Revert back from C/C++17 to C/C++11

tensorflow/lite/micro/BUILD

@@ -405,14 +405,6 @@ tflm_cc_library(
     hdrs = ["span.h"],
 )
 
-tflm_cc_library(
-    name = "static_vector",
-    hdrs = ["static_vector.h"],
-    deps = [
-        "//tensorflow/lite/kernels:op_macros",
-    ],
-)
-
 tflm_cc_library(
     name = "system_setup",
     srcs = [

tensorflow/lite/micro/hexdump.cc

@@ -18,7 +18,6 @@
 #include <cctype>
 
 #include "tensorflow/lite/micro/debug_log.h"
-#include "tensorflow/lite/micro/static_vector.h"
 
 namespace {
 
@@ -52,15 +51,16 @@ tflite::Span<char> output(const tflite::Span<char>& buf, const char* format,
 
 }  // end anonymous namespace
 
-tflite::Span<char> tflite::hexdump(const tflite::Span<const std::byte> region,
+tflite::Span<char> tflite::hexdump(const tflite::Span<const unsigned char> region,
                                    const tflite::Span<char> out) {
   tflite::Span<char> buffer{out};
   std::size_t byte_nr = 0;
   constexpr int per_line = 16;
   const int lines = (region.size() + per_line - 1) / per_line;  // round up
 
   for (int line = 0; line < lines; ++line) {
-    tflite::StaticVector<char, per_line> ascii;
+    char ascii[per_line];
+    int ascii_nr = 0;
 
     // print address
     buffer = output(buffer, "%08X:", line);
@@ -76,7 +76,7 @@ tflite::Span<char> tflite::hexdump(const tflite::Span<const std::byte> region,
         if (std::isprint(as_int)) {
           c = static_cast<char>(as_int);
         }
-        ascii.push_back(c);
+        ascii[ascii_nr++] = c;
       } else {
         buffer = output(buffer, "   ");
       }
@@ -89,15 +89,15 @@ tflite::Span<char> tflite::hexdump(const tflite::Span<const std::byte> region,
 
     // print the ascii value
     buffer = output(buffer, "  ");
-    for (const auto& c : ascii) {
-      buffer = output(buffer, "%c", c);
+    for (int ascii_index = 0; ascii_index < ascii_nr; ascii_index++) {
+      buffer = output(buffer, "%c", ascii[ascii_index]);
     }
     buffer = output(buffer, "%c", '\n');
   }
 
   return {out.data(), out.size() - buffer.size()};
 }
 
-void tflite::hexdump(const tflite::Span<const std::byte> region) {
+void tflite::hexdump(const tflite::Span<const unsigned char> region) {
   hexdump(region, {nullptr, 0});
 }

tensorflow/lite/micro/hexdump.h

@@ -23,12 +23,12 @@ namespace tflite {
 
 // Displays the contents of a memory region, formatted in hexadecimal and ASCII
 // in a style matching Python's hexdump module, using DebugLog().
-void hexdump(Span<const std::byte> region);
+void hexdump(Span<const unsigned char> region);
 
 // Writes the contents of a memory region, formatted in hexadecimal and ASCII
 // in a style matching Python's hexdump module, to a buffer. Returns the portion
 // of the buffer written.
-Span<char> hexdump(Span<const std::byte> region, Span<char> buffer);
+Span<char> hexdump(Span<const unsigned char> region, Span<char> buffer);
 
 }  // end namespace tflite
 

tensorflow/lite/micro/tools/make/Makefile

@@ -183,7 +183,7 @@ ifeq ($(TARGET), $(HOST_OS))
 endif
 
 CXXFLAGS := \
-  -std=c++17 \
+  -std=c++11 \
   -fno-rtti \
   -fno-exceptions \
   -fno-threadsafe-statics \
@@ -192,7 +192,7 @@ CXXFLAGS := \
 
 CCFLAGS := \
   -Wimplicit-function-declaration \
-  -std=c17 \
+  -std=c11 \
   $(COMMON_FLAGS)
 
 ARFLAGS := -r
@@ -346,7 +346,6 @@ $(TENSORFLOW_ROOT)tensorflow/lite/micro/micro_time_test.cc \
 $(TENSORFLOW_ROOT)tensorflow/lite/micro/micro_utils_test.cc \
 $(TENSORFLOW_ROOT)tensorflow/lite/micro/recording_micro_allocator_test.cc \
 $(TENSORFLOW_ROOT)tensorflow/lite/micro/span_test.cc \
-$(TENSORFLOW_ROOT)tensorflow/lite/micro/static_vector_test.cc \
 $(TENSORFLOW_ROOT)tensorflow/lite/micro/arena_allocator/non_persistent_arena_buffer_allocator_test.cc \
 $(TENSORFLOW_ROOT)tensorflow/lite/micro/arena_allocator/persistent_arena_buffer_allocator_test.cc \
 $(TENSORFLOW_ROOT)tensorflow/lite/micro/arena_allocator/recording_single_arena_buffer_allocator_test.cc \

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

@@ -35,7 +35,6 @@ 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) \