Reduced ieee754 parser size (#4154)

Co-authored-by: hedger <hedger@users.noreply.github.com>

lib/SConscript

@@ -43,6 +43,7 @@ libs = env.BuildModules(
         "ble_profile",
         "bit_lib",
         "datetime",
+        "ieee754_parse_wrap",
     ],
 )
 

lib/ieee754_parse_wrap/SConscript

@@ -0,0 +1,31 @@
+Import("env")
+
+wrapped_fn_list = [
+    "strtof",
+    "strtod",
+]
+
+for wrapped_fn in wrapped_fn_list:
+    env.Append(
+        LINKFLAGS=[
+            "-Wl,--wrap," + wrapped_fn,
+        ]
+    )
+
+env.Append(
+    SDK_HEADERS=[
+        File("wrappers.h"),
+    ],
+    LINT_SOURCES=[
+        Dir("."),
+    ],
+)
+
+libenv = env.Clone(FW_LIB_NAME="ieee754_parse_wrap")
+libenv.ApplyLibFlags()
+
+sources = libenv.GlobRecursive("*.c*", ".")
+
+lib = libenv.StaticLibrary("${FW_LIB_NAME}", sources)
+libenv.Install("${LIB_DIST_DIR}", lib)
+Return("lib")

lib/ieee754_parse_wrap/wrappers.c

@@ -0,0 +1,14 @@
+#include "wrappers.h"
+
+// Based on the disassembly, providing NULL as `locale` is fine.
+// The default `strtof` and `strtod` provided in the same libc_nano also just
+// call these functions, but with an actual locale structure which was taking up
+// lots of .data space (364 bytes).
+
+float __wrap_strtof(const char* in, char** tail) {
+    return strtof_l(in, tail, NULL);
+}
+
+double __wrap_strtod(const char* in, char** tail) {
+    return strtod_l(in, tail, NULL);
+}

lib/ieee754_parse_wrap/wrappers.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stdlib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+float __wrap_strtof(const char* in, char** tail);
+double __wrap_strtod(const char* in, char** tail);
+
+#ifdef __cplusplus
+}
+#endif