Undefined reference when using ta-lib/ta_lib.h file and Makefile-CodePudding

I want to use the ta_lib functions in my C code and am trying to import the ta_lib functions. The header file gets imported correctly but i cannot get the linker to find the actual library. I want to do the compiling process with MAKE and gcc.

Firstly I import the header

#include <ta-lib/ta_libc.h>

And then when i need to use a function


TA_ADOSC(0, CSV_LENGTH - 1, temp_high, temp_low, temp_close, temp_volume, 3, 10, &beginIdx, &endIdx, tmp_adosc);

The program compiles fine using my makefile


# create CC variable

CC = gcc

# create CFLAGS variable

CFLAGS =  -L/usr/local/lib -Wall -g

LDLIBS = -lta_lib -I/usr/local/include -lm

output: main.o
$(CC) $(CFLAGS) -o output main.o

main.o: main.c
$(CC) $(LDLIBS) -c main.c

# target: dependencies

# action

clean:
rm -f \*.o output

Once I try to run make i get the following


gcc -L/usr/local/lib -Wall -g -o output main.o
/usr/bin/ld: main.o: in function `calculate_indicators': main.c:(.text 0x226): undefined reference to `TA_ADOSC'
collect2: error: ld returned 1 exit status
make: \*\*\* \[Makefile:10: output\] Error 1

From my understanding I need to fix the linking to the shared library.

The library is installed:


ldconfig -p | grep libta_lib.so

Returns the following


    libta_lib.so.0 (libc6,x86-64) => /usr/local/lib/libta_lib.so.0
    libta_lib.so.0 (libc6,x86-64) => /lib/libta_lib.so.0
    libta_lib.so (libc6,x86-64) => /usr/local/lib/libta_lib.so
    libta_lib.so (libc6,x86-64) => /lib/libta_lib.so

Since i am fairly new to C and using external libraries I can't find what seems to be the problem

CodePudding user response：

You are adding the libraries to the compile line. They need to be added to the link line. And preprocessor options like -I are used by the compiler, and "where to find libraries" options like -L are used by the linker.

Also, libraries always must come at the end of the link line, after all the object files. And, the -L "where to search" option should come before the -l "what library to find" option.

Write your rules like this:

CFLAGS = -I/usr/local/include -Wall -g
LDFLAGS = -L/usr/local/lib
LDLIBS = -lta_lib -lm

output: main.o
        $(CC) $(CFLAGS) $(LDFLAGS) -o output main.o $(LDLIBS)

main.o: main.c
        $(CC) $(CFLAGS) -c main.c

However, it's better to just let make do the work for you; it knows how to correctly compile things (as long as you set the standard variables). You don't need to include a rule to build main.o at all.