opencv - No rule to make target '-L/usr/local/lib'

Question

I am facing a problem while trying to link opencv to CPP project generated by Matlab Coder. In the auto generated Makefile of the project, I added pkg-config --cflags opencv to CFLAGS and pkg-config --libs opencv to LIBS (opencv 3.4), which then gives the error "No rule to make target '-L/usr/local/lib'". Any ideas how to fix ther error?

PRODUCT_NAME              = runeef
MAKEFILE                  = runeef_rtw.mk
MATLAB_ROOT               = /usr/local/Polyspace/R2020a
MATLAB_BIN                = /usr/local/Polyspace/R2020a/bin
MATLAB_ARCH_BIN           = $(MATLAB_BIN)/glnxa64
MASTER_ANCHOR_DIR         = 
START_DIR                 = /home/dell/Documents/purefusion/codegen/exe/runeef
TGT_FCN_LIB               = ISO_C++11
SOLVER_OBJ                = 
CLASSIC_INTERFACE         = 0
MODEL_HAS_DYNAMICALLY_LOADED_SFCNS = 
RELATIVE_PATH_TO_ANCHOR   = .
C_STANDARD_OPTS           = -fwrapv -ansi -pedantic -Wno-long-long
CPP_STANDARD_OPTS         = -fwrapv -std=c++11 -pedantic

###########################################################################
## TOOLCHAIN SPECIFICATIONS
###########################################################################

# Toolchain Name:          GNU gcc/g++ | gmake (64-bit Linux)
# Supported Version(s):    
# ToolchainInfo Version:   2020a
# Specification Revision:  1.0
# 
#-------------------------------------------
# Macros assumed to be defined elsewhere
#-------------------------------------------

# C_STANDARD_OPTS
# CPP_STANDARD_OPTS

#-----------
# MACROS
#-----------

WARN_FLAGS         = -Wall -W -Wwrite-strings -Winline -Wstrict-prototypes -Wnested-externs -Wpointer-arith -Wcast-align
WARN_FLAGS_MAX     = $(WARN_FLAGS) -Wcast-qual -Wshadow
CPP_WARN_FLAGS     = -Wall -W -Wwrite-strings -Winline -Wpointer-arith -Wcast-align
CPP_WARN_FLAGS_MAX = $(CPP_WARN_FLAGS) -Wcast-qual -Wshadow

TOOLCHAIN_SRCS = 
TOOLCHAIN_INCS = 
TOOLCHAIN_LIBS = 

#------------------------
# BUILD TOOL COMMANDS
#------------------------

# C Compiler: GNU C Compiler
CC = gcc

# Linker: GNU Linker
LD = g++

# C++ Compiler: GNU C++ Compiler
CPP = g++

# C++ Linker: GNU C++ Linker
CPP_LD = g++

# Archiver: GNU Archiver
AR = ar

# MEX Tool: MEX Tool
MEX_PATH = $(MATLAB_ARCH_BIN)
MEX = "$(MEX_PATH)/mex"

# Download: Download
DOWNLOAD =

# Execute: Execute
EXECUTE = $(PRODUCT)

# Builder: GMAKE Utility
MAKE_PATH = %MATLAB%/bin/glnxa64
MAKE = "$(MAKE_PATH)/gmake"


#-------------------------
# Directives/Utilities
#-------------------------

CDEBUG              = -g
C_OUTPUT_FLAG       = -o
LDDEBUG             = -g
OUTPUT_FLAG         = -o
CPPDEBUG            = -g
CPP_OUTPUT_FLAG     = -o
CPPLDDEBUG          = -g
OUTPUT_FLAG         = -o
ARDEBUG             =
STATICLIB_OUTPUT_FLAG =
MEX_DEBUG           = -g
RM                  = @rm -f
ECHO                = @echo
MV                  = @mv
RUN                 =

#--------------------------------------
# "Faster Runs" Build Configuration
#--------------------------------------

ARFLAGS              = ruvs
CFLAGS               = $(shell pkg-config --cflags opencv) -c $(C_STANDARD_OPTS)  -fPIC 
                       -O3 -fno-loop-optimize -fno-aggressive-loop-optimizations
CPPFLAGS             = $(shell pkg-config --cflags opencv) -c $(CPP_STANDARD_OPTS) -fPIC 
                       -O3 -fno-loop-optimize -fno-aggressive-loop-optimizations
CPP_LDFLAGS          = -Wl,-rpath,"$(MATLAB_ARCH_BIN)",-L"$(MATLAB_ARCH_BIN)"
CPP_SHAREDLIB_LDFLAGS  = -shared -Wl,-rpath,"$(MATLAB_ARCH_BIN)",-L"$(MATLAB_ARCH_BIN)" -Wl,--no-undefined
DOWNLOAD_FLAGS       =
EXECUTE_FLAGS        =
LDFLAGS              = -Wl,-rpath,"$(MATLAB_ARCH_BIN)",-L"$(MATLAB_ARCH_BIN)"
MEX_CPPFLAGS         =
MEX_CPPLDFLAGS       =
MEX_CFLAGS           =
MEX_LDFLAGS          =
MAKE_FLAGS           = -f $(MAKEFILE)
SHAREDLIB_LDFLAGS    = -shared -Wl,-rpath,"$(MATLAB_ARCH_BIN)",-L"$(MATLAB_ARCH_BIN)" -Wl,--no-undefined



