cmake: toolchain: cross_compile: check newlib and picolibc

Add support to check whether Cross Compile toolchain support newlib and
picolibc or not.

Signed-off-by: Jiafei Pan <[email protected]>

Author: JiafeiPan

cmake/toolchain/cross-compile/generic.cmake

@@ -21,11 +21,41 @@ if((NOT (DEFINED CROSS_COMPILE)) AND (DEFINED ENV{CROSS_COMPILE}))
   set(CROSS_COMPILE $ENV{CROSS_COMPILE})
 endif()
 
+if((NOT (DEFINED CROSS_COMPILE_TOOLCHAIN_PATH)) AND (DEFINED ENV{CROSS_COMPILE_TOOLCHAIN_PATH}))
+  set(CROSS_COMPILE_TOOLCHAIN_PATH $ENV{CROSS_COMPILE_TOOLCHAIN_PATH})
+endif()
+
 set(   CROSS_COMPILE ${CROSS_COMPILE} CACHE PATH "")
 assert(CROSS_COMPILE "CROSS_COMPILE is not set")
 
+set(CROSS_COMPILE_TOOLCHAIN_PATH ${CROSS_COMPILE_TOOLCHAIN_PATH} CACHE PATH "Cross Compile toolchain directory")
+
 set(COMPILER gcc)
 set(LINKER ld)
 set(BINTOOLS gnu)
 
+# CROSS_COMPILE is flexible, meaning that it can in principle always support newlib or picolibc.
+# This is not decided by CROSS_COMPILE itself, but depends on libraries distributed with  the installation.
+# Also newlib or picolibc may be created as add-ons. Thus always stating that CROSS_COMPILE does not have
+# newlib or picolibc would be wrong. Same with stating that CROSS_COMPILE has newlib or Picolibc.
+# The best assumption for TOOLCHAIN_HAS_<NEWLIB|PICOLIBC> is to check for the  presence of
+# '_newlib_version.h' / 'picolibc' and have the default value set accordingly.
+# This provides a best effort mechanism to allow developers to have the newlib C / Picolibc library
+# selection available in Kconfig.
+# Developers can manually indicate library support with '-DTOOLCHAIN_HAS_<NEWLIB|PICOLIBC>=<ON|OFF>'
+
+# Support for newlib is indicated by the presence of '_newlib_version.h' in the toolchain path.
+if(NOT CROSS_COMPILE_TOOLCHAIN_PATH STREQUAL "")
+  file(GLOB_RECURSE newlib_header ${CROSS_COMPILE_TOOLCHAIN_PATH}/_newlib_version.h)
+  if(newlib_header)
+    set(TOOLCHAIN_HAS_NEWLIB ON CACHE BOOL "True if toolchain supports newlib")
+  endif()
+
+  # Support for picolibc is indicated by the presence of 'picolibc.h' in the toolchain path.
+  file(GLOB_RECURSE picolibc_header ${CROSS_COMPILE_TOOLCHAIN_PATH}/picolibc.h)
+  if(picolibc_header)
+    set(TOOLCHAIN_HAS_PICOLIBC ON CACHE BOOL "True if toolchain supports picolibc")
+  endif()
+endif()
+
 message(STATUS "Found toolchain: cross-compile (${CROSS_COMPILE})")