Merge pull request #4643 from gebart/pr/clang-warning-fixes

Clang: Add support for C++

Makefile.base

@@ -66,7 +66,7 @@ $(OBJCXX): $(BINDIR)$(MODULE)/%.o: %.cpp
 	$(AD)$(CCACHE) $(CXX) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$(abspath $<))\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
-		$(CXXFLAGS) $(INCLUDES) -MD -MP -c -o $@ $(abspath $<)
+		$(CXXFLAGS) $(INCLUDES) $(CXXINCLUDES) -MD -MP -c -o $@ $(abspath $<)
 
 $(ASMOBJ): $(BINDIR)$(MODULE)/%.o: %.s
 	$(AD)$(AS) $(ASFLAGS) -o $@ $(abspath $<)

cpu/Makefile.include.llvm

@@ -1,5 +1,12 @@
 export GDBPREFIX  ?= $(PREFIX)
 export LLVMPREFIX ?= llvm-
+# Apple XCode doesn't prefix its tools with llvm-, but manually installed LLVM
+# on OSX might have the llvm- prefix, we can't simply test against uname -s.
+# Test if llvm-ar exists
+ifeq (,$(shell command -v $(LLVMPREFIX)ar 2>/dev/null))
+# fall back to system tools
+export LLVMPREFIX :=
+endif
 export CC          = clang
 export CXX         = clang++
 export LINK        = $(CC)
@@ -17,7 +24,66 @@ export DBG         = $(GDBPREFIX)gdb
 # LLVM lacks a binutils strip tool as well...
 #export STRIP      = $(LLVMPREFIX)strip
 
+# Clang on Linux uses GCC's C++ headers and libstdc++ (installed with GCC)
+# Ubuntu and Debian use /etc/alternatives/gcc-$(TARGET_ARCH)-include/c++/$(GCC_VERSION)
+# Arch uses /usr/$(TARGET_ARCH)/include/c++/$(GCC_VERSION)
+# Gentoo uses /usr/lib/gcc/$(TARGET_ARCH)/$(GCC_VERSION)/include/g++-v5
+GCC_CXX_INCLUDE_PATTERNS ?= \
+  /etc/alternatives/gcc-$(TARGET_ARCH)-include/c++/*/ \
+  /usr/$(TARGET_ARCH)/include/c++/*/ \
+  /usr/lib/gcc/$(TARGET_ARCH)/*/include/g++-v5 \
+  #
+
+# Try to find the proper multilib directory using GCC, this may fail if a cross-
+# GCC is not installed.
+ifeq ($(GCC_MULTI_DIR),)
+  GCC_MULTI_DIR := $(shell $(PREFIX)gcc -print-multi-directory $(CFLAGS) 2>/dev/null)
+endif
+
 # Tell clang to cross compile
 export CFLAGS     += -target $(TARGET_ARCH)
 export CXXFLAGS   += -target $(TARGET_ARCH)
 export LINKFLAGS  += -target $(TARGET_ARCH)
+
+# Use the wildcard Makefile function to search for existing directories matching
+# the patterns above. We use the -isystem gcc/clang argument to add the include
+# directories as system include directories, which means they will not be
+# searched until after all the project specific include directories (-I/path)
+# We sort the list of found directories and take the last one, it will likely be
+# the most recent GCC version. This avoids using old headers left over from
+# previous tool chain installations.
+GCC_CXX_INCLUDES ?= \
+    $(addprefix \
+        -isystem $(lastword $(sort \
+            $(foreach pat, $(GCC_CXX_INCLUDE_PATTERNS), $(wildcard $(pat))))), \
+        /. /$(TARGET_ARCH)/$(GCC_MULTI_DIR) /backward \
+    )
+
+# If nothing was found we will try to fall back to searching for a cross-gcc in
+# the current PATH and use a relative path for the includes
+ifeq (,$(GCC_CXX_INCLUDES))
+  GCC_CXX_INCLUDES := $(addprefix -isystem ,$(wildcard $(dir $(shell which $(PREFIX)gcc))../$(TARGET_TRIPLE)/include))
+endif
+
+# Pass the includes to the C++ compilation rule in Makefile.base
+export CXXINCLUDES += $(GCC_CXX_INCLUDES)
+
+# Some C headers (e.g. limits.h) are located with the GCC libraries
+GCC_C_INCLUDE_PATTERNS ?= \
+  /usr/lib/gcc/$(TARGET_TRIPLE)/*/ \
+  #
+
+GCC_C_INCLUDES ?= \
+    $(addprefix -isystem ,$(wildcard $(addprefix \
+        $(lastword $(sort \
+            $(foreach pat, $(GCC_C_INCLUDE_PATTERNS), $(wildcard $(pat))))), \
+        include include-fixed) \
+    ))
+
+# If nothing was found we will try to fall back to searching for the libgcc used
+# by an installed cross-GCC and use its headers.
+ifeq (,$(GCC_C_INCLUDES))
+  GCC_C_INCLUDES := $(addprefix -isystem ,$(wildcard $(addprefix $(dir $(shell $(PREFIX)gcc -print-libgcc-file-name)), include include-fixed)))
+endif
+
+export INCLUDES += $(GCC_C_INCLUDES)

sys/cpp11-compat/include/riot/mutex.hpp

@@ -44,7 +44,7 @@ class mutex {
  public:
   using native_handle_type = mutex_t*;
 
-  inline constexpr mutex() noexcept : m_mtx{0} {}
+  inline constexpr mutex() noexcept : m_mtx{{0}} {}
   ~mutex();
 
   void lock();