###########################################################################
## OUTPUT INFO
###########################################################################

PRODUCT = /home/dell/Documents/purefusion/runeef
PRODUCT_TYPE = "executable"
BUILD_TYPE = "Executable"

###########################################################################
## INCLUDE PATHS
###########################################################################

INCLUDES_BUILDINFO = -I$(START_DIR) -I/home/dell/Documents/purefusion -I$(MATLAB_ROOT)/extern/include -I$(MATLAB_ROOT)/toolbox/vision/builtins/src/ocv/include -I$(MATLAB_ROOT)/toolbox/vision/builtins/src/ocvcg/opencv/include -I/home/dell/Documents/purefusion/codegen/exe 

INCLUDES = $(INCLUDES_BUILDINFO)

###########################################################################
## DEFINES
###########################################################################

DEFINES_CUSTOM = 
DEFINES_STANDARD = -DMODEL=runeef

DEFINES = $(DEFINES_CUSTOM) $(DEFINES_STANDARD)

###########################################################################
## SOURCE FILES
###########################################################################

SRCS = $(START_DIR)/rt_nonfinite.cpp $(START_DIR)/rtGetNaN.cpp $(START_DIR)/rtGetInf.cpp $(MATLAB_ROOT)/toolbox/vision/builtins/src/ocv/detectFASTCore.cpp $(MATLAB_ROOT)/toolbox/vision/builtins/src/ocv/cgCommon.cpp $(MATLAB_ROOT)/toolbox/vision/builtins/src/ocv/extractFreakCore.cpp $(MATLAB_ROOT)/toolbox/vision/builtins/src/ocv/mwfreak.cpp /home/dell/Documents/purefusion/codegen/exe/main.cpp $(START_DIR)/runeef_rtwutil.cpp $(START_DIR)/runeef_data.cpp $(START_DIR)/runeef_initialize.cpp $(START_DIR)/runeef_terminate.cpp $(START_DIR)/runeef.cpp $(START_DIR)/colon.cpp $(START_DIR)/string1.cpp $(START_DIR)/rgb2gray.cpp $(START_DIR)/abs.cpp $(START_DIR)/histeq.cpp $(START_DIR)/minOrMax.cpp $(START_DIR)/sum.cpp $(START_DIR)/imhist.cpp $(START_DIR)/bsxfun.cpp $(START_DIR)/cornerPoints_cg.cpp $(START_DIR)/FeaturePointsImpl.cpp $(START_DIR)/repmat.cpp $(START_DIR)/extractFeatures.cpp $(START_DIR)/mod.cpp $(START_DIR)/eef.cpp $(START_DIR)/remapFun.cpp $(START_DIR)/prod.cpp $(START_DIR)/imfilter.cpp $(START_DIR)/padarray.cpp $(START_DIR)/multiscaleBlendingColor.cpp $(START_DIR)/gaussian_pyramid.cpp $(START_DIR)/laplacian_pyramid.cpp $(START_DIR)/upsample.cpp $(START_DIR)/reconstruct_laplacian_pyramid.cpp $(START_DIR)/robustNormalization.cpp $(START_DIR)/sort.cpp $(START_DIR)/sortIdx.cpp

ALL_SRCS = $(SRCS)

###########################################################################
## OBJECTS
###########################################################################

OBJS = rt_nonfinite.o rtGetNaN.o rtGetInf.o detectFASTCore.o cgCommon.o extractFreakCore.o mwfreak.o main.o runeef_rtwutil.o runeef_data.o runeef_initialize.o runeef_terminate.o runeef.o colon.o string1.o rgb2gray.o abs.o histeq.o minOrMax.o sum.o imhist.o bsxfun.o cornerPoints_cg.o FeaturePointsImpl.o repmat.o extractFeatures.o mod.o eef.o remapFun.o prod.o imfilter.o padarray.o multiscaleBlendingColor.o gaussian_pyramid.o laplacian_pyramid.o upsample.o reconstruct_laplacian_pyramid.o robustNormalization.o sort.o sortIdx.o

