Fix "unsafe narrowing" warnings in absl, 5/n.

Addresses failures with the following, in some files:
-Wshorten-64-to-32
-Wimplicit-int-conversion
-Wsign-compare
-Wsign-conversion
-Wtautological-unsigned-zero-compare

(This specific CL focuses on .cc files in strings/internal/.)

Bug: chromium:1292951
PiperOrigin-RevId: 468215101
Change-Id: I07fa487bcf2cf62d403489c3be7a5997cdef8987

14 files changed, 283 insertions, 233 deletions

diff --git a/absl/strings/internal/charconv_bigint.cc b/absl/strings/internal/charconv_bigint.cc
index ebf8c079..282b639e 100644
--- a/absl/strings/internal/charconv_bigint.cc
+++ b/absl/strings/internal/charconv_bigint.cc
@@ -242,7 +242,7 @@ int BigUnsigned<max_words>::ReadDigits(const char* begin, const char* end,
       // decimal exponent to compensate.
       --exponent_adjust;
     }
-    int digit = (*begin - '0');
+    char digit = (*begin - '0');
     --significant_digits;
     if (significant_digits == 0 && std::next(begin) != end &&
         (digit == 0 || digit == 5)) {
@@ -255,7 +255,7 @@ int BigUnsigned<max_words>::ReadDigits(const char* begin, const char* end,
       // 500000...000000000001 to correctly round up, rather than to nearest.
       ++digit;
     }
-    queued = 10 * queued + digit;
+    queued = 10 * queued + static_cast<uint32_t>(digit);
     ++digits_queued;
     if (digits_queued == kMaxSmallPowerOfTen) {
       MultiplyBy(kTenToNth[kMaxSmallPowerOfTen]);
@@ -341,8 +341,8 @@ std::string BigUnsigned<max_words>::ToString() const {
   std::string result;
   // Build result in reverse order
   while (copy.size() > 0) {
-    int next_digit = copy.DivMod<10>();
-    result.push_back('0' + next_digit);
+    uint32_t next_digit = copy.DivMod<10>();
+    result.push_back('0' + static_cast<char>(next_digit));
   }
   if (result.empty()) {
     result.push_back('0');
diff --git a/absl/strings/internal/charconv_parse.cc b/absl/strings/internal/charconv_parse.cc
index d29acaf4..98823def 100644
--- a/absl/strings/internal/charconv_parse.cc
+++ b/absl/strings/internal/charconv_parse.cc
@@ -190,11 +190,11 @@ bool IsDigit<16>(char ch) {
 
 template <>
 unsigned ToDigit<10>(char ch) {
-  return ch - '0';
+  return static_cast<unsigned>(ch - '0');
 }
 template <>
 unsigned ToDigit<16>(char ch) {
-  return kAsciiToInt[static_cast<unsigned char>(ch)];
+  return static_cast<unsigned>(kAsciiToInt[static_cast<unsigned char>(ch)]);
 }
 
 template <>
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index 29954112..601457ee 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -129,8 +129,9 @@ class RefcountAndFlags {
   }
 
   // Returns the current reference count using acquire semantics.
-  inline int32_t Get() const {
-    return count_.load(std::memory_order_acquire) >> kNumFlags;
+  inline size_t Get() const {
+    return static_cast<size_t>(count_.load(std::memory_order_acquire) >>
+                               kNumFlags);
   }
 
   // Returns whether the atomic integer is 1.
diff --git a/absl/strings/internal/cord_rep_btree.cc b/absl/strings/internal/cord_rep_btree.cc
index cacbf3da..7ce36128 100644
--- a/absl/strings/internal/cord_rep_btree.cc
+++ b/absl/strings/internal/cord_rep_btree.cc
@@ -17,6 +17,7 @@
 #include <cassert>
 #include <cstdint>
 #include <iostream>
+#include <ostream>
 #include <string>
 
 #include "absl/base/attributes.h"
@@ -55,8 +56,10 @@ inline bool exhaustive_validation() {
 // Prints the entire tree structure or 'rep'. External callers should
 // not specify 'depth' and leave it to its default (0) value.
 // Rep may be a CordRepBtree tree, or a SUBSTRING / EXTERNAL / FLAT node.
-void DumpAll(const CordRep* rep, bool include_contents, std::ostream& stream,
-             int depth = 0) {
+void DumpAll(const CordRep* rep,
+             bool include_contents,
+             std::ostream& stream,
+             size_t depth = 0) {
   // Allow for full height trees + substring -> flat / external nodes.
   assert(depth <= CordRepBtree::kMaxDepth + 2);
   std::string sharing = const_cast<CordRep*>(rep)->refcount.IsOne()
diff --git a/absl/strings/internal/cord_rep_btree.h b/absl/strings/internal/cord_rep_btree.h
index 2cbc09ec..eed5609e 100644
--- a/absl/strings/internal/cord_rep_btree.h
+++ b/absl/strings/internal/cord_rep_btree.h
@@ -95,8 +95,9 @@ class CordRepBtree : public CordRep {
   // local stack variable compared to Cord's current near 400 bytes stack use.
   // The maximum `height` value of a node is then `kMaxDepth - 1` as node height
   // values start with a value of 0 for leaf nodes.
-  static constexpr int kMaxDepth = 12;
-  static constexpr int kMaxHeight = kMaxDepth - 1;
+  static constexpr size_t kMaxDepth = 12;
+  // See comments on height() for why this is an int and not a size_t.
+  static constexpr int kMaxHeight = static_cast<int>(kMaxDepth - 1);
 
   // `Action` defines the action for unwinding changes done at the btree's leaf
   // level that need to be propagated up to the parent node(s). Each operation
diff --git a/absl/strings/internal/cord_rep_btree_navigator.cc b/absl/strings/internal/cord_rep_btree_navigator.cc
index 9b896a3d..6ed20c23 100644
--- a/absl/strings/internal/cord_rep_btree_navigator.cc
+++ b/absl/strings/internal/cord_rep_btree_navigator.cc
@@ -90,7 +90,7 @@ CordRepBtreeNavigator::Position CordRepBtreeNavigator::Skip(size_t n) {
   // edges that must be skipped.
   while (height > 0) {
     node = edge->btree();
-    index_[height] = index;
+    index_[height] = static_cast<uint8_t>(index);
     node_[--height] = node;
     index = node->begin();
     edge = node->Edge(index);
@@ -101,7 +101,7 @@ CordRepBtreeNavigator::Position CordRepBtreeNavigator::Skip(size_t n) {
       edge = node->Edge(index);
     }
   }
-  index_[0] = index;
+  index_[0] = static_cast<uint8_t>(index);
   return {edge, n};
 }
 
@@ -126,7 +126,7 @@ ReadResult CordRepBtreeNavigator::Read(size_t edge_offset, size_t n) {
   do {
     length -= edge->length;
     while (++index == node->end()) {
-      index_[height] = index;
+      index_[height] = static_cast<uint8_t>(index);
       if (++height > height_) {
         subtree->set_end(subtree_end);
         if (length == 0) return {subtree, 0};
@@ -154,7 +154,7 @@ ReadResult CordRepBtreeNavigator::Read(size_t edge_offset, size_t n) {
   // edges that must be read, adding 'down' nodes to `subtree`.
   while (height > 0) {
     node = edge->btree();
-    index_[height] = index;
+    index_[height] = static_cast<uint8_t>(index);
     node_[--height] = node;
     index = node->begin();
     edge = node->Edge(index);
@@ -178,7 +178,7 @@ ReadResult CordRepBtreeNavigator::Read(size_t edge_offset, size_t n) {
     subtree->edges_[subtree_end++] = Substring(edge, 0, length);
   }
   subtree->set_end(subtree_end);
-  index_[0] = index;
+  index_[0] = static_cast<uint8_t>(index);
   return {tree, length};
 }
 
diff --git a/absl/strings/internal/cordz_info.cc b/absl/strings/internal/cordz_info.cc
index dac3fd8b..530f33be 100644
--- a/absl/strings/internal/cordz_info.cc
+++ b/absl/strings/internal/cordz_info.cc
@@ -35,7 +35,7 @@ namespace cord_internal {
 using ::absl::base_internal::SpinLockHolder;
 
