Include libfyaml as libary with cmake

[pilotmoritz]

Hi Folks,
I am struggling since some time to include an external libary to my project, in this case it is libfyaml for parasing YAML files from SD card.
The libfyaml also comes with a CMakeList.txt for building itself.
The project folder structure is:
-- CMakeList.txt
-- src/
-- -- main.c
-- libfyaml/
-- -- CMakeList.txt
-- -- include/
-- -- -- libfyaml.h
-- -- src/../
-- -- -- loadsoffiles.c

My global CMakeList.txt looks like that:

cmake_minimum_required(VERSION 3.20.0)
set(PM_STATIC_YML_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pm_static.yml)
list(APPEND mcuboot_OVERLAY_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/mcuboot_overlay-rsa.conf")
find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
project(mass)
FILE(GLOB app_sources src/*.c)
target_sources(app PRIVATE ${app_sources})

#Add external lib
add_library(libfyaml "${CMAKE_CURRENT_SOURCE_DIR}/libfyaml/include/libfyaml.h")
target_link_libraries(app PRIVATE libfyaml)

When building it throws an error: CMake Error: CMake can not determine linker language for target: libfyaml And I don't really know what I can do about it.

Another approach:
When I replace add_libary() and target_link_libraries() with add_subdirectory("${CMAKE_CURRENT_SOURCE_DIR}/libfyaml") it cannot find sys/termios.h, which tells me that something like the zephyr base is not included while it was compiled.

Anyone has a suggestion how to proceed? Which approach should I take and is there a way to get arround those erroros?
I have seen, that there are other threads with a similar topics, which helped, but it's still not successfull.

Thanks for your help, I really appreciate it!

[wjabozzo]

I am aware this issue is old, but I am having the exact same problem. I've also tried the add_library and add_subdirectory approach with the same results.

[nylnx]

If you get stuck at this step you first need to understand CMake. This is not a Zephyr problem, but rather a CMake problem. And yes, it is hard to link a Zephyr app with a random library from the internet, but if you do it correctly and go step by step, you might have a chance as long as the library can even be used on your target system.

[yashi]

This is a complete minimal working example of how to make libfyaml a Zephyr module.

This example consists of configuration files for libfyaml Zephyr module, CMakeLists.txt and Kconfig, and a sample app which calls fy_library_version().

The module and a sample app in a diff format.

diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..bda441e
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+set(MODULE_EXT_ROOT ${CMAKE_CURRENT_LIST_DIR})
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(libfyaml-sample)
+
+target_sources(app PRIVATE src/main.c)
diff --git a/modules/libfyaml/CMakeLists.txt b/modules/libfyaml/CMakeLists.txt
new file mode 100644
index 0000000..32533d5
--- /dev/null
+++ b/modules/libfyaml/CMakeLists.txt
@@ -0,0 +1,30 @@
+if(CONFIG_LIBFYAML)
+  zephyr_interface_library_named(libfyaml)
+  target_include_directories(libfyaml INTERFACE ${ZEPHYR_CURRENT_MODULE_DIR}/include)
+
+  zephyr_library()
+  zephyr_library_include_directories(
+    ${ZEPHYR_CURRENT_MODULE_DIR}/src
+    ${ZEPHYR_CURRENT_MODULE_DIR}/src/lib
+    ${ZEPHYR_CURRENT_MODULE_DIR}/src/xxhash
+    ${ZEPHYR_CURRENT_MODULE_DIR}/src/util
+  )
+  zephyr_library_compile_definitions(VERSION="0.8")
+  zephyr_library_compile_definitions(
+    _GNU_SOURCE=1
+    NDEBUG=1
+    FY_DEVMODE=1
+  )
+  zephyr_library_compile_options(
+    -Wno-pointer-arith
+    -Wno-return-type
+    -std=gnu99
+  )
+
+  zephyr_library_sources(
+    ${ZEPHYR_CURRENT_MODULE_DIR}/src/lib/fy-parse.c
+  )
+
+  zephyr_library_link_libraries(libfyaml)
+
+endif()
diff --git a/modules/libfyaml/Kconfig b/modules/libfyaml/Kconfig
new file mode 100644
index 0000000..95e6fd3
--- /dev/null
+++ b/modules/libfyaml/Kconfig
@@ -0,0 +1,10 @@
+config LIBFYAML
+	bool "libfyaml"
+
+if LIBFYAML
+
+config APP_LINK_WITH_LIBFYAML
+	bool "Link 'app' with libfyaml"
+	default y
+
+endif
diff --git a/modules/modules.cmake b/modules/modules.cmake
new file mode 100644
index 0000000..bc138c9
--- /dev/null
+++ b/modules/modules.cmake
@@ -0,0 +1,2 @@
+set(ZEPHYR_LIBFYAML_CMAKE_DIR ${CMAKE_CURRENT_LIST_DIR}/libfyaml)
+set(ZEPHYR_LIBFYAML_KCONFIG   ${CMAKE_CURRENT_LIST_DIR}/libfyaml/Kconfig)
diff --git a/prj.conf b/prj.conf
new file mode 100644
index 0000000..2afdb01
--- /dev/null
+++ b/prj.conf
@@ -0,0 +1,2 @@
+CONFIG_LIBFYAML=y
+CONFIG_PICOLIBC=y
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..a0ef54b
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,8 @@
+#include <zephyr/kernel.h>
+
+#include <libfyaml.h>
+
+void main(void)
+{
+	printk("Hello World! %s\n", fy_library_version());
+}
diff --git a/west.yml b/west.yml
new file mode 100644
index 0000000..18109df
--- /dev/null
+++ b/west.yml
@@ -0,0 +1,18 @@
+manifest:
+
+  projects:
+    - name: zephyr
+      url: https://github.com/zephyrproject-rtos/zephyr
+      revision: main
+      path: zephyr
+      west-commands: scripts/west-commands.yml
+      import:
+        name-allowlist:
+          - cmsis
+          - hal_stm32
+          - picolibc
+
+    - name: libfyaml
+      url: /tmp/ws/repos/libfyaml
+      revision: zephyr
+      path: modules/lib/libfyaml

