for wanting static linking, so maybe I will 
find the time to do the port some time. (I tried just aiming my build at 
the musl include directory and it did not "just work".)

I can act on the suggestions made and see how that helps.  But what 
about libgcc?

Thanks,
Dave

On 3/14/2014 11:29 AM, Szabolcs Nagy wrote:
> * David Grothe <dave@gcom.com> [2014-03-14 10:47:31 -0500]:
>> I have a very large code base that I have been compiling on Linux
>> using the standard GNU C compiler [gcc (Ubuntu/Linaro
>> 4.6.3-1ubuntu5) 4.6.3].  I have been using shared object libraries,
>> but for reasons of software support I would now like to link all my
>> commands (a couple of dozen) and daemons using static libraries so
>> that the code files are self-contained and can be copied, along with
>> a core file, to any server back in my shop for analysis.  With
>> dynamic libraries I have to have exactly the same version of libc
>> installed on the machine that I use to examine the core file as were
>> present on the machine that generated the core file, or else gdb
>> will not produce a stack back trace with file and line number
>> information.  So much for the background.
>>
>> I really don't want to port my code base to using the musl header
>> files.  I want to keep compiling with the GNU headers.  When I do
> compiling with the gnu headers is broken and
> it depends on the cflags used
>
>> this and link my-huge-program.o with musl libc.a I get the following
>> list of unresolved externals:
>>
>>           U __divdi3
> comes from libgcc.a, if it's missing you have a toolchain issue
>
>>           w __fini_array_end
>>           w __fini_array_start
> i think musl supports init/fini arrays
> (see src/exit/exit.c)
>
>>           U __moddi3
> libgcc
>
>>           U __sysv_signal
> you may want to replace it with signal
>
>>           U __udivdi3
>>           U __umoddi3
> libgcc
>
>>           U __vfprintf_chk
>>           U __vsnprintf_chk
>>           U __vsprintf_chk
> there are many _chk functions for _FORTIFY_SOURCE, musl may provide
> these eventually, until then you can add your own chk.o with dummy
> implementations (possibly with the safety checks i omit here):
>
> int __vfprintf_chk(FILE *f, int flag, const char *fmt, va_list ap)
> {
> 	return vfprintf(f, fmt, ap);
> }
> int __vsnprintf_chk(char *s, size_t n, int flag, size_t size, const char *fmt, va_list ap)
> {
> 	return vsnprintf(s, n, fmt, ap);
> }
> int __vsprintf_chk(char *s, int flag, size_t size, const char *fmt, va_list ap)
> {
> 	return vsprintf(s, fmt, ap);
> }
>
>>           U __sysv_signal
> use signal
>
>> So, I am wondering if the musl library could at some point provide
>> these routines to enable users to do what I am trying to do.
> compiling with glibc headers and then linking to musl
> cannot be supported in general, because of ABI compat issues
>
> (eg glibc headers define PTHREAD_*_INITIALIZER macros that hardcode
> glibc internal ABI at compile time that does not match musl)
>
> if you are sure you don't have such ABI breakage (see glibc
> vs musl differences on the wiki) then you may get away by
> adding a glibc-compat.o to your musl build
>
>> Any possibility of that?
>>
>> Thanks,
>> Dave


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