 #ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
-constexpr int CordzInfo::kMaxStackDepth;
+constexpr size_t CordzInfo::kMaxStackDepth;
 #endif
 
 ABSL_CONST_INIT CordzInfo::List CordzInfo::global_list_{absl::kConstInit};
@@ -291,7 +291,7 @@ CordzInfo::MethodIdentifier CordzInfo::GetParentMethod(const CordzInfo* src) {
                                                            : src->method_;
 }
 
-int CordzInfo::FillParentStack(const CordzInfo* src, void** stack) {
+size_t CordzInfo::FillParentStack(const CordzInfo* src, void** stack) {
   assert(stack);
   if (src == nullptr) return 0;
   if (src->parent_stack_depth_) {
@@ -302,11 +302,14 @@ int CordzInfo::FillParentStack(const CordzInfo* src, void** stack) {
   return src->stack_depth_;
 }
 
-CordzInfo::CordzInfo(CordRep* rep, const CordzInfo* src,
+CordzInfo::CordzInfo(CordRep* rep,
+                     const CordzInfo* src,
                      MethodIdentifier method)
     : rep_(rep),
-      stack_depth_(absl::GetStackTrace(stack_, /*max_depth=*/kMaxStackDepth,
-                                       /*skip_count=*/1)),
+      stack_depth_(
+          static_cast<size_t>(absl::GetStackTrace(stack_,
+                                                  /*max_depth=*/kMaxStackDepth,
+                                                  /*skip_count=*/1))),
       parent_stack_depth_(FillParentStack(src, parent_stack_)),
       method_(method),
       parent_method_(GetParentMethod(src)),
diff --git a/absl/strings/internal/cordz_info.h b/absl/strings/internal/cordz_info.h
index 026d5b99..8e86f223 100644
--- a/absl/strings/internal/cordz_info.h
+++ b/absl/strings/internal/cordz_info.h
@@ -196,7 +196,7 @@ class ABSL_LOCKABLE CordzInfo : public CordzHandle {
     std::atomic<CordzInfo*> head ABSL_GUARDED_BY(mutex){nullptr};
   };
 
-  static constexpr int kMaxStackDepth = 64;
+  static constexpr size_t kMaxStackDepth = 64;
 
   explicit CordzInfo(CordRep* rep, const CordzInfo* src,
                      MethodIdentifier method);
@@ -216,7 +216,7 @@ class ABSL_LOCKABLE CordzInfo : public CordzHandle {
   // `stack_` depending on `parent_stack_` being empty, returning the size of
   // the parent stack.
   // Returns 0 if `src` is null.
-  static int FillParentStack(const CordzInfo* src, void** stack);
+  static size_t FillParentStack(const CordzInfo* src, void** stack);
 
   void ODRCheck() const {
 #ifndef NDEBUG
@@ -244,8 +244,8 @@ class ABSL_LOCKABLE CordzInfo : public CordzHandle {
 
   void* stack_[kMaxStackDepth];
   void* parent_stack_[kMaxStackDepth];
-  const int stack_depth_;
-  const int parent_stack_depth_;
+  const size_t stack_depth_;
+  const size_t parent_stack_depth_;
   const MethodIdentifier method_;
   const MethodIdentifier parent_method_;
   CordzUpdateTracker update_tracker_;
diff --git a/absl/strings/internal/cordz_statistics.h b/absl/strings/internal/cordz_statistics.h
index 57071905..9f558df4 100644
--- a/absl/strings/internal/cordz_statistics.h
+++ b/absl/strings/internal/cordz_statistics.h
@@ -45,12 +45,12 @@ struct CordzStatistics {
   };
 
   // The size of the cord in bytes. This matches the result of Cord::size().
-  int64_t size = 0;
+  size_t size = 0;
 
   // The estimated memory used by the sampled cord. This value matches the
   // value as reported by Cord::EstimatedMemoryUsage().
   // A value of 0 implies the property has not been recorded.
-  int64_t estimated_memory_usage = 0;
+  size_t estimated_memory_usage = 0;
 
   // The effective memory used by the sampled cord, inversely weighted by the
   // effective indegree of each allocated node. This is a representation of the
@@ -59,14 +59,14 @@ struct CordzStatistics {
   // by multiple Cord instances, and for cases where a Cord includes the same
   // node multiple times (either directly or indirectly).
   // A value of 0 implies the property has not been recorded.
-  int64_t estimated_fair_share_memory_usage = 0;
+  size_t estimated_fair_share_memory_usage = 0;
 
   // The total number of nodes referenced by this cord.
   // For ring buffer Cords, this includes the 'ring buffer' node.
   // For btree Cords, this includes all 'CordRepBtree' tree nodes as well as all
   // the substring, flat and external nodes referenced by the tree.
   // A value of 0 implies the property has not been recorded.
-  int64_t node_count = 0;
+  size_t node_count = 0;
 
   // Detailed node counts per type
   NodeCounts node_counts;
diff --git a/absl/strings/internal/memutil.cc b/absl/strings/internal/memutil.cc
index 2519c688..44996a75 100644
--- a/absl/strings/internal/memutil.cc
+++ b/absl/strings/internal/memutil.cc
@@ -54,10 +54,11 @@ size_t memspn(const char* s, size_t slen, const char* accept) {
 
 cont:
   c = *p++;
-  if (slen-- == 0) return p - 1 - s;
+  if (slen-- == 0)
+    return static_cast<size_t>(p - 1 - s);
   for (spanp = accept; (sc = *spanp++) != '\0';)
     if (sc == c) goto cont;
-  return p - 1 - s;
+  return static_cast<size_t>(p - 1 - s);
 }
 
 size_t memcspn(const char* s, size_t slen, const char* reject) {
@@ -68,9 +69,10 @@ size_t memcspn(const char* s, size_t slen, const char* reject) {
   while (slen-- != 0) {
     c = *p++;
     for (spanp = reject; (sc = *spanp++) != '\0';)
-      if (sc == c) return p - 1 - s;
+      if (sc == c)
+        return static_cast<size_t>(p - 1 - s);
   }
-  return p - s;
+  return static_cast<size_t>(p - s);
 }
 
 char* mempbrk(const char* s, size_t slen, const char* accept) {
@@ -97,8 +99,9 @@ const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
   const char* hayend = phaystack + haylen - neelen + 1;
   // A static cast is used here to work around the fact that memchr returns
   // a void* on Posix-compliant systems and const void* on Windows.
-  while ((match = static_cast<const char*>(
-              memchr(phaystack, pneedle[0], hayend - phaystack)))) {
+  while (
+      (match = static_cast<const char*>(memchr(
+           phaystack, pneedle[0], static_cast<size_t>(hayend - phaystack))))) {
     if (memcmp(match, pneedle, neelen) == 0)
       return match;
     else
diff --git a/absl/strings/internal/str_format/arg.cc b/absl/strings/internal/str_format/arg.cc
index 02aeeebe..007e8e83 100644
--- a/absl/strings/internal/str_format/arg.cc
+++ b/absl/strings/internal/str_format/arg.cc
@@ -77,7 +77,7 @@ class IntDigits {
       v >>= 3;
     } while (v);
     start_ = p;
-    size_ = storage_ + sizeof(storage_) - p;
+    size_ = static_cast<size_t>(storage_ + sizeof(storage_) - p);
   }
 
   // Print the signed or unsigned integer as decimal.
@@ -86,7 +86,8 @@ class IntDigits {
   void PrintAsDec(T v) {
     static_assert(std::is_integral<T>::value, "");
     start_ = storage_;
-    size_ = numbers_internal::FastIntToBuffer(v, storage_) - storage_;
+    size_ = static_cast<size_t>(numbers_internal::FastIntToBuffer(v, storage_) -
+                                storage_);
   }
 
   void PrintAsDec(int128 v) {
@@ -115,7 +116,7 @@ class IntDigits {
     if (add_neg) {
       *--p = '-';
     }
-    size_ = storage_ + sizeof(storage_) - p;
+    size_ = static_cast<size_t>(storage_ + sizeof(storage_) - p);
     start_ = p;
   }
 
