Fix "unsafe narrowing" warnings in absl, 1/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 .h and win32 .inc files.)

Bug: chromium:1292951
PiperOrigin-RevId: 463835431
Change-Id: If8e5f7f651d5cd96035e23e4623bdb08a7fedabe

5 files changed, 43 insertions, 24 deletions

diff --git a/absl/strings/cord_buffer.h b/absl/strings/cord_buffer.h
index 56a6ce6f..09a74ad5 100644
--- a/absl/strings/cord_buffer.h
+++ b/absl/strings/cord_buffer.h
@@ -330,8 +330,7 @@ class CordBuffer {
 
     // Returns the available area of the internal SSO data
     absl::Span<char> short_available() {
-      assert(is_short());
-      const size_t length = (short_rep.raw_size >> 1);
+      const size_t length = short_length();
       return absl::Span<char>(short_rep.data + length,
                               kInlineCapacity - length);
     }
@@ -347,7 +346,7 @@ class CordBuffer {
     // Returns the length of the internal SSO data.
     size_t short_length() const {
       assert(is_short());
-      return short_rep.raw_size >> 1;
+      return static_cast<size_t>(short_rep.raw_size >> 1);
     }
 
     // Sets the length of the internal SSO data.
diff --git a/absl/strings/internal/char_map.h b/absl/strings/internal/char_map.h
index 61484de0..5aabc1fc 100644
--- a/absl/strings/internal/char_map.h
+++ b/absl/strings/internal/char_map.h
@@ -103,10 +103,9 @@ class Charmap {
   constexpr Charmap(uint64_t b0, uint64_t b1, uint64_t b2, uint64_t b3)
       : m_{b0, b1, b2, b3} {}
 
-  static constexpr uint64_t RangeForWord(unsigned char lo, unsigned char hi,
-                                         uint64_t word) {
-    return OpenRangeFromZeroForWord(hi + 1, word) &
-           ~OpenRangeFromZeroForWord(lo, word);
+  static constexpr uint64_t RangeForWord(char lo, char hi, uint64_t word) {
+    return OpenRangeFromZeroForWord(static_cast<unsigned char>(hi) + 1, word) &
+           ~OpenRangeFromZeroForWord(static_cast<unsigned char>(lo), word);
   }
 
   // All the chars in the specified word of the range [0, upper).
@@ -119,13 +118,16 @@ class Charmap {
                      : (~static_cast<uint64_t>(0) >> (64 - upper % 64));
   }
 
-  static constexpr uint64_t CharMaskForWord(unsigned char x, uint64_t word) {
-    return (x / 64 == word) ? (static_cast<uint64_t>(1) << (x % 64)) : 0;
+  static constexpr uint64_t CharMaskForWord(char x, uint64_t word) {
+    const auto unsigned_x = static_cast<unsigned char>(x);
+    return (unsigned_x / 64 == word)
+               ? (static_cast<uint64_t>(1) << (unsigned_x % 64))
+               : 0;
   }
 
- private:
-  void SetChar(unsigned char c) {
-    m_[c / 64] |= static_cast<uint64_t>(1) << (c % 64);
+  void SetChar(char c) {
+    const auto unsigned_c = static_cast<unsigned char>(c);
+    m_[unsigned_c / 64] |= static_cast<uint64_t>(1) << (unsigned_c % 64);
   }
 
   uint64_t m_[4];
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h
index b50fb79a..29954112 100644
--- a/absl/strings/internal/cord_internal.h
+++ b/absl/strings/internal/cord_internal.h
@@ -570,7 +570,7 @@ class InlineData {
   // Requires the current instance to hold inline data.
   size_t inline_size() const {
     assert(!is_tree());
-    return tag() >> 1;
+    return static_cast<size_t>(tag()) >> 1;
   }
 
   // Sets the size of the inlined character data inside this instance.
diff --git a/absl/strings/internal/str_format/parser.h b/absl/strings/internal/str_format/parser.h
index 32b91d03..a81bac83 100644
--- a/absl/strings/internal/str_format/parser.h
+++ b/absl/strings/internal/str_format/parser.h
@@ -155,10 +155,11 @@ bool ParseFormatString(string_view src, Consumer consumer) {
         static_cast<const char*>(memchr(p, '%', static_cast<size_t>(end - p)));
     if (!percent) {
       // We found the last substring.
-      return consumer.Append(string_view(p, end - p));
+      return consumer.Append(string_view(p, static_cast<size_t>(end - p)));
     }
     // We found a percent, so push the text run then process the percent.
-    if (ABSL_PREDICT_FALSE(!consumer.Append(string_view(p, percent - p)))) {
+    if (ABSL_PREDICT_FALSE(!consumer.Append(
+            string_view(p, static_cast<size_t>(percent - p))))) {
       return false;
     }
     if (ABSL_PREDICT_FALSE(percent + 1 >= end)) return false;
@@ -189,7 +190,8 @@ bool ParseFormatString(string_view src, Consumer consumer) {
       p = ConsumeUnboundConversion(percent + 1, end, &conv, &next_arg);
       if (ABSL_PREDICT_FALSE(p == nullptr)) return false;
       if (ABSL_PREDICT_FALSE(!consumer.ConvertOne(
-          conv, string_view(percent + 1, p - (percent + 1))))) {
+              conv, string_view(percent + 1,
+                                static_cast<size_t>(p - (percent + 1)))))) {
         return false;
       }
     } else {
diff --git a/absl/strings/substitute.h b/absl/strings/substitute.h
index 6d2b08ab..692fd03c 100644
--- a/absl/strings/substitute.h
+++ b/absl/strings/substitute.h
@@ -125,28 +125,44 @@ class Arg {
   }
   Arg(short value)  // NOLINT(*)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(unsigned short value)  // NOLINT(*)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(int value)  // NOLINT(runtime/explicit)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(unsigned int value)  // NOLINT(runtime/explicit)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(long value)  // NOLINT(*)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(unsigned long value)  // NOLINT(*)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(long long value)  // NOLINT(*)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(unsigned long long value)  // NOLINT(*)
       : piece_(scratch_,
-               numbers_internal::FastIntToBuffer(value, scratch_) - scratch_) {}
+               static_cast<size_t>(
+                   numbers_internal::FastIntToBuffer(value, scratch_) -
+                   scratch_)) {}
   Arg(float value)  // NOLINT(runtime/explicit)
       : piece_(scratch_, numbers_internal::SixDigitsToBuffer(value, scratch_)) {
   }