To use it you need a modified version of libfyaml repository. A modification must be made on libfyaml to have zephyr/module.yml. The example assume that the repo is at /tmp/ws/repos/libfyaml, but you can point at anywhere. See https://docs.zephyrproject.org/latest/develop/west/manifest.html for more detail.
To understand why you need zephyr/module.yml, please read https://docs.zephyrproject.org/latest/develop/modules.html.

zephyr/module.yml in diff format.

diff --git a/zephyr/module.yml b/zephyr/module.yml
new file mode 100644
index 0000000..ab1e2b0
--- /dev/null
+++ b/zephyr/module.yml
@@ -0,0 +1,3 @@
+build:
+  cmake-ext: True
+  kconfig-ext: True

This example is minimal because it only compiles src/lib/fy-parse.c from libfyaml. Even for src/lib/fy-parse.c to work, I have to comment out a few places in libfyaml:

A few commented out lines

 diff --git a/src/lib/fy-parse.c b/src/lib/fy-parse.c
index f53362a..ae3ce7a 100644
--- a/src/lib/fy-parse.c
+++ b/src/lib/fy-parse.c
@@ -11,10 +11,10 @@
 
 #include <stdio.h>
 #include <string.h>
-#include <sys/mman.h>
+//#include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/ioctl.h>
+//#include <sys/ioctl.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <assert.h>
diff --git a/src/lib/fy-types.c b/src/lib/fy-types.c
index 1649e04..ed1a225 100644
--- a/src/lib/fy-types.c
+++ b/src/lib/fy-types.c
@@ -11,7 +11,6 @@
 
 #include <stdio.h>
 #include <string.h>
-#include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
diff --git a/src/util/fy-utils.h b/src/util/fy-utils.h
index 8644898..dd6598b 100644
--- a/src/util/fy-utils.h
+++ b/src/util/fy-utils.h
@@ -16,7 +16,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <unistd.h>
-#include <termios.h>
+//#include <termios.h>
 
 #if defined(__APPLE__) && (_POSIX_C_SOURCE < 200809L)
 FILE *open_memstream(char **ptr, size_t *sizeloc);
@@ -52,8 +52,8 @@ int fy_tag_scan(const char *data, size_t len, struct fy_tag_scan_info *info);
 #define FY_UNUSED /* nothing */
 #endif
 
-int fy_term_set_raw(int fd, struct termios *oldt);
-int fy_term_restore(int fd, const struct termios *oldt);
+//int fy_term_set_raw(int fd, struct termios *oldt);
+//int fy_term_restore(int fd, const struct termios *oldt);
 ssize_t fy_term_write(int fd, const void *data, size_t count);
 int fy_term_safe_write(int fd, const void *data, size_t count);
 ssize_t fy_term_read(int fd, void *data, size_t count, int timeout_us);

To make complete libyaml Zephyr module, you need to

• Add srouce file to zephyr_library_sources() in libfyaml-sample/modules/libfyaml/CMakeLists.txt
• Add compile definitions if needed
• Add compile options if needed
• Fix souce code of libfyaml if needed.

Last but not least, libfyaml is GPL 2.0. Make sure you know what that means.

Happy Hacking,

[wjabozzo]

Thank you for the help!

I've solved the original issue, now I am facing other problems. I don't want to hijack this discussion since it is specifically about including libfyaml and that has been anwsered. I'll create another discussion if the new problem ends up being too unwieldly.

[anujdeshpande]

@yashi were you able to get to a place where you could parse strings (or files) under zephyr with libfyaml? I have been look at it (your instructions helped!) and it seems like there's a huge number of changes needed to even search a string for a particular key value pair.

I tried to get to the above state by using the fy_document_build_from_string function - so added fy-doc to the cmake - along with fy-parse. Did you do something similar>

[yashi]

I don't think I did.

[yashi]

what kind of changes have you done?