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carmcross-compilingyoctoopenembedded

Developing Paho-Mqtt-C Application on Host for Target having libraries

Basically, I have the paho-mqtt-c library installed in my rootfs using Yocto build environment. Since it was already included in meta-oe layer, I simply had to add that recipe to IMAGE_INSTALL_append variable.

I confirmed this by checking the following:

root@am65xx-evm:/usr/lib# ls | grep mqtt
libpaho-mqtt3a.so.1
libpaho-mqtt3a.so.1.0
libpaho-mqtt3as.so.1
libpaho-mqtt3as.so.1.0
libpaho-mqtt3c.so.1
libpaho-mqtt3c.so.1.0
libpaho-mqtt3cs.so.1
libpaho-mqtt3cs.so.1.0

Being a novice with building cross-compiled applications and setting up tool chains, I have a basic question which I couldn't exactly find an answer for.

Now that my target machine has the library installed, how to I develop an application on my host machine running Ubuntu 18.04 LTS?

I can do apt-get install and get the same library, but using the cross compiler to compile the C file, it is not able to see the the MQTT Library.

For example:

~/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc mqtt-test.c -l paho-mqtt3c
mqtt-test.c:4:10: fatal error: MQTTClient.h: No such file or directory
 #include "MQTTClient.h"
          ^~~~~~~~~~~~~~
compilation terminated.
Solution 
  • LICENSE = "GPLv2"
LIC_FILES_CHKSUM = "file://COPYING;md5=b234ee4d69f5fce4486a80fdaf4a4263"

SRC_URI = "file://mqtt-test.c \
           file://COPYING"

S = "${WORKDIR}"
TARGET_CC_ARCH += "${LDFLAGS}"

DEPENDS = "paho-mqtt-c"

do_compile() {
    ${CC} mqtt-test.c -o mqtt-test ${CFLAGS} -lpaho-mqtt3c
}

do_install() {
    install -d ${D}${bindir}
    install -m 0755 ${WORKDIR}/mqtt-test ${D}${bindir}
}

    This is the recipe I used with the following directory structure: enter image description here

    Ignore the lmbench and hello-world - they were a sample from TI's tutorial.

    Notice the DEPENDS = "paho-mqtt-c" Apparently the -lpaho-mqtt3c flag with the do_compile() seemed to work this time.

    I still wonder why I could't simply invoke the Linaro compiler and compile this separately.