Issues compiling bitcode for redis

[thinkmoore]

A user reached out about an error ingesting redis (https://github.com/redis/redis) using mate-cli oneshot redis.

The initial issue appears to be compatibility with -flto, which redis uses at it's default optimization level. At link time, the compilation logs include the error:

/usr/bin/ld: /opt/mate/llvm-wedlock/bin/../lib/LLVMgold.so: error loading plugin: /opt/mate/llvm-wedlock/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory

Commenting out the relevant lines of the Makefile improves things:

diff --git a/src/Makefile b/src/Makefile
index 7e17f1f83..bd6d11a22 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -16,10 +16,10 @@ release_hdr := $(shell sh -c './mkreleasehdr.sh')
 uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
 uname_M := $(shell sh -c 'uname -m 2>/dev/null || echo not')
 OPTIMIZATION?=-O3
-ifeq ($(OPTIMIZATION),-O3)
-       REDIS_CFLAGS+=-flto
-       REDIS_LDFLAGS+=-flto
-endif
+#ifeq ($(OPTIMIZATION),-O3)
+#      REDIS_CFLAGS+=-flto
+#      REDIS_LDFLAGS+=-flto
+#endif
 DEPENDENCY_TARGETS=hiredis linenoise lua hdr_histogram fpconv
 NODEPS:=clean distclean

But the compilation still fails. It looks like this is because redis' build process uses separate invocations for compiling and linking each final executable:

    LINK redis-server
INFO:Entering CC [-g -ggdb -rdynamic -o redis-server adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o unix.o ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a ../deps/hdr_histogram/libhdrhistogram.a ../deps/fpconv/libfpconv.a ../deps/jemalloc/lib/libjemalloc.a -lm -ldl -pthread -lrt -g3 -grecord-gcc-switches]
DEBUG:Compile using parsed arguments:
InputList:         [-g -ggdb -rdynamic -o redis-server adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o unix.o ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a ../deps/hdr_histogram/libhdrhistogram.a ../deps/fpconv/libfpconv.a ../deps/jemalloc/lib/libjemalloc.a -lm -ldl -pthread -lrt -g3 -grecord-gcc-switches]
InputFiles:        []
ObjectFiles:       [adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o unix.o ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a ../deps/hdr_histogram/libhdrhistogram.a ../deps/fpconv/libfpconv.a ../deps/jemalloc/lib/libjemalloc.a]
OutputFilename:    redis-server
CompileArgs:       [-g -ggdb -g3 -grecord-gcc-switches]
LinkArgs:          [-rdynamic adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o eval.o bio.o rio.o rand.o memtest.o syscheck.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o lolwut6.o acl.o tracking.o socket.o tls.o sha256.o timeout.o setcpuaffinity.o monotonic.o mt19937-64.o resp_parser.o call_reply.o script_lua.o script.o functions.o function_lua.o commands.o strl.o connection.o unix.o ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a ../deps/hdr_histogram/libhdrhistogram.a ../deps/fpconv/libfpconv.a ../deps/jemalloc/lib/libjemalloc.a -lm -ldl -pthread -lrt]
ForbiddenFlags:    []
IsVerbose:         false
IsDependencyOnly:  false
IsPreprocessOnly:  false
IsAssembleOnly:    false
IsAssembly:        false
IsCompileOnly:     false
IsEmitLLVM:        false
IsLTO:             false
IsPrintOnly:       false

DEBUG: We are skipping bitcode generation because we did not see any input files.

After a quick inspection, I wasn't able to track down what emits the final DEBUG message (clang itself?).

[woodruffw]

After a quick inspection, I wasn't able to track down what emits the final DEBUG message (clang itself?).

That looks like it's coming from GLLVM, which is wrapping clang.

[woodruffw]

Specifically, I believe GLLVM doesn't wrap ld at all, so it isn't aware of any embedded bitcode that gets shuffled around there. Maybe there's something we could do with Blight to fix this, like an action that replaces $(LD) with clang in linker mode.