ALL_OBJS = $(OBJS)

###########################################################################
## PREBUILT OBJECT FILES
###########################################################################

PREBUILT_OBJS = 

###########################################################################
## LIBRARIES
###########################################################################

LIBS = $(MATLAB_ROOT)/bin/glnxa64/libmwjpegreader.so $(MATLAB_ROOT)/bin/glnxa64/libopencv_calib3d.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_core.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_features2d.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_flann.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_imgproc.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_ml.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_objdetect.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_video.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudaarithm.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudabgsegm.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudafeatures2d.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudafilters.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudaimgproc.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudalegacy.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudaobjdetect.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudaoptflow.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudastereo.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudawarping.so.3.4 $(MATLAB_ROOT)/bin/glnxa64/libopencv_cudev.so.3.4 $(shell pkg-config --libs opencv)
#/usr/local/lib/libopencv_core.so.4.5.1 /usr/local/lib/libopencv_imgcodecs.so.4.5.1 /usr/local/lib/libopencv_highgui.so.4.5.1

###########################################################################
## SYSTEM LIBRARIES
###########################################################################

SYSTEM_LIBS =  -L"$(MATLAB_ROOT)/bin/glnxa64" -lmwrgb2gray_tbb -lmwgetnumcores -lmwtbbhist -lmwgrayxform_tbb -lmwgrayto8 -lmwippfilter -lmwipp -lmwimfilter -lmwnhood -lm -lstdc++ 

###########################################################################
## ADDITIONAL TOOLCHAIN FLAGS
###########################################################################

#---------------
# C Compiler
#---------------

CFLAGS_ = -Wno-variadic-macros -Wno-variadic-macros
CFLAGS_BASIC = $(DEFINES) $(INCLUDES)

CFLAGS += $(CFLAGS_) $(CFLAGS_BASIC) 

#-----------------
# C++ Compiler
#-----------------

CPPFLAGS_ = -Wno-variadic-macros -Wno-variadic-macros
CPPFLAGS_BASIC = $(DEFINES) $(INCLUDES)

CPPFLAGS += $(CPPFLAGS_) $(CPPFLAGS_BASIC)

###########################################################################
## INLINED COMMANDS
###########################################################################

###########################################################################
## PHONY TARGETS
###########################################################################

.PHONY : all build buildobj clean info prebuild download execute


all : build
    @echo "### Successfully generated all binary outputs."


build : prebuild $(PRODUCT)


buildobj : prebuild $(OBJS) $(PREBUILT_OBJS) $(LIBS) 
    @echo "### Successfully generated all binary outputs."


prebuild : 


download : $(PRODUCT)


execute : download
    @echo "### Invoking postbuild tool "Execute" ..."
    $(EXECUTE) $(EXECUTE_FLAGS)
    @echo "### Done invoking postbuild tool."


###########################################################################
## FINAL TARGET
###########################################################################

#-------------------------------------------
# Create a standalone executable            
#-------------------------------------------

$(PRODUCT) : $(OBJS) $(PREBUILT_OBJS) $(LIBS)
    @echo "### Creating standalone executable "$(PRODUCT)" ..."
    $(CPP_LD) $(CPP_LDFLAGS) -o $(PRODUCT) $(OBJS) -Wl,--start-group $(LIBS) -Wl,--end-group $(SYSTEM_LIBS) $(TOOLCHAIN_LIBS) 
    @echo "### Created: $(PRODUCT)"


###########################################################################
## INTERMEDIATE TARGETS
###########################################################################

#---------------------
# SOURCE-TO-OBJECT
#---------------------

%.o : %.c
    $(CC) $(CFLAGS) -o "$@" "$<"


%.o : %.cpp
    $(CPP) $(CPPFLAGS) -o "$@" "$<"


%.o : $(RELATIVE_PATH_TO_ANCHOR)/%.c
 

Answer 1

Your makefile has the variable assignment (edited for brevity)...

LIBS = $(MATLAB_ROOT)/bin/glnxa64/libmwjpegreader.so ... $(shell pkg-config --libs opencv)

Where the $(shell pkg-config --libs opencv) component will expand to something like...

-L/usr/local/lib -lopencv

But you then use $(LIBS) as a dependency for several targets, e.g...

$(PRODUCT) : $(OBJS) $(PREBUILT_OBJS) $(LIBS)

which expands to (again, edited for brevity)...

$(PRODUCT) : $(OBJS) $(PREBUILT_OBJS) -L/usr/local/lib -lopencv

Hence, when make attempts to process the target $(PRODUCT) it will see that the target seemingly depends on -L/usr/local/lib and act accordingly.

It's difficult to provide a more complete answer without more context but $(LIBS) probably shouldn't be listed as a dependency for this or any other targets.