@@ -138,7 +139,7 @@ class IntDigits {
       ++p;
     }
     start_ = p;
-    size_ = storage_ + sizeof(storage_) - p;
+    size_ = static_cast<size_t>(storage_ + sizeof(storage_) - p);
   }
 
   // Print the unsigned integer as hex using uppercase.
@@ -154,7 +155,7 @@ class IntDigits {
       v >>= 4;
     } while (v);
     start_ = p;
-    size_ = storage_ + sizeof(storage_) - p;
+    size_ = static_cast<size_t>(storage_ + sizeof(storage_) - p);
   }
 
   // The printed value including the '-' sign if available.
@@ -208,10 +209,12 @@ string_view SignColumn(bool neg, const FormatConversionSpecImpl conv) {
   return {};
 }
 
-bool ConvertCharImpl(unsigned char v, const FormatConversionSpecImpl conv,
-                     FormatSinkImpl *sink) {
+bool ConvertCharImpl(char v,
+                     const FormatConversionSpecImpl conv,
+                     FormatSinkImpl* sink) {
   size_t fill = 0;
-  if (conv.width() >= 0) fill = conv.width();
+  if (conv.width() >= 0)
+    fill = static_cast<size_t>(conv.width());
   ReducePadding(1, &fill);
   if (!conv.has_left_flag()) sink->Append(fill, ' ');
   sink->Append(1, v);
@@ -225,7 +228,8 @@ bool ConvertIntImplInnerSlow(const IntDigits &as_digits,
   // Print as a sequence of Substrings:
   //   [left_spaces][sign][base_indicator][zeroes][formatted][right_spaces]
   size_t fill = 0;
-  if (conv.width() >= 0) fill = conv.width();
+  if (conv.width() >= 0)
+    fill = static_cast<size_t>(conv.width());
 
   string_view formatted = as_digits.without_neg_or_zero();
   ReducePadding(formatted, &fill);
@@ -236,10 +240,9 @@ bool ConvertIntImplInnerSlow(const IntDigits &as_digits,
   string_view base_indicator = BaseIndicator(as_digits, conv);
   ReducePadding(base_indicator, &fill);
 
-  int precision = conv.precision();
-  bool precision_specified = precision >= 0;
-  if (!precision_specified)
-    precision = 1;
+  bool precision_specified = conv.precision() >= 0;
+  size_t precision =
+      precision_specified ? static_cast<size_t>(conv.precision()) : size_t{1};
 
   if (conv.has_alt_flag() &&
       conv.conversion_char() == FormatConversionCharInternal::o) {
@@ -247,7 +250,7 @@ bool ConvertIntImplInnerSlow(const IntDigits &as_digits,
     //   "For o conversion, it increases the precision (if necessary) to
     //   force the first digit of the result to be zero."
     if (formatted.empty() || *formatted.begin() != '0') {
-      int needed = static_cast<int>(formatted.size()) + 1;
+      size_t needed = formatted.size() + 1;
       precision = std::max(precision, needed);
     }
   }
@@ -287,7 +290,7 @@ bool ConvertIntArg(T v, const FormatConversionSpecImpl conv,
   // FormatConversionChar is declared, but not defined.
   switch (static_cast<uint8_t>(conv.conversion_char())) {
     case static_cast<uint8_t>(FormatConversionCharInternal::c):
-      return ConvertCharImpl(static_cast<unsigned char>(v), conv, sink);
+      return ConvertCharImpl(static_cast<char>(v), conv, sink);
 
     case static_cast<uint8_t>(FormatConversionCharInternal::o):
       as_digits.PrintAsOct(static_cast<U>(v));
@@ -375,7 +378,7 @@ FormatConvertImpl(const char *v, const FormatConversionSpecImpl conv,
     len = std::strlen(v);
   } else {
     // If precision is set, we look for the NUL-terminator on the valid range.
-    len = std::find(v, v + conv.precision(), '\0') - v;
+    len = static_cast<size_t>(std::find(v, v + conv.precision(), '\0') - v);
   }
   return {ConvertStringArg(string_view(v, len), conv, sink)};
 }
diff --git a/absl/strings/internal/str_format/bind.cc b/absl/strings/internal/str_format/bind.cc
index c988ba8f..77a42223 100644
--- a/absl/strings/internal/str_format/bind.cc
+++ b/absl/strings/internal/str_format/bind.cc
@@ -32,7 +32,8 @@ inline bool BindFromPosition(int position, int* value,
     return false;
   }
   // -1 because positions are 1-based
-  return FormatArgImplFriend::ToInt(pack[position - 1], value);
+  return FormatArgImplFriend::ToInt(pack[static_cast<size_t>(position) - 1],
+                                    value);
 }
 
 class ArgContext {
@@ -56,7 +57,7 @@ inline bool ArgContext::Bind(const UnboundConversion* unbound,
   const FormatArgImpl* arg = nullptr;
   int arg_position = unbound->arg_position;
   if (static_cast<size_t>(arg_position - 1) >= pack_.size()) return false;
-  arg = &pack_[arg_position - 1];  // 1-based
+  arg = &pack_[static_cast<size_t>(arg_position - 1)];  // 1-based
 
   if (unbound->flags != Flags::kBasic) {
     int width = unbound->width.value();
diff --git a/absl/strings/internal/str_format/extension.cc b/absl/strings/internal/str_format/extension.cc
index f93153d5..2a0ceb13 100644
--- a/absl/strings/internal/str_format/extension.cc
+++ b/absl/strings/internal/str_format/extension.cc
@@ -58,7 +58,8 @@ constexpr FormatConversionCharSet FormatConversionCharSetInternal::kPointer;
 bool FormatSinkImpl::PutPaddedString(string_view value, int width,
                                      int precision, bool left) {
   size_t space_remaining = 0;
-  if (width >= 0) space_remaining = width;
+  if (width >= 0)
+    space_remaining = static_cast<size_t>(width);
   size_t n = value.size();
   if (precision >= 0) n = std::min(n, static_cast<size_t>(precision));
   string_view shown(value.data(), n);
diff --git a/absl/strings/internal/str_format/float_conversion.cc b/absl/strings/internal/str_format/float_conversion.cc
index b1c40684..3895001a 100644
--- a/absl/strings/internal/str_format/float_conversion.cc
+++ b/absl/strings/internal/str_format/float_conversion.cc
@@ -92,27 +92,30 @@ class StackArray {
 
 // Calculates `10 * (*v) + carry` and stores the result in `*v` and returns
 // the carry.
+// Requires: `0 <= carry <= 9`
 template <typename Int>
-inline Int MultiplyBy10WithCarry(Int *v, Int carry) {
+inline char MultiplyBy10WithCarry(Int* v, char carry) {
   using BiggerInt = absl::conditional_t<sizeof(Int) == 4, uint64_t, uint128>;
-  BiggerInt tmp = 10 * static_cast<BiggerInt>(*v) + carry;
+  BiggerInt tmp =
+      10 * static_cast<BiggerInt>(*v) + static_cast<BiggerInt>(carry);
   *v = static_cast<Int>(tmp);
-  return static_cast<Int>(tmp >> (sizeof(Int) * 8));
+  return static_cast<char>(tmp >> (sizeof(Int) * 8));
 }
 
 // Calculates `(2^64 * carry + *v) / 10`.
 // Stores the quotient in `*v` and returns the remainder.
 // Requires: `0 <= carry <= 9`
-inline uint64_t DivideBy10WithCarry(uint64_t *v, uint64_t carry) {
+inline char DivideBy10WithCarry(uint64_t* v, char carry) {
   constexpr uint64_t divisor = 10;
   // 2^64 / divisor = chunk_quotient + chunk_remainder / divisor
   constexpr uint64_t chunk_quotient = (uint64_t{1} << 63) / (divisor / 2);
   constexpr uint64_t chunk_remainder = uint64_t{} - chunk_quotient * divisor;
 
