cpu/esp32: workaround for static object init

cpu/esp32/Makefile

@@ -7,6 +7,10 @@ DIRS += periph
 DIRS += freertos
 DIRS += vendor
 
+ifneq (, $(filter esp_cxx, $(USEMODULE)))
+    DIRS += cxx
+endif
+
 ifneq (, $(filter esp_can, $(USEMODULE)))
     DIRS += esp-can
 endif

cpu/esp32/Makefile.include

@@ -33,6 +33,10 @@ ifneq (,$(findstring core_thread_flags,$(USEMODULE)))
     USEMODULE += pthread
 endif
 
+ifneq (,$(filter cpp,$(FEATURES_USED)))
+    USEMODULE += esp_cxx
+endif
+
 ifneq (,$(filter esp_gdbstub,$(USEMODULE)))
     USEMODULE += esp_gdb
 endif
@@ -142,6 +146,10 @@ LINKFLAGS += -T$(RIOTCPU)/$(CPU)/ld/esp32.rom.ld
 LINKFLAGS += -T$(RIOTCPU)/$(CPU)/ld/esp32.rom.nanofmt.ld
 LINKFLAGS += -nostdlib -lgcc -Wl,-gc-sections
 
+ifneq (,$(filter esp_cxx,$(USEMODULE)))
+    UNDEF += $(BINDIR)/esp_cxx/cxa_guard.o
+endif
+
 # The ELFFILE is the base one used for flashing
 FLASHFILE ?= $(ELFFILE)
 

cpu/esp32/cxx/Makefile

@@ -0,0 +1,3 @@
+MODULE=esp_cxx
+
+include $(RIOTBASE)/Makefile.base

cpu/esp32/cxx/cxa_guard.cpp

@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2018 Gunar Schorcht
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     cpu_esp32_cxx
+ * @{
+ *
+ * @file
+ * @brief       C++ functions for guarded initialization of static variables
+ *
+ * @author      Gunar Schorcht <gunar@schorcht.net>
+ *
+ * This module implements very basic versions of the glibc++ functions
+ * `__cxa_guard_acquire` and `__cxa_guard_release`. These functions operate
+ * on guard variables that are used to realize thread-safe static object
+ * initialization.
+ *
+ * The glibc++ built-in versions of these functions had to be replaced since
+ * they use the `pthread_once` function from module `pthread` for singleton
+ * objects initialization where the parameter `once` is of incompatible type.
+ *
+ * The functions implemented by this module don't use a global mutex to
+ * avoid deadlocks. Instead, within the initialization of a static variable,
+ * creating a thread that in turn tries to initialize the same static variable
+ * is not allowed and results in an abort.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <cxxabi.h>
+
+#include "assert.h"
+#include "esp_common_log.h"
+#include "irq.h"
+#include "irq_arch.h"
+#include "mutex.h"
+
+/**
+ * Structure of guard variable in glibc++
+ *  ((char*)&__guard)[0] == 1: _GLIBCXX_GUARD_BIT (static variable already initialized)
+ *  ((char*)&__guard)[1] == 1: _GLIBCXX_GUARD_PENDING_BIT (static variable is being initialized)
+ *  ((char*)&__guard)[2] == 1: _GLIBCXX_GUARD_WAITING_BIT (other thread is waiting)
+ */
+typedef struct {
+    char done;      /* initialization is already done */
+    char pending;   /* initialization is in progress */
+    char waiting;   /* another thread is waiting until initialization is finished */
+} guard_t;
+
+namespace __cxxabiv1
+{
+    extern "C"
+    int __cxa_guard_acquire (__guard *g)
+    {
+        guard_t *_gt = (guard_t *)g;
+
+        assert(_gt);
+
+        /* return if the static object is already initialized */
+        if (_gt->done) {
+          return 0;
+        }
+
+        critical_enter();
+
+        /* if another thread is already initializing the static object */
+        if (_gt->pending) {
+            critical_exit();
+            LOG_ERROR("Recursive static object initialization\n");
+            assert(0);
+        }
+
+        /* mark the initialization in process and aquire */
+        _gt->pending = 1;
+
+        critical_exit();
+        return 1;
+    }
+
+    extern "C"
+    void __cxa_guard_release (__guard *g)
+    {
+        guard_t *_gt = (guard_t *)g;
+
+        assert(_gt);
+        assert(_gt->pending);
+
+        critical_enter();
+
+        _gt->done = 1;
+        _gt->pending = 0;
+
+        critical_exit();
+    }
+
+    extern "C"
+    void __cxa_guard_abort (__guard *g)
+    {
+        guard_t *_gt = (guard_t *)g;
+
+        assert(_gt);
+        assert(_gt->pending);
+
+        _gt->pending = 0;
+    }
+}