common/printf: Define _POSIX_C_SOURCE when using Newlib libc

Newlib's `string.h` declares `strnlen()` function only when _GNU_SOURCE, _DEFAULT_SOURCE or _POSIX_C_SOURCE is defined. Zephyr intentionally disables POSIX declarations by defining _ANSI_SOURCE to avoid conflicts with Zephyr POSIX library and networking subsystem [1]. It's still possible to use `strnlen()` from Newlib, we just need to define _POSIX_C_SOURCE to 200809. [1] zephyrproject-rtos/zephyr#52739 BUG=b:299924239 TEST=zmake build bloonchipper Change-Id: I8cd966cd0097dfc5bf72fb9db6db6e20d96f6dee Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4973835 Commit-Queue: Patryk Duda <[email protected]> Code-Coverage: Zoss <[email protected]> Tested-by: Patryk Duda <[email protected]> Reviewed-by: Sung-Chi Li <[email protected]>
coreboot · Oct 25, 2023 · 1d859c5 · 1d859c5
1 parent 26b040b
commit 1d859c5
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/common/printf.c b/common/printf.c
@@ -5,6 +5,18 @@
 
 /* Printf-like functionality for Chrome EC */
 
+/*
+ * Define _POSIX_C_SOURCE to 200809 to unlock strnlen() when using Newlib
+ * libc. Newlib's CMakeLists.txt file intentionally disables POSIX definitions
+ * from Newlib to avoid conflicts with Zephyr POSIX library and networking
+ * subsystem.
+ *
+ * Refer to the Zephyr's Github issue #52739 for more details.
+ */
+#ifdef CONFIG_NEWLIB_LIBC
+#define _POSIX_C_SOURCE 200809
+#endif /* CONFIG_NEWLIB_LIBC */
+
 #include "builtin/assert.h"
 #include "console.h"
 #include "printf.h"