+  const uint64_t carry_u64 = static_cast<uint64_t>(carry);
   const uint64_t mod = *v % divisor;
-  const uint64_t next_carry = chunk_remainder * carry + mod;
-  *v = *v / divisor + carry * chunk_quotient + next_carry / divisor;
-  return next_carry % divisor;
+  const uint64_t next_carry = chunk_remainder * carry_u64 + mod;
+  *v = *v / divisor + carry_u64 * chunk_quotient + next_carry / divisor;
+  return static_cast<char>(next_carry % divisor);
 }
 
 using MaxFloatType =
@@ -125,11 +128,11 @@ using MaxFloatType =
 //
 // Requires `0 <= exp` and `exp <= numeric_limits<MaxFloatType>::max_exponent`.
 class BinaryToDecimal {
-  static constexpr int ChunksNeeded(int exp) {
+  static constexpr size_t ChunksNeeded(int exp) {
     // We will left shift a uint128 by `exp` bits, so we need `128+exp` total
     // bits. Round up to 32.
     // See constructor for details about adding `10%` to the value.
-    return (128 + exp + 31) / 32 * 11 / 10;
+    return static_cast<size_t>((128 + exp + 31) / 32 * 11 / 10);
   }
 
  public:
@@ -140,7 +143,7 @@ class BinaryToDecimal {
     assert(exp > 0);
     assert(exp <= std::numeric_limits<MaxFloatType>::max_exponent);
     static_assert(
-        static_cast<int>(StackArray::kMaxCapacity) >=
+        StackArray::kMaxCapacity >=
             ChunksNeeded(std::numeric_limits<MaxFloatType>::max_exponent),
         "");
 
@@ -149,9 +152,9 @@ class BinaryToDecimal {
         [=](absl::Span<uint32_t> input) { f(BinaryToDecimal(input, v, exp)); });
   }
 
-  int TotalDigits() const {
-    return static_cast<int>((decimal_end_ - decimal_start_) * kDigitsPerChunk +
-                            CurrentDigits().size());
+  size_t TotalDigits() const {
+    return (decimal_end_ - decimal_start_) * kDigitsPerChunk +
+           CurrentDigits().size();
   }
 
   // See the current block of digits.
@@ -190,30 +193,31 @@ class BinaryToDecimal {
     // the decimal representation is around 7% less efficient in space than the
     // binary one. We allocate an extra 10% memory to account for this. See
     // ChunksNeeded for this calculation.
-    int chunk_index = exp / 32;
+    size_t after_chunk_index = static_cast<size_t>(exp / 32 + 1);
     decimal_start_ = decimal_end_ = ChunksNeeded(exp);
     const int offset = exp % 32;
     // Left shift v by exp bits.
-    data_[chunk_index] = static_cast<uint32_t>(v << offset);
+    data_[after_chunk_index - 1] = static_cast<uint32_t>(v << offset);
     for (v >>= (32 - offset); v; v >>= 32)
-      data_[++chunk_index] = static_cast<uint32_t>(v);
+      data_[++after_chunk_index - 1] = static_cast<uint32_t>(v);
 
-    while (chunk_index >= 0) {
+    while (after_chunk_index > 0) {
       // While we have more than one chunk available, go in steps of 1e9.
-      // `data_[chunk_index]` holds the highest non-zero binary chunk, so keep
-      // the variable updated.
+      // `data_[after_chunk_index - 1]` holds the highest non-zero binary chunk,
+      // so keep the variable updated.
       uint32_t carry = 0;
-      for (int i = chunk_index; i >= 0; --i) {
-        uint64_t tmp = uint64_t{data_[i]} + (uint64_t{carry} << 32);
-        data_[i] = static_cast<uint32_t>(tmp / uint64_t{1000000000});
+      for (size_t i = after_chunk_index; i > 0; --i) {
+        uint64_t tmp = uint64_t{data_[i - 1]} + (uint64_t{carry} << 32);
+        data_[i - 1] = static_cast<uint32_t>(tmp / uint64_t{1000000000});
         carry = static_cast<uint32_t>(tmp % uint64_t{1000000000});
       }
 
       // If the highest chunk is now empty, remove it from view.
-      if (data_[chunk_index] == 0) --chunk_index;
+      if (data_[after_chunk_index - 1] == 0)
+        --after_chunk_index;
 
       --decimal_start_;
-      assert(decimal_start_ != chunk_index);
+      assert(decimal_start_ != after_chunk_index - 1);
       data_[decimal_start_] = carry;
     }
 
@@ -225,13 +229,13 @@ class BinaryToDecimal {
   }
 
  private:
-  static constexpr int kDigitsPerChunk = 9;
+  static constexpr size_t kDigitsPerChunk = 9;
 
-  int decimal_start_;
-  int decimal_end_;
+  size_t decimal_start_;
+  size_t decimal_end_;
 
   char digits_[kDigitsPerChunk];
-  int size_ = 0;
+  size_t size_ = 0;
 
   absl::Span<uint32_t> data_;
 };
@@ -251,25 +255,26 @@ class FractionalDigitGenerator {
     static_assert(StackArray::kMaxCapacity >=
                       (Limits::digits + 128 - Limits::min_exponent + 31) / 32,
                   "");
-    StackArray::RunWithCapacity((Limits::digits + exp + 31) / 32,
-                                [=](absl::Span<uint32_t> input) {
-                                  f(FractionalDigitGenerator(input, v, exp));
-                                });
+    StackArray::RunWithCapacity(
+        static_cast<size_t>((Limits::digits + exp + 31) / 32),
+        [=](absl::Span<uint32_t> input) {
+          f(FractionalDigitGenerator(input, v, exp));
+        });
   }
 
   // Returns true if there are any more non-zero digits left.
-  bool HasMoreDigits() const { return next_digit_ != 0 || chunk_index_ >= 0; }
+  bool HasMoreDigits() const { return next_digit_ != 0 || after_chunk_index_; }
 
   // Returns true if the remainder digits are greater than 5000...
   bool IsGreaterThanHalf() const {
-    return next_digit_ > 5 || (next_digit_ == 5 && chunk_index_ >= 0);
+    return next_digit_ > 5 || (next_digit_ == 5 && after_chunk_index_);
   }
   // Returns true if the remainder digits are exactly 5000...
-  bool IsExactlyHalf() const { return next_digit_ == 5 && chunk_index_ < 0; }
+  bool IsExactlyHalf() const { return next_digit_ == 5 && !after_chunk_index_; }
 
   struct Digits {
-    int digit_before_nine;
-    int num_nines;
+    char digit_before_nine;
+    size_t num_nines;
   };
 
   // Get the next set of digits.
@@ -288,35 +293,37 @@ class FractionalDigitGenerator {
 
  private:
   // Return the next digit.
-  int GetOneDigit() {
-    if (chunk_index_ < 0) return 0;
+  char GetOneDigit() {
+    if (!after_chunk_index_)
+      return 0;
 
-    uint32_t carry = 0;
-    for (int i = chunk_index_; i >= 0; --i) {
-      carry = MultiplyBy10WithCarry(&data_[i], carry);
+    char carry = 0;
+    for (size_t i = after_chunk_index_; i > 0; --i) {
+      carry = MultiplyBy10WithCarry(&data_[i - 1], carry);
     }
     // If the lowest chunk is now empty, remove it from view.
-    if (data_[chunk_index_] == 0) --chunk_index_;
+    if (data_[after_chunk_index_ - 1] == 0)
+      --after_chunk_index_;
     return carry;
   }
 
   FractionalDigitGenerator(absl::Span<uint32_t> data, uint128 v, int exp)
-      : chunk_index_(exp / 32), data_(data) {
+      : after_chunk_index_(static_cast<size_t>(exp / 32 + 1)), data_(data) {
     const int offset = exp % 32;
     // Right shift `v` by `exp` bits.
-    data_[chunk_index_] = static_cast<uint32_t>(v << (32 - offset));
+    data_[after_chunk_index_ - 1] = static_cast<uint32_t>(v << (32 - offset));
     v >>= offset;
     // Make sure we don't overflow the data. We already calculated that
     // non-zero bits fit, so we might not have space for leading zero bits.
-    for (int pos = chunk_index_; v; v >>= 32)
+    for (size_t pos = after_chunk_index_ - 1; v; v >>= 32)
       data_[--pos] = static_cast<uint32_t>(v);
 
     // Fill next_digit_, as GetDigits expects it to be populated always.
     next_digit_ = GetOneDigit();
   }
 
-  int next_digit_;
-  int chunk_index_;
+  char next_digit_;
+  size_t after_chunk_index_;
   absl::Span<uint32_t> data_;
 };
 
