libstdc++-v3: include zephyr bits to support cross-compilation

This change adds a zephyr-bits.h header file which includes the
basic definitions required to support ISO C++ thread, mutex,
condition variables, and more via POSIX. For additional details
see libgcc/gthr-posix.h .

Note: this header should not be exported; it is solely for the
purpose of enabling C++ threads in the Zephyr SDK when building
against newlib or picolibc.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

libstdc++-v3/configure.ac

@@ -58,6 +58,12 @@ else
   GLIBCXX_IS_NATIVE=true
 fi
 
+case ${target} in
+  *zephyr*)
+    CXXFLAGS="$CXXFLAGS -include ${abs_top_srcdir}/include/bits/zephyr-bits.h"
+    ;;
+esac
+
 # Sets up automake.  Must come after AC_CANONICAL_SYSTEM.  Each of the
 # following is magically included in AUTOMAKE_OPTIONS in each Makefile.am.
 #  1.x:  minimum required version

libstdc++-v3/include/bits/zephyr-bits.h

@@ -0,0 +1,13 @@
+#ifndef GCC_LIBSTDCXX_V3_INCLUDE_BITS_ZEPHYR_BITS_H_
+#define GCC_LIBSTDCXX_V3_INCLUDE_BITS_ZEPHYR_BITS_H_
+
+#define _POSIX_THREADS 200809L
+#define _POSIX_TIMERS 200809L
+#define _POSIX_MONOTONIC_CLOCK 200809L
+#define _UNIX98_THREAD_MUTEX_ATTRIBUTES 1
+
+#define _PTHREAD_MUTEX_INITIALIZER (-1)
+#define _PTHREAD_COND_INITIALIZER (-1)
+#define _PTHREAD_ONCE_INIT {1,0}
+
+#endif /* GCC_LIBSTDCXX_V3_INCLUDE_BITS_ZEPHYR_BITS_H_ */