Fix minor warnings.

When compiling with -Wall/-Werror, several warnings related to signed/unsigned
comparison and an incorrect format string kill the build. Additionally, when
compiling under GCC 4.8.x, `max_align_t` is not a member of `std`. This change
fixes these minor errors.

PiperOrigin-RevId: 284216526
Change-Id: I05b6e76a626dc01da9400772ba0fbda2bb6b5b63

tensorflow/lite/experimental/micro/micro_allocator.cc

@@ -42,6 +42,19 @@ struct TensorInfo {
 // requirement for SIMD extensions.
 constexpr int kBufferAlignment = 16;
 
+// If building with GNU clib from GCC 4.8.x or lower, `max_align_t` is not a
+// member of `std`. If using a newer version of clib, we import `max_align_t`
+// into the local anonymous namespace to be able to use it like the global
+// `max_align_t` from the older clib.
+#if defined(__GNUC__) && defined(__GNUC_PREREQ)
+#if __GNUC_PREREQ(4, 9)
+using std::max_align_t;
+#endif
+#else
+// We assume other compiler/clib configurations don't have this issue.
+using std::max_align_t;
+#endif
+
 class MicroBuiltinDataAllocator : public BuiltinDataAllocator {
  public:
   explicit MicroBuiltinDataAllocator(SimpleMemoryAllocator* memory_allocator)
@@ -51,7 +64,7 @@ class MicroBuiltinDataAllocator : public BuiltinDataAllocator {
     // Align to an address that is proper for all primitive types, but no more
     // than the size.
     return memory_allocator_->AllocateFromTail(
-        size, std::min(size, alignof(std::max_align_t)));
+        size, std::min(size, alignof(max_align_t)));
   }
   void Deallocate(void* data) override {
     // Do not deallocate, builtin data needs to be available for the life time
@@ -412,7 +425,7 @@ TfLiteStatus MicroAllocator::InitializeRuntimeTensor(
     // If we've found a buffer, does it have any data?
     if (auto* array = buffer->data()) {
       // If it has any data, is the data size larger than zero?
-      if (size_t array_size = array->size()) {
+      if (array->size()) {
         // We've found a buffer with valid data, so update the runtime tensor
         // data structure to point to it.
         result->data.raw =

tensorflow/lite/experimental/micro/micro_interpreter.cc

@@ -21,7 +21,7 @@ limitations under the License.
 
 namespace tflite {
 namespace {
-const int kStackDataAllocatorSize = 128;
+const size_t kStackDataAllocatorSize = 128;
 class StackDataAllocator : public BuiltinDataAllocator {
  public:
   void* Allocate(size_t size) override {
@@ -91,7 +91,7 @@ MicroInterpreter::MicroInterpreter(const Model* model,
   // NOTE: This requires that the flatbuffer is held in memory which can be
   // modified by this process.
   if (!FLATBUFFERS_LITTLEENDIAN) {
-    for (int t = 0; t < tensors_size(); ++t) {
+    for (size_t t = 0; t < tensors_size(); ++t) {
       TfLiteTensor* thisTensor = &context_.tensors[t];
       if (thisTensor->allocation_type == kTfLiteMmapRo)
         CorrectTensorEndianness(thisTensor);

tensorflow/lite/experimental/micro/micro_optional_debug_tools.cc

@@ -14,6 +14,13 @@ limitations under the License.
 ==============================================================================*/
 #include "tensorflow/lite/experimental/micro/micro_optional_debug_tools.h"
 
+// `cinttypes` requires `__STDC_FORMAT_MACROS` to be defined to expose `PRId32`.
+#ifndef __STDC_FORMAT_MACROS
+#define __STDC_FORMAT_MACROS
+#endif
+
+#include <cinttypes>
+
 #include "tensorflow/lite/schema/schema_generated.h"
 namespace tflite {
 namespace {
@@ -122,7 +129,7 @@ void PrintInterpreterState(MicroInterpreter* interpreter) {
       printf("Node %3zu Operator Custom Name %s\n", node_index,
              reg->custom_name);
     } else {
-      printf("Node %3zu Operator Builtin Code %3d %s\n", node_index,
+      printf("Node %3zu Operator Builtin Code %3" PRId32 " %s\n", node_index,
              reg->builtin_code, EnumNamesBuiltinOperator()[reg->builtin_code]);
     }
     printf("  Inputs:");

tensorflow/lite/experimental/micro/test_helpers.cc

@@ -47,7 +47,7 @@ class StackAllocator : public flatbuffers::Allocator {
     return *inst;
   }
 
-  static constexpr int kStackAllocatorSize = 4096;
+  static constexpr size_t kStackAllocatorSize = 4096;
 
  private:
   uint8_t data_backing_[kStackAllocatorSize];