@@ -362,7 +369,7 @@ char *PrintIntegralDigitsFromRightFast(uint128 v, char *p) {
   auto low = static_cast<uint64_t>(v);
 
   while (high != 0) {
-    uint64_t carry = DivideBy10WithCarry(&high, 0);
+    char carry = DivideBy10WithCarry(&high, 0);
     carry = DivideBy10WithCarry(&low, carry);
     *--p = carry + '0';
   }
@@ -373,13 +380,15 @@ char *PrintIntegralDigitsFromRightFast(uint128 v, char *p) {
 // shifting.
 // Performs rounding if necessary to fit within `precision`.
 // Returns the pointer to one after the last character written.
-char *PrintFractionalDigitsFast(uint64_t v, char *start, int exp,
-                                int precision) {
+char* PrintFractionalDigitsFast(uint64_t v,
+                                char* start,
+                                int exp,
+                                size_t precision) {
   char *p = start;
   v <<= (64 - exp);
   while (precision > 0) {
     if (!v) return p;
-    *p++ = MultiplyBy10WithCarry(&v, uint64_t{0}) + '0';
+    *p++ = MultiplyBy10WithCarry(&v, 0) + '0';
     --precision;
   }
 
@@ -393,8 +402,6 @@ char *PrintFractionalDigitsFast(uint64_t v, char *start, int exp,
     RoundToEven(p - 1);
   }
 
-  assert(precision == 0);
-  // Precision can only be zero here.
   return p;
 }
 
@@ -402,8 +409,10 @@ char *PrintFractionalDigitsFast(uint64_t v, char *start, int exp,
 // after shifting.
 // Performs rounding if necessary to fit within `precision`.
 // Returns the pointer to one after the last character written.
-char *PrintFractionalDigitsFast(uint128 v, char *start, int exp,
-                                int precision) {
+char* PrintFractionalDigitsFast(uint128 v,
+                                char* start,
+                                int exp,
+                                size_t precision) {
   char *p = start;
   v <<= (128 - exp);
   auto high = static_cast<uint64_t>(v >> 64);
@@ -412,7 +421,7 @@ char *PrintFractionalDigitsFast(uint128 v, char *start, int exp,
   // While we have digits to print and `low` is not empty, do the long
   // multiplication.
   while (precision > 0 && low != 0) {
-    uint64_t carry = MultiplyBy10WithCarry(&low, uint64_t{0});
+    char carry = MultiplyBy10WithCarry(&low, 0);
     carry = MultiplyBy10WithCarry(&high, carry);
 
     *p++ = carry + '0';
@@ -424,7 +433,7 @@ char *PrintFractionalDigitsFast(uint128 v, char *start, int exp,
   // above.
   while (precision > 0) {
     if (!high) return p;
-    *p++ = MultiplyBy10WithCarry(&high, uint64_t{0}) + '0';
+    *p++ = MultiplyBy10WithCarry(&high, 0) + '0';
     --precision;
   }
 
@@ -438,14 +447,12 @@ char *PrintFractionalDigitsFast(uint128 v, char *start, int exp,
     RoundToEven(p - 1);
   }
 
-  assert(precision == 0);
-  // Precision can only be zero here.
   return p;
 }
 
 struct FormatState {
   char sign_char;
-  int precision;
+  size_t precision;
   const FormatConversionSpecImpl &conv;
   FormatSinkImpl *sink;
 
@@ -455,9 +462,9 @@ struct FormatState {
 };
 
 struct Padding {
-  int left_spaces;
-  int zeros;
-  int right_spaces;
+  size_t left_spaces;
+  size_t zeros;
+  size_t right_spaces;
 };
 
 Padding ExtraWidthToPadding(size_t total_size, const FormatState &state) {
@@ -465,7 +472,7 @@ Padding ExtraWidthToPadding(size_t total_size, const FormatState &state) {
       static_cast<size_t>(state.conv.width()) <= total_size) {
     return {0, 0, 0};
   }
-  int missing_chars = state.conv.width() - total_size;
+  size_t missing_chars = static_cast<size_t>(state.conv.width()) - total_size;
   if (state.conv.has_left_flag()) {
     return {0, 0, missing_chars};
   } else if (state.conv.has_zero_flag()) {
@@ -475,8 +482,10 @@ Padding ExtraWidthToPadding(size_t total_size, const FormatState &state) {
   }
 }
 
-void FinalPrint(const FormatState &state, absl::string_view data,
-                int padding_offset, int trailing_zeros,
+void FinalPrint(const FormatState& state,
+                absl::string_view data,
+                size_t padding_offset,
+                size_t trailing_zeros,
                 absl::string_view data_postfix) {
   if (state.conv.width() < 0) {
     // No width specified. Fast-path.
@@ -487,10 +496,10 @@ void FinalPrint(const FormatState &state, absl::string_view data,
     return;
   }
 
-  auto padding = ExtraWidthToPadding((state.sign_char != '\0' ? 1 : 0) +
-                                         data.size() + data_postfix.size() +
-                                         static_cast<size_t>(trailing_zeros),
-                                     state);
+  auto padding =
+      ExtraWidthToPadding((state.sign_char != '\0' ? 1 : 0) + data.size() +
+                              data_postfix.size() + trailing_zeros,
+                          state);
 
   state.sink->Append(padding.left_spaces, ' ');
   if (state.sign_char != '\0') state.sink->Append(1, state.sign_char);
@@ -547,15 +556,16 @@ void FormatFFast(Int v, int exp, const FormatState &state) {
     if (integral_digits_start[-1] != '0') --integral_digits_start;
   }
 
-  size_t size = fractional_digits_end - integral_digits_start;
+  size_t size =
+      static_cast<size_t>(fractional_digits_end - integral_digits_start);
 
   // In `alt` mode (flag #) we keep the `.` even if there are no fractional
   // digits. In non-alt mode, we strip it.
   if (!state.ShouldPrintDot()) --size;
   FinalPrint(state, absl::string_view(integral_digits_start, size),
              /*padding_offset=*/0,
-             static_cast<int>(state.precision - (fractional_digits_end -
-                                                 fractional_digits_start)),
+             state.precision - static_cast<size_t>(fractional_digits_end -
+                                                   fractional_digits_start),
              /*data_postfix=*/"");
 }
 
@@ -567,21 +577,22 @@ void FormatFFast(Int v, int exp, const FormatState &state) {
 void FormatFPositiveExpSlow(uint128 v, int exp, const FormatState &state) {
   BinaryToDecimal::RunConversion(v, exp, [&](BinaryToDecimal btd) {
     const size_t total_digits =
-        btd.TotalDigits() +
-        (state.ShouldPrintDot() ? static_cast<size_t>(state.precision) + 1 : 0);
+        btd.TotalDigits() + (state.ShouldPrintDot() ? state.precision + 1 : 0);
 
     const auto padding = ExtraWidthToPadding(
         total_digits + (state.sign_char != '\0' ? 1 : 0), state);
 
     state.sink->Append(padding.left_spaces, ' ');
-    if (state.sign_char != '\0') state.sink->Append(1, state.sign_char);
+    if (state.sign_char != '\0')
+      state.sink->Append(1, state.sign_char);
     state.sink->Append(padding.zeros, '0');
 
     do {
       state.sink->Append(btd.CurrentDigits());
     } while (btd.AdvanceDigits());
 
-    if (state.ShouldPrintDot()) state.sink->Append(1, '.');
+    if (state.ShouldPrintDot())
+      state.sink->Append(1, '.');
     state.sink->Append(state.precision, '0');
     state.sink->Append(padding.right_spaces, ' ');
   });
@@ -594,8 +605,7 @@ void FormatFPositiveExpSlow(uint128 v, int exp, const FormatState &state) {
 // digits.
 void FormatFNegativeExpSlow(uint128 v, int exp, const FormatState &state) {
   const size_t total_digits =
-      /* 0 */ 1 +
-      (state.ShouldPrintDot() ? static_cast<size_t>(state.precision) + 1 : 0);
+      /* 0 */ 1 + (state.ShouldPrintDot() ? state.precision + 1 : 0);
   auto padding =
       ExtraWidthToPadding(total_digits + (state.sign_char ? 1 : 0), state);
   padding.zeros += 1;
@@ -606,7 +616,7 @@ void FormatFNegativeExpSlow(uint128 v, int exp, const FormatState &state) {
   if (state.ShouldPrintDot()) state.sink->Append(1, '.');
 
