build: begin using -std=c++17 and c17 in Makefile builds (#2648)

Begin using -std=c++17 and -std=c17 in Makefile builds on
all platforms. Bazel builds have been using C++17 since 52c9568.

Set `-stdlib=libc++ on xt-clang` on Xtensa to add C++17 library
support in addition to compiler support. From the xt-clang docs:

    Starting with the RI-2019.1 release, XT-CLANG has included support
    for C++14 and C++17 language features. The compiler support for
    C++14 and C++17 is accompanied by the C++ library from the LLVM
    project. This library can be selected with the -stdlib=libc++
    option, and this is strongly recommended when compiling with
    -std=c++14 or - std=c++17. Starting with the RI-2021.6 release, two
    additional versions of this C++ library are provided— one that
    excludes support for exception handling, and one that excludes both
    exception handling and run-time type identification. These libraries
    can be selected with -stdlib=libc ++-e and -stdlib=libc++-re options
    respectively.

Based on the `docker run` command in
tflite-micro/.github/workflows/xtensa_presubmit.yml, our CI is
currently using RI-2020.4.

Refactor the make/ext_libs/xtensa_download.sh script to make it eaiser
to patch downloads for all Xtensa platforms. The old script made overly
strict assumptions about the name of the patch.

Patch the Xtensa vision_p6 platform download xi_tflmlib_vision_p6 for
compatibility with the C++ library standard. Use the header <climits> to
access constants such as INT_MAX.

BUG=#2650

tensorflow/lite/micro/docs/new_platform_support.md

@@ -25,7 +25,7 @@ hardware to run inference on TfLite models.
 Prior to integrating TFLM with a specific hardware involves tasks that is
 outside the scope of the TFLM project, including:
 
- * Toolchain setup - TFLM requires support for C++11
+ * Toolchain setup - TFLM requires support for C++17
  * Set up and installation of board-specific SDKs and IDEs
  * Compiler flags and Linker setup
  * Integrating peripherals such as cameras, microphones and accelerometers to

tensorflow/lite/micro/tools/make/Makefile

@@ -182,7 +182,7 @@ ifeq ($(TARGET), $(HOST_OS))
 endif
 
 CXXFLAGS := \
-  -std=c++11 \
+  -std=c++17 \
   -fno-rtti \
   -fno-exceptions \
   -fno-threadsafe-statics \
@@ -191,7 +191,7 @@ CXXFLAGS := \
 
 CCFLAGS := \
   -Wimplicit-function-declaration \
-  -std=c11 \
+  -std=c17 \
   $(COMMON_FLAGS)
 
 ARFLAGS := -r
@@ -257,13 +257,6 @@ else ifeq ($(BUILD_TYPE), no_tf_lite_static_memory)
 	# https://github.com/tensorflow/tensorflow/issues/43076
 	CXXFLAGS := $(filter-out -DTF_LITE_STATIC_MEMORY, $(CXXFLAGS))
 	CCFLAGS := $(filter-out -DTF_LITE_STATIC_MEMORY, $(CCFLAGS))
-
-	# We are using C++17 for the no_tf_lite_static_memory_build to make it close
-	# to the TfLite bazel build.
-	CXXFLAGS := $(filter-out -std=c++11, $(CXXFLAGS))
-	CXXFLAGS += -std=c++17
-	CCFLAGS := $(filter-out -std=c11, $(CCLAGS))
-	CCFLAGS += -std=c17
 endif
 
 # This library is the main target for this makefile. It will contain a minimal

tensorflow/lite/micro/tools/make/ext_libs/xi_tflmlib_vision_p6.patch

@@ -0,0 +1,28 @@
+From ed92529a6be7a910462558edcf10070fbb0f2870 Mon Sep 17 00:00:00 2001
+From: Ryan Kuester <kuester@bdti.com>
+Date: Thu, 1 Aug 2024 12:48:12 -0500
+Subject: [PATCH] fix: use <climits> instead of <limits> to access INT_MAX and
+ friends
+
+For compatibility with the C++ library standard, use the header,
+<climits>, to access constants such as INT_MAX.
+---
+ runtime/include/cnnrt_xi.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/runtime/include/cnnrt_xi.h b/runtime/include/cnnrt_xi.h
+index f3a911e..00c74b8 100644
+--- a/runtime/include/cnnrt_xi.h
++++ b/runtime/include/cnnrt_xi.h
+@@ -25,7 +25,7 @@
+ #  define INCLUDE_XI_CNN
+ #endif
+
+-#include <limits>
++#include <climits>
+ #include "xi_api.h"
+ #include "xi_cnn_api.h"
+ #include "xi_tile_manager.h"
+-- 
+2.43.0
+

tensorflow/lite/micro/tools/make/ext_libs/xtensa_download.sh

@@ -38,11 +38,17 @@ set -e
 source ${3}tensorflow/lite/micro/tools/make/bash_helpers.sh
 
