Math functions not working with "make" in C

Question

I am trying to edit previously developed code. I can successfully edit it and build it with 'cmake' and 'make'. The problem I am running into is using the "atan" function. When I attempt to run 'make' with this change, I get the following error in the commandline:

[  5%] Built target convenience_static
[ 35%] Built target rtlsdr_shared
[ 40%] Built target rtl_adsb
[ 45%] Built target rtl_eeprom
[ 50%] Built target rtl_fm
[ 55%] Built target rtl_power
Linking C executable rtl_sdr
CMakeFiles/rtl_sdr.dir/rtl_sdr.c.o: In function `main':
rtl_sdr.c:(.text.startup+0x2ce): undefined reference to `atanf'
collect2: error: ld returned 1 exit status
make[2]: *** [src/rtl_sdr] Error 1
make[1]: *** [src/CMakeFiles/rtl_sdr.dir/all] Error 2
make: *** [all] Error 2

rtl_sdr.c is the file I am editing. I have included and this is still happening. To make sure I was sane, I made a test c program with 'atan' in it and compiled using 'gcc' and it worked just fine. So I am guessing that my CMake or Make file is not using gcc, but I am not sure. I basically don't know anything about make or cmake.

Any help is appreciated.

Below is my CMakeFile:

# Copyright 2012 OSMOCOM Project
#
# This file is part of rtl-sdr
#
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.


########################################################################
# Project setup
######################################################################## cmake_minimum_required(VERSION 2.6) project(rtlsdr C)

#select the release build type by default to get optimization flags if(NOT CMAKE_BUILD_TYPE)    set(CMAKE_BUILD_TYPE "Release")    message(STATUS "Build type not specified: defaulting to release.") endif(NOT CMAKE_BUILD_TYPE) set(CMAKE_BUILD_TYPE ${CMAKE_BUILD_TYPE} CACHE STRING "")

list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/Modules)

if(NOT LIB_INSTALL_DIR)    set(LIB_INSTALL_DIR lib) endif()

# Set the version information here set(VERSION_INFO_MAJOR_VERSION 0) # increment major on api compatibility changes set(VERSION_INFO_MINOR_VERSION 5) # increment minor on feature-level changes set(VERSION_INFO_PATCH_VERSION git) # increment patch for bug fixes and docs include(Version) # setup version info

########################################################################
# Compiler specific setup
######################################################################## if(CMAKE_COMPILER_IS_GNUCC AND NOT WIN32)
    ADD_DEFINITIONS(-Wall)
    ADD_DEFINITIONS(-Wextra)
    ADD_DEFINITIONS(-Wno-unused-parameter)
    ADD_DEFINITIONS(-Wno-unused)
    ADD_DEFINITIONS(-Wsign-compare)
    ADD_DEFINITIONS(-Wdeclaration-after-statement)
    #http://gcc.gnu.org/wiki/Visibility
    add_definitions(-fvisibility=hidden) endif()

########################################################################
# Find build dependencies
######################################################################## find_package(PkgConfig) find_package(LibUSB) set(THREADS_USE_PTHREADS_WIN32 true) find_package(Threads)

if(NOT LIBUSB_FOUND)
    message(FATAL_ERROR "LibUSB 1.0 required to compile rtl-sdr") endif() if(NOT THREADS_FOUND)
    message(FATAL_ERROR "pthreads(-win32) required to compile rtl-sdr") endif()
########################################################################
# Setup the include and linker paths
######################################################################## include_directories(
    ${CMAKE_SOURCE_DIR}/include
    ${LIBUSB_INCLUDE_DIR}
    ${THREADS_PTHREADS_INCLUDE_DIR} )

#link_directories(
#    ...
#)

# Set component parameters
#set(INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/include CACHE INTERNAL "" FORCE)

########################################################################
# Create uninstall target
######################################################################## configure_file(
    ${CMAKE_SOURCE_DIR}/cmake/cmake_uninstall.cmake.in
    ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake @ONLY)

add_custom_target(uninstall
    ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake )

########################################################################
# Install udev rules
######################################################################## option(INSTALL_UDEV_RULES "Install udev rules for RTL-SDR" OFF) if (INSTALL_UDEV_RULES)
    install (
        FILES rtl-sdr.rules
        DESTINATION "/etc/udev/rules.d"
        COMPONENT "udev"
        ) else (INSTALL_UDEV_RULES)
    message (STATUS "Udev rules not being installed, install them with -DINSTALL_UDEV_RULES=ON") endif (INSTALL_UDEV_RULES)

option(DETACH_KERNEL_DRIVER "Detach kernel driver if loaded" OFF) if (DETACH_KERNEL_DRIVER)
    message (STATUS "Building with kernel driver detaching enabled")
    add_definitions(-DDETACH_KERNEL_DRIVER=1) else (DETACH_KERNEL_DRIVER)
    message (STATUS "Building with kernel driver detaching disabled, use -DDETACH_KERNEL_DRIVER=ON to enable") endif (DETACH_KERNEL_DRIVER)

########################################################################
# Add subdirectories
######################################################################## add_subdirectory(include) add_subdirectory(src)

########################################################################
# Create Pkg Config File
######################################################################## FOREACH(inc ${LIBUSB_INCLUDE_DIR})
    LIST(APPEND RTLSDR_PC_CFLAGS "-I${inc}") ENDFOREACH(inc)

FOREACH(lib ${LIBUSB_LIBRARY_DIRS})
    LIST(APPEND RTLSDR_PC_LIBS "-L${lib}") ENDFOREACH(lib)

# use space-separation format for the pc file STRING(REPLACE ";" " " RTLSDR_PC_CFLAGS "${RTLSDR_PC_CFLAGS}") STRING(REPLACE ";" " " RTLSDR_PC_LIBS "${RTLSDR_PC_LIBS}")

# unset these vars to avoid hard-coded paths to cross environment IF(CMAKE_CROSSCOMPILING)
    UNSET(RTLSDR_PC_CFLAGS)
    UNSET(RTLSDR_PC_LIBS) ENDIF(CMAKE_CROSSCOMPILING)

set(prefix ${CMAKE_INSTALL_PREFIX}) set(exec_prefix \${prefix}) set(libdir \${exec_prefix}/${LIB_INSTALL_DIR}) set(includedir \${prefix}/include)

CONFIGURE_FILE(
    ${CMAKE_CURRENT_SOURCE_DIR}/librtlsdr.pc.in
    ${CMAKE_CURRENT_BINARY_DIR}/librtlsdr.pc @ONLY)

INSTALL(
    FILES ${CMAKE_CURRENT_BINARY_DIR}/librtlsdr.pc
    DESTINATION ${LIB_INSTALL_DIR}/pkgconfig )

########################################################################
# Print Summary
######################################################################## MESSAGE(STATUS "Building for version: ${VERSION} / ${LIBVER}") MESSAGE(STATUS "Using install prefix: ${CMAKE_INSTALL_PREFIX}")

Answer 1

Try adding libm to the target_link_libraries for the build target in your CMakeLists.txt

For example you might have

add_executable (test test.c)
target_link_libraries (test m)