   // Print digits
-  int digits_to_go = state.precision;
+  size_t digits_to_go = state.precision;
 
   FractionalDigitGenerator::RunConversion(
       v, exp, [&](FractionalDigitGenerator digit_gen) {
@@ -666,7 +676,8 @@ void FormatFNegativeExpSlow(uint128 v, int exp, const FormatState &state) {
 template <typename Int>
 void FormatF(Int mantissa, int exp, const FormatState &state) {
   if (exp >= 0) {
-    const int total_bits = sizeof(Int) * 8 - LeadingZeros(mantissa) + exp;
+    const int total_bits =
+        static_cast<int>(sizeof(Int) * 8) - LeadingZeros(mantissa) + exp;
 
     // Fallback to the slow stack-based approach if we can't do it in a 64 or
     // 128 bit state.
@@ -686,9 +697,9 @@ void FormatF(Int mantissa, int exp, const FormatState &state) {
 // Grab the group of four bits (nibble) from `n`. E.g., nibble 1 corresponds to
 // bits 4-7.
 template <typename Int>
-uint8_t GetNibble(Int n, int nibble_index) {
+uint8_t GetNibble(Int n, size_t nibble_index) {
   constexpr Int mask_low_nibble = Int{0xf};
-  int shift = nibble_index * 4;
+  int shift = static_cast<int>(nibble_index * 4);
   n &= mask_low_nibble << shift;
   return static_cast<uint8_t>((n >> shift) & 0xf);
 }
@@ -696,9 +707,9 @@ uint8_t GetNibble(Int n, int nibble_index) {
 // Add one to the given nibble, applying carry to higher nibbles. Returns true
 // if overflow, false otherwise.
 template <typename Int>
-bool IncrementNibble(int nibble_index, Int *n) {
-  constexpr int kShift = sizeof(Int) * 8 - 1;
-  constexpr int kNumNibbles = sizeof(Int) * 8 / 4;
+bool IncrementNibble(size_t nibble_index, Int* n) {
+  constexpr size_t kShift = sizeof(Int) * 8 - 1;
+  constexpr size_t kNumNibbles = sizeof(Int) * 8 / 4;
   Int before = *n >> kShift;
   // Here we essentially want to take the number 1 and move it into the requsted
   // nibble, then add it to *n to effectively increment the nibble. However,
@@ -706,28 +717,32 @@ bool IncrementNibble(int nibble_index, Int *n) {
   // i.e., if the nibble_index is out of range. So therefore we check for this
   // and if we are out of range we just add 0 which leaves *n unchanged, which
   // seems like the reasonable thing to do in that case.
-  *n += ((nibble_index >= kNumNibbles) ? 0 : (Int{1} << (nibble_index * 4)));
+  *n += ((nibble_index >= kNumNibbles)
+             ? 0
+             : (Int{1} << static_cast<int>(nibble_index * 4)));
   Int after = *n >> kShift;
   return (before && !after) || (nibble_index >= kNumNibbles);
 }
 
 // Return a mask with 1's in the given nibble and all lower nibbles.
 template <typename Int>
-Int MaskUpToNibbleInclusive(int nibble_index) {
-  constexpr int kNumNibbles = sizeof(Int) * 8 / 4;
+Int MaskUpToNibbleInclusive(size_t nibble_index) {
+  constexpr size_t kNumNibbles = sizeof(Int) * 8 / 4;
   static const Int ones = ~Int{0};
-  return ones >> std::max(0, 4 * (kNumNibbles - nibble_index - 1));
+  ++nibble_index;
+  return ones >> static_cast<int>(
+                     4 * (std::max(kNumNibbles, nibble_index) - nibble_index));
 }
 
 // Return a mask with 1's below the given nibble.
 template <typename Int>
-Int MaskUpToNibbleExclusive(int nibble_index) {
-  return nibble_index <= 0 ? 0 : MaskUpToNibbleInclusive<Int>(nibble_index - 1);
+Int MaskUpToNibbleExclusive(size_t nibble_index) {
+  return nibble_index == 0 ? 0 : MaskUpToNibbleInclusive<Int>(nibble_index - 1);
 }
 
 template <typename Int>
-Int MoveToNibble(uint8_t nibble, int nibble_index) {
-  return Int{nibble} << (4 * nibble_index);
+Int MoveToNibble(uint8_t nibble, size_t nibble_index) {
+  return Int{nibble} << static_cast<int>(4 * nibble_index);
 }
 
 // Given mantissa size, find optimal # of mantissa bits to put in initial digit.
@@ -744,10 +759,10 @@ Int MoveToNibble(uint8_t nibble, int nibble_index) {
 // a multiple of four. Once again, the goal is to have all fractional digits
 // represent real precision.
 template <typename Float>
-constexpr int HexFloatLeadingDigitSizeInBits() {
+constexpr size_t HexFloatLeadingDigitSizeInBits() {
   return std::numeric_limits<Float>::digits % 4 > 0
-             ? std::numeric_limits<Float>::digits % 4
-             : 4;
+             ? static_cast<size_t>(std::numeric_limits<Float>::digits % 4)
+             : size_t{4};
 }
 
 // This function captures the rounding behavior of glibc for hex float
@@ -757,16 +772,17 @@ constexpr int HexFloatLeadingDigitSizeInBits() {
 // point that is not followed by 800000..., it disregards the parity and rounds
 // up if > 8 and rounds down if < 8.
 template <typename Int>
-bool HexFloatNeedsRoundUp(Int mantissa, int final_nibble_displayed,
+bool HexFloatNeedsRoundUp(Int mantissa,
+                          size_t final_nibble_displayed,
                           uint8_t leading) {
   // If the last nibble (hex digit) to be displayed is the lowest on in the
   // mantissa then that means that we don't have any further nibbles to inform
   // rounding, so don't round.
-  if (final_nibble_displayed <= 0) {
+  if (final_nibble_displayed == 0) {
     return false;
   }
-  int rounding_nibble_idx = final_nibble_displayed - 1;
-  constexpr int kTotalNibbles = sizeof(Int) * 8 / 4;
+  size_t rounding_nibble_idx = final_nibble_displayed - 1;
+  constexpr size_t kTotalNibbles = sizeof(Int) * 8 / 4;
   assert(final_nibble_displayed <= kTotalNibbles);
   Int mantissa_up_to_rounding_nibble_inclusive =
       mantissa & MaskUpToNibbleInclusive<Int>(rounding_nibble_idx);
@@ -793,7 +809,7 @@ struct HexFloatTypeParams {
   }
 
   int min_exponent;
-  int leading_digit_size_bits;
+  size_t leading_digit_size_bits;
 };
 
