[cfe-dev] Clang Linking error: undefined reference to function calls added by LLVM pass

[ALSAYED, DANISH IBRAHIM MOHAMED IBRAHIM via cfe-dev]

Hi all,

I have been stuck on this error for long now and I really need help!.

So I am following this tutorial
https://www.cs.cornell.edu/~asampson/blog/llvm.html to make a pass that
instruments a program by adding calls to an external function (which is
logop in rtlib.c). But unlike the tutorial I am trying to instrument a
larger code-base which is masstree:https://github.com/kohler/masstree-beta.

So as instructed for masstree I run ./configure first but then I edit the
generated Makefile to use clang (instead of gcc/g++) and run my pass. I
also add rtlib.c in the masstree source files so that it gets converted to
rtlib.o with the rest of the masstree source files. Here is the relevant
part of the modified Makefile with my changes highlighted with an arrow (I
also added the $(rtlib) to link it with other .o files to generate
executables):

AR = ar
rtlib = rtlib.o  <===
CC2 = clang -w -v -Xclang -load -Xclang
/.../llvm-3.4/Release+Asserts/lib/SkeletonPass.so `llvm-config
--cflags`
CXX2 = clang++ -v -w -Xclang -load -Xclang
/.../llvm-3.4/Release+Asserts/lib/SkeletonPass.so -std=c++11
`llvm-config --cppflags --libs --cflags --cxxflags core --ldflags`
<===
CC = clang -v <===
CXX = clang++ -v -std=c++11 <===
CPPFLAGS =
CXXFLAGS = -g -W -Wall -O3
DEPSDIR := .deps
DEPCFLAGS = -MD -MF $(DEPSDIR)/$*.d -MP
ifeq ($(strip $(MEMMGR)), )
  MEMMGR =
endif
ifneq ($(strip $(KEYSWAP)), )
  CPPFLAGS += -DKEYSWAP
endif
ifneq ($(strip $(NOPREFETCH)), )
  CPPFLAGS += -DNOPREFETCH
endif
ifneq ($(strip $(NOSUPERPAGE)), )
  CPPFLAGS += -DNOSUPERPAGE
endif
LIBS =  -lpthread -lm
LDFLAGS =

all: test_atomics mtd mtclient mttest

%.o: %.c config.h $(DEPSDIR)/stamp
    $(CXX2) $(CPPFLAGS) $(CXXFLAGS) $(DEPCFLAGS) -include config.h -c -o $@ $<

%.o: %.cc config.h $(DEPSDIR)/stamp
    $(CXX2) $(CPPFLAGS) $(CXXFLAGS) $(DEPCFLAGS) -include config.h -c -o $@ $<

%.S: %.o
    objdump -S $< > $@

libjson.a: json.o string.o straccum.o str.o msgpack.o \
    clp.o kvrandom.o compiler.o memdebug.o kvthread.o
    @/bin/rm -f $@
    $(AR) cru $@ $^

KVTREES = query_masstree.o \
    value_string.o value_array.o value_versioned_array.o \
    string_slice.o

mtd: mtd.o log.o checkpoint.o file.o misc.o $(rtlib) $(KVTREES) \
    kvio.o libjson.a
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

mtclient: mtclient.o misc.o testrunner.o kvio.o $(rtlib) libjson.a
    $(CXX) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) $(LIBS)

mttest: mttest.o misc.o checkpoint.o $(rtlib) $(KVTREES) testrunner.o \
    kvio.o libjson.a
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

test_string: test_string.o string.o $(rtlib) straccum.o compiler.o
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

test_atomics: test_atomics.o string.o straccum.o kvrandom.o $(rtlib) \
    json.o compiler.o kvio.o
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

jsontest: jsontest.o string.o straccum.o json.o compiler.o $(rtlib)
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

msgpacktest: msgpacktest.o string.o straccum.o json.o compiler.o
msgpack.o $(rtlib)
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

scantest: scantest.o compiler.o misc.o $(rtlib) $(KVTREES) libjson.a
    $(CXX) $(CXXFLAGS) -o $@ $^ $(MEMMGR) $(LDFLAGS) $(LIBS)

I use CC2 and CXX2 to generate the instrumented .o files while CC and CXX
to link them into executables. Here is the error I get when I run make:

mtd.o: In function main': /home/.../masstree-beta-master/mtd.cc:730:
undefined reference tologop' /home/.../masstree-beta-master/mtd.cc:730:
undefined reference to logop' /home/.../masstree-beta-master/mtd.cc:732:
undefined reference tologop' /home/.../masstree-beta-master/mtd.cc:732:
undefined reference to logop' /home/.../masstree-beta-master/mtd.cc:736:
undefined reference tologop'
mtd.o:/home/.../masstree-beta-master/mtd.cc:736: more undefined references
to `logop' follow clang: error: linker command failed with exit code 1 (use
-v to see invocation) make: *** [mtd] Error 1.

Any Idea on why is the reference to my function logop (which is in rtlib.c)
undefined even though I add rtlib.o in the linking part to generate
executables?

The question is posted on StackOverflow as well:
http://stackoverflow.com/questions/41650417/clang-linking-error-undefined-reference-to-function-calls-added-by-llvm-pass

Please help! Thank you so much!
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