libc/picolibc: Use libc-level PICOLIBC_MODULE to control picolibc mode

C++ is supported with picolibc only when the toolchain version of picolibc
is use -- libstdc++ must be built with picolibc support and libstdc++ is
included with the toolchain. That creates a circular dependency if the
control of whether to use the module is placed under the picolibc
configuration block (as PICOLIBC_USE_MODULE is).

Make an explicit PICOLIBC_MODULE variable at the libc level to be the
user-visible control for this feature and make code depending on whether
the picolibc module should be used depend on both PICOLIBC and
PICOLIBC_MODULE.

Change PICOLIBC_USE_MODULE to be a hidden configuration variable that the
picolibc module cmake files can use to determine whether to include the
picolibc module sources in the zephyr application build. This symbol can be
removed when the picolibc module is updated to use PICOLIBC AND
PICOLIBC_MODULE instead

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

CMakeLists.txt

@@ -695,7 +695,7 @@ add_custom_command(
 # Make sure Picolibc is built before the rest of the system; there's no explicit
 # reference to any of the files as they're all picked up by various compiler
 # settings
-if(CONFIG_PICOLIBC_USE_MODULE)
+if(CONFIG_PICOLIBC AND CONFIG_PICOLIBC_MODULE)
   set(picolibc_dependency PicolibcBuild)
 endif()
 

cmake/compiler/gcc/compiler_flags.cmake

@@ -104,7 +104,7 @@ set_compiler_property(PROPERTY warning_error_coding_guideline
 set_compiler_property(PROPERTY cstd -std=)
 
 if (NOT CONFIG_NEWLIB_LIBC AND
-    NOT (CONFIG_PICOLIBC AND NOT CONFIG_PICOLIBC_USE_MODULE) AND
+    NOT (CONFIG_PICOLIBC AND NOT CONFIG_PICOLIBC_MODULE) AND
     NOT COMPILER STREQUAL "xcc" AND
     NOT CONFIG_HAS_ESPRESSIF_HAL AND
     NOT CONFIG_NATIVE_APPLICATION)

lib/libc/Kconfig

@@ -68,6 +68,12 @@ config EXTERNAL_LIBC
 
 endchoice # LIBC_IMPLEMENTATION
 
+config PICOLIBC_MODULE
+	bool "Use picolibc module"
+	default y if !CPLUSPLUS
+	help
+	  Use picolibc module instead of picolibc included with toolchain
+
 config HAS_NEWLIB_LIBC_NANO
 	bool
 

lib/libc/picolibc/CMakeLists.txt

@@ -7,7 +7,7 @@ zephyr_library_sources(libc-hooks.c)
 # used by the network stack
 zephyr_compile_definitions(__LINUX_ERRNO_EXTENSIONS__)
 
-if(NOT CONFIG_PICOLIBC_USE_MODULE)
+if(CONFIG_PICOLIBC AND NOT CONFIG_PICOLIBC_MODULE)
 
   # Use picolibc provided with the toolchain
 

lib/libc/picolibc/Kconfig

@@ -3,13 +3,6 @@
 
 if PICOLIBC
 
-config PICOLIBC_USE_MODULE
-	bool "Use picolibc module"
-	default y
-	select PICOLIBC_MODULE
-	help
-	  Use picolibc module instead of picolibc included with toolchain
-
 config PICOLIBC_HEAP_SIZE
 	int "Picolibc heap size (bytes)"
 	default 16384 if MMU
@@ -40,7 +33,14 @@ config PICOLIBC_IO_FLOAT
 	help
 	  Include floating point support in printf/scanf functions.
 
-if PICOLIBC_USE_MODULE
+if PICOLIBC_MODULE
+
+config PICOLIBC_USE_MODULE
+	bool
+	default y
+	help
+	  Hidden option that tells the picolibc module
+	  whether to build picolibc or to skip it.
 
 choice PICOLIBC_OPTIMIZATIONS
 	prompt "Optimization level"
@@ -148,6 +148,6 @@ config PICOLIBC_GLOBAL_ERRNO
 	  which can be used to avoid TLS variable usage by the library if
 	  necessary.
 
-endif # PICOLIBC_USE_MODULE
+endif # PICOLIBC_MODULE
 
 endif # PICOLIBC