 // Hex Float Rounding. First check if we need to round; if so, then we do that
@@ -803,10 +819,12 @@ struct HexFloatTypeParams {
 template <typename Int>
 void FormatARound(bool precision_specified, const FormatState &state,
                   uint8_t *leading, Int *mantissa, int *exp) {
-  constexpr int kTotalNibbles = sizeof(Int) * 8 / 4;
+  constexpr size_t kTotalNibbles = sizeof(Int) * 8 / 4;
   // Index of the last nibble that we could display given precision.
-  int final_nibble_displayed =
-      precision_specified ? std::max(0, (kTotalNibbles - state.precision)) : 0;
+  size_t final_nibble_displayed =
+      precision_specified
+          ? (std::max(kTotalNibbles, state.precision) - state.precision)
+          : 0;
   if (HexFloatNeedsRoundUp(*mantissa, final_nibble_displayed, *leading)) {
     // Need to round up.
     bool overflow = IncrementNibble(final_nibble_displayed, mantissa);
@@ -830,9 +848,9 @@ void FormatARound(bool precision_specified, const FormatState &state,
 template <typename Int>
 void FormatANormalize(const HexFloatTypeParams float_traits, uint8_t *leading,
                       Int *mantissa, int *exp) {
-  constexpr int kIntBits = sizeof(Int) * 8;
+  constexpr size_t kIntBits = sizeof(Int) * 8;
   static const Int kHighIntBit = Int{1} << (kIntBits - 1);
-  const int kLeadDigitBitsCount = float_traits.leading_digit_size_bits;
+  const size_t kLeadDigitBitsCount = float_traits.leading_digit_size_bits;
   // Normalize mantissa so that highest bit set is in MSB position, unless we
   // get interrupted by the exponent threshold.
   while (*mantissa && !(*mantissa & kHighIntBit)) {
@@ -846,18 +864,18 @@ void FormatANormalize(const HexFloatTypeParams float_traits, uint8_t *leading,
   }
   // Extract bits for leading digit then shift them away leaving the
   // fractional part.
-  *leading =
-      static_cast<uint8_t>(*mantissa >> (kIntBits - kLeadDigitBitsCount));
-  *exp -= (*mantissa != 0) ? kLeadDigitBitsCount : *exp;
-  *mantissa <<= kLeadDigitBitsCount;
+  *leading = static_cast<uint8_t>(
+      *mantissa >> static_cast<int>(kIntBits - kLeadDigitBitsCount));
+  *exp -= (*mantissa != 0) ? static_cast<int>(kLeadDigitBitsCount) : *exp;
+  *mantissa <<= static_cast<int>(kLeadDigitBitsCount);
 }
 
 template <typename Int>
 void FormatA(const HexFloatTypeParams float_traits, Int mantissa, int exp,
              bool uppercase, const FormatState &state) {
   // Int properties.
-  constexpr int kIntBits = sizeof(Int) * 8;
-  constexpr int kTotalNibbles = sizeof(Int) * 8 / 4;
+  constexpr size_t kIntBits = sizeof(Int) * 8;
+  constexpr size_t kTotalNibbles = sizeof(Int) * 8 / 4;
   // Did the user specify a precision explicitly?
   const bool precision_specified = state.conv.precision() >= 0;
 
@@ -903,16 +921,19 @@ void FormatA(const HexFloatTypeParams float_traits, Int mantissa, int exp,
   }
 
   // ============ Fractional Digits ============
-  int digits_emitted = 0;
+  size_t digits_emitted = 0;
   while (mantissa > 0) {
     *digits_iter++ = digits[GetNibble(mantissa, kTotalNibbles - 1)];
     mantissa <<= 4;
     ++digits_emitted;
   }
-  int trailing_zeros =
-      precision_specified ? state.precision - digits_emitted : 0;
-  assert(trailing_zeros >= 0);
-  auto digits_result = string_view(digits_buffer, digits_iter - digits_buffer);
+  size_t trailing_zeros = 0;
+  if (precision_specified) {
+    assert(state.precision >= digits_emitted);
+    trailing_zeros = state.precision - digits_emitted;
+  }
+  auto digits_result = string_view(
+      digits_buffer, static_cast<size_t>(digits_iter - digits_buffer));
 
   // =============== Exponent ==================
   constexpr size_t kBufSizeForExpDecRepr =
@@ -925,11 +946,11 @@ void FormatA(const HexFloatTypeParams float_traits, Int mantissa, int exp,
   numbers_internal::FastIntToBuffer(exp < 0 ? -exp : exp, exp_buffer + 2);
 
   // ============ Assemble Result ==============
-  FinalPrint(state,           //
-             digits_result,   // 0xN.NNN...
-             2,               // offset in `data` to start padding if needed.
-             trailing_zeros,  // num remaining mantissa padding zeros
-             exp_buffer);     // exponent
+  FinalPrint(state,
+             digits_result,                        // 0xN.NNN...
+             2,                                    // offset of any padding
+             static_cast<size_t>(trailing_zeros),  // remaining mantissa padding
+             exp_buffer);                          // exponent
 }
 
 char *CopyStringTo(absl::string_view v, char *out) {
@@ -961,10 +982,10 @@ bool FallbackToSnprintf(const Float v, const FormatConversionSpecImpl &conv,
     int n = snprintf(&space[0], space.size(), fmt, w, p, v);
     if (n < 0) return false;
     if (static_cast<size_t>(n) < space.size()) {
-      result = absl::string_view(space.data(), n);
+      result = absl::string_view(space.data(), static_cast<size_t>(n));
       break;
     }
-    space.resize(n + 1);
+    space.resize(static_cast<size_t>(n) + 1);
   }
   sink->Append(result);
   return true;
@@ -972,13 +993,13 @@ bool FallbackToSnprintf(const Float v, const FormatConversionSpecImpl &conv,
 
 // 128-bits in decimal: ceil(128*log(2)/log(10))
 //   or std::numeric_limits<__uint128_t>::digits10
-constexpr int kMaxFixedPrecision = 39;
+constexpr size_t kMaxFixedPrecision = 39;
 
-constexpr int kBufferLength = /*sign*/ 1 +
-                              /*integer*/ kMaxFixedPrecision +
-                              /*point*/ 1 +
-                              /*fraction*/ kMaxFixedPrecision +
-                              /*exponent e+123*/ 5;
+constexpr size_t kBufferLength = /*sign*/ 1 +
+                                 /*integer*/ kMaxFixedPrecision +
+                                 /*point*/ 1 +
+                                 /*fraction*/ kMaxFixedPrecision +
+                                 /*exponent e+123*/ 5;
 
 struct Buffer {
   void push_front(char c) {
@@ -1001,7 +1022,7 @@ struct Buffer {
 
   char last_digit() const { return end[-1] == '.' ? end[-2] : end[-1]; }
 
-  int size() const { return static_cast<int>(end - begin); }
+  size_t size() const { return static_cast<size_t>(end - begin); }
 
   char data[kBufferLength];
   char *begin;
@@ -1030,8 +1051,9 @@ bool ConvertNonNumericFloats(char sign_char, Float v,
     return false;
   }
 
-  return sink->PutPaddedString(string_view(text, ptr - text), conv.width(), -1,
-                               conv.has_left_flag());
+  return sink->PutPaddedString(
+      string_view(text, static_cast<size_t>(ptr - text)), conv.width(), -1,
+      conv.has_left_flag());
 }
 
 // Round up the last digit of the value.
@@ -1068,11 +1090,11 @@ void PrintExponent(int exp, char e, Buffer *out) {
   }
   // Exponent digits.
   if (exp > 99) {
-    out->push_back(exp / 100 + '0');
+    out->push_back(static_cast<char>(exp / 100) + '0');
     out->push_back(exp / 10 % 10 + '0');
     out->push_back(exp % 10 + '0');
   } else {
-    out->push_back(exp / 10 + '0');
+    out->push_back(static_cast<char>(exp / 10) + '0');
     out->push_back(exp % 10 + '0');
   }
 }
@@ -1115,8 +1137,8 @@ Decomposed<Float> Decompose(Float v) {
 // In Fixed mode, we add a '.' at the end.
 // In Precision mode, we add a '.' after the first digit.
 template <FormatStyle mode, typename Int>
-int PrintIntegralDigits(Int digits, Buffer *out) {
-  int printed = 0;
+size_t PrintIntegralDigits(Int digits, Buffer* out) {
+  size_t printed = 0;
   if (digits) {
     for (; digits; digits /= 10) out->push_front(digits % 10 + '0');
     printed = out->size();
@@ -1135,10 +1157,10 @@ int PrintIntegralDigits(Int digits, Buffer *out) {
 }
 
 // Back out 'extra_digits' digits and round up if necessary.
-bool RemoveExtraPrecision(int extra_digits, bool has_leftover_value,
-                          Buffer *out, int *exp_out) {
-  if (extra_digits <= 0) return false;
-
+void RemoveExtraPrecision(size_t extra_digits,
+                          bool has_leftover_value,
+                          Buffer* out,
+                          int* exp_out) {
   // Back out the extra digits
   out->end -= extra_digits;
 
@@ -1158,15 +1180,17 @@ bool RemoveExtraPrecision(int extra_digits, bool has_leftover_value,
   if (needs_to_round_up) {
     RoundUp<FormatStyle::Precision>(out, exp_out);
   }
-  return true;
 }
 
