libc: Move strnlen into common

Move the strnlen implementation into common so its available to any
libc that may not implement strnlen.

Signed-off-by: Kumar Gala <kumar.gala@intel.com>

Author: galak

cmake/toolchain/armclang/Kconfig

@@ -15,6 +15,7 @@ choice LIBC_IMPLEMENTATION
 
 config ARMCLANG_STD_LIBC
 	bool "ARM Compiler C library"
+	select COMMON_LIBC_STRNLEN
 	select COMMON_LIBC_TIME if POSIX_CLOCK
 	help
 	  Use the full Arm Compiler runtime libraries.

lib/libc/Kconfig

@@ -65,6 +65,7 @@ config MINIMAL_LIBC
 	depends on !REQUIRES_FULL_LIBC
 	depends on MINIMAL_LIBC_SUPPORTED
 	imply COMPILER_FREESTANDING
+	select COMMON_LIBC_STRNLEN
 	help
 	  Build with minimal C library.
 

lib/libc/armstdc/CMakeLists.txt

@@ -2,7 +2,6 @@
 
 zephyr_library()
 zephyr_library_sources(src/errno.c)
-zephyr_library_sources(src/string.c)
 zephyr_library_sources(src/libc-hooks.c)
 zephyr_library_sources_ifndef(CONFIG_MULTITHREADING src/threading_weak.c)
 

lib/libc/common/CMakeLists.txt

@@ -4,3 +4,4 @@ zephyr_library()
 zephyr_library_property(ALLOW_EMPTY TRUE)
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_TIME source/time/time.c)
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_MALLOC source/stdlib/malloc.c)
+zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_STRNLEN source/string/strnlen.c)

lib/libc/common/Kconfig

@@ -37,3 +37,8 @@ config COMMON_LIBC_REALLOCARRAY
 	help
 	  Enable the common C library trivial implementation of
 	  reallocarray, which forwards to realloc.
+
+config COMMON_LIBC_STRNLEN
+	bool
+	help
+	  common implementation of strnlen().

lib/libc/armstdc/src/string.c lib/libc/common/source/string/strnlen.c

@@ -116,25 +116,6 @@ size_t strlen(const char *s)
 	return n;
 }
 
-/**
- *
- * @brief Get fixed-size string length
- *
- * @return number of bytes in fixed-size string <s>
- */
-
-size_t strnlen(const char *s, size_t maxlen)
-{
-	size_t n = 0;
-
-	while (*s != '\0' && n < maxlen) {
-		s++;
-		n++;
-	}
-
-	return n;
-}
-
 /**
  *
  * @brief Compare two strings