[dpdk-stable] [PATCH] mk: avoid combining -r and -export-dynamic linker options

[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 filters out -export-dynamic from $(LDFLAGS) when using
-r. With this patch I can build dpdk with lld.

Fixes: 3d781ca32874 ("mk: do post processing on objects that register a driver")
Cc: stable at dpdk.org

Signed-off-by: Rafael Ávila de Espíndola <espindola at scylladb.com>
(cherry picked from commit 5a352a3a98e3297555cb08d2db6e45a93ce7e058)
---
Once seastar is updated to use this it should be possible to build
seastar and scylla with lld, which might help with the bots running
out of resources during the link.

 mk/internal/rte.compile-pre.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mk/internal/rte.compile-pre.mk b/mk/internal/rte.compile-pre.mk
index 0cf3791b4..82fe098f7 100644
--- a/mk/internal/rte.compile-pre.mk
+++ b/mk/internal/rte.compile-pre.mk
@@ -61,7 +61,7 @@ CHECK_EXPERIMENTAL = $(EXPERIMENTAL_CHECK) $(SRCDIR)/$(EXPORT_MAP) $@
 
 PMDINFO_GEN = $(RTE_SDK_BIN)/app/dpdk-pmdinfogen $@ $@.pmd.c
 PMDINFO_CC = $(CC) $(CPPFLAGS) $(CFLAGS) $(EXTRA_CFLAGS) -c -o $@.pmd.o $@.pmd.c
-PMDINFO_LD = $(CROSS)ld $(LDFLAGS) -r -o $@.o $@.pmd.o $@
+PMDINFO_LD = $(CROSS)ld -r $(filter-out -export-dynamic,$(LDFLAGS)) -o $@.o $@.pmd.o $@
 PMDINFO_TO_O = if grep -q 'RTE_PMD_REGISTER_.*(.*)' $<; then \
 	echo "$(if $V,$(PMDINFO_GEN),  PMDINFO $@.pmd.c)" && \
 	$(PMDINFO_GEN) && \
-- 
2.24.1