 // Print the value into the buffer.
 // This will not include the exponent, which will be returned in 'exp_out' for
 // Precision mode.
 template <typename Int, typename Float, FormatStyle mode>
-bool FloatToBufferImpl(Int int_mantissa, int exp, int precision, Buffer *out,
-                       int *exp_out) {
+bool FloatToBufferImpl(Int int_mantissa,
+                       int exp,
+                       size_t precision,
+                       Buffer* out,
+                       int* exp_out) {
   assert((CanFitMantissa<Float, Int>()));
 
   const int int_bits = std::numeric_limits<Int>::digits;
@@ -1182,14 +1206,16 @@ bool FloatToBufferImpl(Int int_mantissa, int exp, int precision, Buffer *out,
       // The value will overflow the Int
       return false;
     }
-    int digits_printed = PrintIntegralDigits<mode>(int_mantissa << exp, out);
-    int digits_to_zero_pad = precision;
+    size_t digits_printed = PrintIntegralDigits<mode>(int_mantissa << exp, out);
+    size_t digits_to_zero_pad = precision;
     if (mode == FormatStyle::Precision) {
-      *exp_out = digits_printed - 1;
-      digits_to_zero_pad -= digits_printed - 1;
-      if (RemoveExtraPrecision(-digits_to_zero_pad, false, out, exp_out)) {
+      *exp_out = static_cast<int>(digits_printed - 1);
+      if (digits_to_zero_pad < digits_printed - 1) {
+        RemoveExtraPrecision(digits_printed - 1 - digits_to_zero_pad, false,
+                             out, exp_out);
         return true;
       }
+      digits_to_zero_pad -= digits_printed - 1;
     }
     for (; digits_to_zero_pad-- > 0;) out->push_back('0');
     return true;
@@ -1203,10 +1229,10 @@ bool FloatToBufferImpl(Int int_mantissa, int exp, int precision, Buffer *out,
   const Int mask = (Int{1} << exp) - 1;
 
   // Print the integral part first.
-  int digits_printed = PrintIntegralDigits<mode>(int_mantissa >> exp, out);
+  size_t digits_printed = PrintIntegralDigits<mode>(int_mantissa >> exp, out);
   int_mantissa &= mask;
 
-  int fractional_count = precision;
+  size_t fractional_count = precision;
   if (mode == FormatStyle::Precision) {
     if (digits_printed == 0) {
       // Find the first non-zero digit, when in Precision mode.
@@ -1222,20 +1248,21 @@ bool FloatToBufferImpl(Int int_mantissa, int exp, int precision, Buffer *out,
       int_mantissa &= mask;
     } else {
       // We already have a digit, and a '.'
-      *exp_out = digits_printed - 1;
-      fractional_count -= *exp_out;
-      if (RemoveExtraPrecision(-fractional_count, int_mantissa != 0, out,
-                               exp_out)) {
+      *exp_out = static_cast<int>(digits_printed - 1);
+      if (fractional_count < digits_printed - 1) {
         // If we had enough digits, return right away.
         // The code below will try to round again otherwise.
+        RemoveExtraPrecision(digits_printed - 1 - fractional_count,
+                             int_mantissa != 0, out, exp_out);
         return true;
       }
+      fractional_count -= digits_printed - 1;
     }
   }
 
   auto get_next_digit = [&] {
     int_mantissa *= 10;
-    int digit = static_cast<int>(int_mantissa >> exp);
+    char digit = static_cast<char>(int_mantissa >> exp);
     int_mantissa &= mask;
     return digit;
   };
@@ -1245,7 +1272,7 @@ bool FloatToBufferImpl(Int int_mantissa, int exp, int precision, Buffer *out,
     out->push_back(get_next_digit() + '0');
   }
 
-  int next_digit = get_next_digit();
+  char next_digit = get_next_digit();
   if (next_digit > 5 ||
       (next_digit == 5 && (int_mantissa || out->last_digit() % 2 == 1))) {
     RoundUp<mode>(out, exp_out);
@@ -1255,24 +1282,25 @@ bool FloatToBufferImpl(Int int_mantissa, int exp, int precision, Buffer *out,
 }
 
 template <FormatStyle mode, typename Float>
-bool FloatToBuffer(Decomposed<Float> decomposed, int precision, Buffer *out,
-                   int *exp) {
+bool FloatToBuffer(Decomposed<Float> decomposed,
+                   size_t precision,
+                   Buffer* out,
+                   int* exp) {
   if (precision > kMaxFixedPrecision) return false;
 
   // Try with uint64_t.
   if (CanFitMantissa<Float, std::uint64_t>() &&
       FloatToBufferImpl<std::uint64_t, Float, mode>(
-          static_cast<std::uint64_t>(decomposed.mantissa),
-          static_cast<std::uint64_t>(decomposed.exponent), precision, out, exp))
+          static_cast<std::uint64_t>(decomposed.mantissa), decomposed.exponent,
+          precision, out, exp))
     return true;
 
 #if defined(ABSL_HAVE_INTRINSIC_INT128)
   // If that is not enough, try with __uint128_t.
   return CanFitMantissa<Float, __uint128_t>() &&
          FloatToBufferImpl<__uint128_t, Float, mode>(
-             static_cast<__uint128_t>(decomposed.mantissa),
-             static_cast<__uint128_t>(decomposed.exponent), precision, out,
-             exp);
+             static_cast<__uint128_t>(decomposed.mantissa), decomposed.exponent,
+             precision, out, exp);
 #endif
   return false;
 }
@@ -1280,12 +1308,15 @@ bool FloatToBuffer(Decomposed<Float> decomposed, int precision, Buffer *out,
 void WriteBufferToSink(char sign_char, absl::string_view str,
                        const FormatConversionSpecImpl &conv,
                        FormatSinkImpl *sink) {
-  int left_spaces = 0, zeros = 0, right_spaces = 0;
-  int missing_chars =
-      conv.width() >= 0 ? std::max(conv.width() - static_cast<int>(str.size()) -
-                                       static_cast<int>(sign_char != 0),
-                                   0)
-                        : 0;
+  size_t left_spaces = 0, zeros = 0, right_spaces = 0;
+  size_t missing_chars = 0;
+  if (conv.width() >= 0) {
+    const size_t conv_width_size_t = static_cast<size_t>(conv.width());
+    const size_t existing_chars =
+        str.size() + static_cast<size_t>(sign_char != 0);
+    if (conv_width_size_t > existing_chars)
+      missing_chars = conv_width_size_t - existing_chars;
+  }
   if (conv.has_left_flag()) {
     right_spaces = missing_chars;
   } else if (conv.has_zero_flag()) {
@@ -1321,7 +1352,8 @@ bool FloatToSink(const Float v, const FormatConversionSpecImpl &conv,
     return true;
   }
 
-  int precision = conv.precision() < 0 ? 6 : conv.precision();
+  size_t precision =
+      conv.precision() < 0 ? 6 : static_cast<size_t>(conv.precision());
 
   int exp = 0;
 
@@ -1348,12 +1380,12 @@ bool FloatToSink(const Float v, const FormatConversionSpecImpl &conv,
         &buffer);
   } else if (c == FormatConversionCharInternal::g ||
              c == FormatConversionCharInternal::G) {
-    precision = std::max(0, precision - 1);
+    precision = std::max(precision, size_t{1}) - 1;
     if (!FloatToBuffer<FormatStyle::Precision>(decomposed, precision, &buffer,
                                                &exp)) {
       return FallbackToSnprintf(v, conv, sink);
     }
-    if (precision + 1 > exp && exp >= -4) {
+    if ((exp < 0 || precision + 1 > static_cast<size_t>(exp)) && exp >= -4) {
       if (exp < 0) {
         // Have 1.23456, needs 0.00123456
         // Move the first digit
@@ -1388,9 +1420,11 @@ bool FloatToSink(const Float v, const FormatConversionSpecImpl &conv,
     return false;
   }
 
-  WriteBufferToSink(sign_char,
-                    absl::string_view(buffer.begin, buffer.end - buffer.begin),
-                    conv, sink);
+  WriteBufferToSink(
+      sign_char,
+      absl::string_view(buffer.begin,
+                        static_cast<size_t>(buffer.end - buffer.begin)),
+      conv, sink);
 
   return true;
 }