Cannot add C file to Yocto Layer using bitbake - multithreading

Question

I have a C file binary to add as custom layer in the yocto and run in qemu. I have created layer using bitbake-layers create-layer meta-custLayer and added using bitbake-layers add-layer meta-custLayer. The file tree of meta-custLayer is as:
The example_0.1.bb file has the following:
SUMMARY = "bitbake-layers recipe"
DESCRIPTION = "Recipe created by bitbake-layers"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COREBASE}/meta/files/common-licenses/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
SRC_URI = "file://threading.c"
S = "${WORKDIR}"
TARGET_CC_ARCH += "${LDFLAGS}"
do_compile(){
$(CC) threading.c -o threads -lpthreads
}
do_install(){
install -d ${D}${bindir}
install -m 0755 threads
${D}${bindir}s
}
When the command bitbake example is executed, this is the output:
ERROR: example-0.1-r0 do_compile: Execution of '/home/sajil/edm_yocto/sources/poky/build/tmp/work/core2-64-poky-linux/example/0.1-r0/temp/run.do_compile.1806553' failed with exit code 127:
/home/sajil/edm_yocto/sources/poky/build/tmp/work/core2-64-poky-linux/example/0.1-r0/temp/run.do_compile.1806553: 99: CC: not found
/home/sajil/edm_yocto/sources/poky/build/tmp/work/core2-64-poky-linux/example/0.1-r0/temp/run.do_compile.1806553: 99: threading.c: not found
WARNING: exit code 127 from a shell command.
when bitbake core-image-minimal is executed, terminal shows that threads is unbuildable and runs into error:
ERROR: Nothing RPROVIDES 'threads' (but /home/sajil/edm_yocto/sources/poky/meta/recipes-core/images/core-image-minimal.bb RDEPENDS on or otherwise requires it)
NOTE: Runtime target 'threads' is unbuildable, removing...
Missing or unbuildable dependency chain was: ['threads']
ERROR: Required build target 'core-image-minimal' has no buildable providers.
Missing or unbuildable dependency chain was: ['core-image-minimal', 'threads']
I checked the path of the custom layer directory, being correct. I am clueless about the errors I am confronting.
For now my task is to run the C-file (adding it as a layer) on QEMU. I am unable to build the image for the same.
I would appreciate some help and insights!

Answer 1

There is multiple issues on your recipe:
Your do_compile command does not indicate where to find your .c file
You should use ${CC} instead of $(CC)
lpthread does not end with and s
do_compile() {
${CC} ${S}/threading.c -o ${S}/threads -lpthread
}
Your do_install does not provide the correct path to your binary:
do_install() {
install -d ${D}${bindir}
install -m 0755 ${WORKDIR}/threads ${D}${bindir}
}
At the end you should populate the packages:
FILES_${PN} = "${bindir}"
Edit about threads unbuildable:
threads is unbuildable because the recipe does not mention that the package is threads.
Here you have some options:
Rename your recipe to threads_0.1.bb (I recommend you to use a less generic name)
use the PACKAGES variable in your recipe. You will need to modify the FILES_* variable too. (a bit complicated if you are new to Yocto)
Use the current recipe name, and change the IMAGE_INSTALL += "threads" to IMAGE_INSTALL += "example"