[dpdk-dev] [PATCH] Don't combine '-r' and '--export-dynamic' linker options

[Rafael Avila de Espindola]

Thomas Monjalon <thomas at monjalon.net> writes:

> 25/10/2019 03:20, Rafael Ávila de Espíndola:
>> Running ld with '-r' switches the linker to a very special mode where
>> some other linker options don't make sense.
>> 
>> In particular, '--export-dynamic' normally requires that all global
>> symbols be included in the dynamic symbol table, but a .o file doesn't
>> even have a dynamic symbol table.
>> 
>> When given both options it looks like the gnu linker just ignores
>> '--export-dynamic'.
>> 
>> Unfortunately some versions of lld (https://lld.llvm.org/) have a bug
>> that causes it to try to create a dynamic symbol table in the output
>> .o file and ends up corrupting it
>> (https://bugs.llvm.org/show_bug.cgi?id=43552). Current (git) version
>> of lld now issues an error.
>> 
>> This patch drops $(LDFLAGS) when using -r. With this patch I can build
>> dpdk with lld.
> [...]
>> -PMDINFO_LD = $(CROSS)ld $(LDFLAGS) -r -o $@.o $@.pmd.o $@
>> +PMDINFO_LD = $(CROSS)ld -r -o $@.o $@.pmd.o $@
>
> Dealing with compiler bugs is really annoying.
> I'm afraid removing LDFLAGS may break in some environments.
> Could you just filter-out some incompatible options?

Sure, that works. I will send a v2.

> And what about meson? Is there some similar issue?

As far as I can tell meson produces a .a file instead. In the
build.ninja file I see

build drivers/librte_pmd_dpaa_event.a: STATIC_LINKER drivers/a715181@@rte_pmd_dpaa_event at sta/meson-generated_.._rte_pmd_dpaa_event.pmd.c.o drivers/a715181@@tmp_rte_pmd_dpaa_event at sta/event_dpaa_dpaa_eventdev.c.o

and

rule STATIC_LINKER
 command = rm -f $out && gcc-ar $LINK_ARGS $out $in

Cheers,
Rafael