 DOWNLOADS_DIR=${1}
+PATCH=""
 
-if [[ ${2} == "hifi4" || ${2} == "hifi3" ]]; then
+if [[ ${2} == "hifi3" ]]; then
   LIBRARY_URL="http://github.com/foss-xtensa/nnlib-hifi4/raw/master/archive/xa_nnlib_hifi4_09_05_2023.zip"
   LIBRARY_DIRNAME="xa_nnlib_hifi4"
   LIBRARY_MD5="2a54e056aef73a4fcffde4643998501a"
+elif [[ ${2} == "hifi4" ]]; then
+  LIBRARY_URL="http://github.com/foss-xtensa/nnlib-hifi4/raw/master/archive/xa_nnlib_hifi4_09_05_2023.zip"
+  LIBRARY_DIRNAME="xa_nnlib_hifi4"
+  LIBRARY_MD5="2a54e056aef73a4fcffde4643998501a"
+  PATCH="../../ext_libs/xa_nnlib_hifi4.patch"
 elif [[ ${2} == "hifi5" ]]; then
   LIBRARY_URL="http://github.com/foss-xtensa/nnlib-hifi5/raw/master/archive/xa_nnlib_hifi5_09_05_2023.zip"
   LIBRARY_DIRNAME="xa_nnlib_hifi5"
@@ -51,6 +57,7 @@ elif [[ ${2} == "vision_p6" ]]; then
   LIBRARY_URL="https://github.com/foss-xtensa/tflmlib_vision/raw/main/archive/xi_tflmlib_vision_p6_22_06_29.zip"
   LIBRARY_DIRNAME="xi_tflmlib_vision_p6"
   LIBRARY_MD5="fea3720d76fdb3a5a337ace7b6081b56"
+  PATCH="../../ext_libs/xi_tflmlib_vision_p6.patch"
 else
   echo "Attempting to download an unsupported xtensa variant: ${2}"
   exit 1
@@ -79,9 +86,9 @@ else
 
   pushd "${LIBRARY_INSTALL_PATH}" > /dev/null
   chmod -R +w ./
-  if [[ -f "../../ext_libs/xa_nnlib_${2}.patch" ]]; then
+  if [ "${PATCH}" ]; then
     create_git_repo ./
-    apply_patch_to_folder ./ "../../ext_libs/xa_nnlib_${2}.patch" "TFLM patch"
+    apply_patch_to_folder ./ ${PATCH} "TFLM patch"
   fi
 fi
 

tensorflow/lite/micro/tools/make/targets/arc/arc_common.inc

@@ -64,9 +64,6 @@ ifneq ($(LCF_FILE), )
   PLATFORM_LDFLAGS += $(notdir $(LCF_FILE))
 endif
 
-  CXXFLAGS := $(filter-out -std=c++11,$(CXXFLAGS))
-  CCFLAGS := $(filter-out -std=c11,$(CCFLAGS))
-
   ldflags_to_remove = -Wl,--fatal-warnings -Wl,--gc-sections
   LDFLAGS := $(filter-out $(ldflags_to_remove),$(LDFLAGS))
 

tensorflow/lite/micro/tools/make/targets/ceva_makefile.inc

@@ -33,8 +33,8 @@ $(TARGET_ARCH_DEFINES) \
 	-D_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY=""
 
 
-CXXFLAGS := -std=c++11 -DTF_LITE_STATIC_MEMORY 
-CCFLAGS  := -std=c11   -DTF_LITE_STATIC_MEMORY 
+CXXFLAGS := -std=c++17 -DTF_LITE_STATIC_MEMORY 
+CCFLAGS  := -std=c17   -DTF_LITE_STATIC_MEMORY 
 
 ifeq ($(TARGET_ARCH), CEVA_BX1)
 PLATFORM_FLAGS += \

tensorflow/lite/micro/tools/make/targets/xtensa_makefile.inc

@@ -35,6 +35,7 @@ endif
 TARGET_ARCH_DEFINES := -D$(shell echo $(TARGET_ARCH) | tr [a-z] [A-Z])
 
 PLATFORM_FLAGS = \
+  -stdlib=libc++ \
   -DTF_LITE_MCU_DEBUG_LOG \
   -DTF_LITE_USE_CTIME \
   --xtensa-core=$(XTENSA_CORE) \

tensorflow/lite/micro/tools/project_generation/Makefile

@@ -72,14 +72,14 @@ ifeq ($(BUILD_TYPE), cmsis_nn)
 endif
 
 CXXFLAGS := \
-  -std=c++11 \
+  -std=c++17 \
   -fno-rtti \
   -fno-exceptions \
   -fno-threadsafe-statics \
   $(COMMON_FLAGS)
 
 CCFLAGS := \
-  -std=c11 \
+  -std=c17 \
   $(COMMON_FLAGS)
 
 ARFLAGS := -r