Fix "unsafe narrowing" warnings in absl, 3/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 dirs n-t, except string.)

Bug: chromium:1292951
PiperOrigin-RevId: 465287204
Change-Id: I0fe98ff78bf3c08d86992019eb626755f8b6803e

4 files changed, 24 insertions, 17 deletions

diff --git a/absl/time/clock.cc b/absl/time/clock.cc
index 7b204c4e..dba31611 100644
--- a/absl/time/clock.cc
+++ b/absl/time/clock.cc
@@ -217,9 +217,11 @@ static int64_t GetCurrentTimeNanosFromKernel(uint64_t last_cycleclock,
   uint64_t elapsed_cycles;
   int loops = 0;
   do {
-    before_cycles = GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW();
+    before_cycles =
+        static_cast<uint64_t>(GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW());
     current_time_nanos_from_system = GET_CURRENT_TIME_NANOS_FROM_SYSTEM();
-    after_cycles = GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW();
+    after_cycles =
+        static_cast<uint64_t>(GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW());
     // elapsed_cycles is unsigned, so is large on overflow
     elapsed_cycles = after_cycles - before_cycles;
     if (elapsed_cycles >= local_approx_syscall_time_in_cycles &&
@@ -316,7 +318,8 @@ int64_t GetCurrentTimeNanos() {
   // contribute to register pressure - reading it early before initializing
   // the other pieces of the calculation minimizes spill/restore instructions,
   // minimizing icache cost.
-  uint64_t now_cycles = GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW();
+  uint64_t now_cycles =
+      static_cast<uint64_t>(GET_CURRENT_TIME_NANOS_CYCLECLOCK_NOW());
 
   // Acquire pairs with the barrier in SeqRelease - if this load sees that
   // store, the shared-data reads necessarily see that SeqRelease's updates
@@ -356,7 +359,8 @@ int64_t GetCurrentTimeNanos() {
   uint64_t delta_cycles;
   if (seq_read0 == seq_read1 && (seq_read0 & 1) == 0 &&
       (delta_cycles = now_cycles - base_cycles) < min_cycles_per_sample) {
-    return base_ns + ((delta_cycles * nsscaled_per_cycle) >> kScale);
+    return static_cast<int64_t>(
+        base_ns + ((delta_cycles * nsscaled_per_cycle) >> kScale));
   }
   return GetCurrentTimeNanosSlowPath();
 }
@@ -404,8 +408,8 @@ static int64_t GetCurrentTimeNanosSlowPath()
   // Sample the kernel time base.  This is the definition of
   // "now" if we take the slow path.
   uint64_t now_cycles;
-  uint64_t now_ns =
-      GetCurrentTimeNanosFromKernel(time_state.last_now_cycles, &now_cycles);
+  uint64_t now_ns = static_cast<uint64_t>(
+      GetCurrentTimeNanosFromKernel(time_state.last_now_cycles, &now_cycles));
   time_state.last_now_cycles = now_cycles;
 
   uint64_t estimated_base_ns;
@@ -432,7 +436,7 @@ static int64_t GetCurrentTimeNanosSlowPath()
 
   time_state.lock.Unlock();
 
-  return estimated_base_ns;
+  return static_cast<int64_t>(estimated_base_ns);
 }
 
 // Main part of the algorithm.  Locks out readers, updates the approximation
@@ -489,7 +493,8 @@ static uint64_t UpdateLastSample(uint64_t now_cycles, uint64_t now_ns,
     uint64_t assumed_next_sample_delta_cycles =
         SafeDivideAndScale(kMinNSBetweenSamples, measured_nsscaled_per_cycle);
 
-    int64_t diff_ns = now_ns - estimated_base_ns;  // estimate low by this much
+    // Estimate low by this much.
+    int64_t diff_ns = static_cast<int64_t>(now_ns - estimated_base_ns);
 
     // We want to set nsscaled_per_cycle so that our estimate of the ns time
     // at the assumed cycle time is the assumed ns time.
@@ -500,7 +505,8 @@ static uint64_t UpdateLastSample(uint64_t now_cycles, uint64_t now_ns,
     // of our current error, by solving:
     //  kMinNSBetweenSamples + diff_ns - (diff_ns / 16) ==
     //  (assumed_next_sample_delta_cycles * nsscaled_per_cycle) >> kScale
-    ns = kMinNSBetweenSamples + diff_ns - (diff_ns / 16);
+    ns = static_cast<uint64_t>(static_cast<int64_t>(kMinNSBetweenSamples) +
+                               diff_ns - (diff_ns / 16));
     uint64_t new_nsscaled_per_cycle =
         SafeDivideAndScale(ns, assumed_next_sample_delta_cycles);
     if (new_nsscaled_per_cycle != 0 &&
@@ -558,7 +564,7 @@ constexpr absl::Duration MaxSleep() {
 // REQUIRES: to_sleep <= MaxSleep().
 void SleepOnce(absl::Duration to_sleep) {
 #ifdef _WIN32
-  Sleep(to_sleep / absl::Milliseconds(1));
+  Sleep(static_cast<DWORD>(to_sleep / absl::Milliseconds(1)));
 #else
   struct timespec sleep_time = absl::ToTimespec(to_sleep);
   while (nanosleep(&sleep_time, &sleep_time) != 0 && errno == EINTR) {
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index 2bba62da..1f4cf382 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -645,7 +645,7 @@ timeval ToTimeval(Duration d) {
       ts.tv_nsec -= 1000 * 1000 * 1000;
     }
   }
-  tv.tv_sec = ts.tv_sec;
+  tv.tv_sec = static_cast<decltype(tv.tv_sec)>(ts.tv_sec);
   if (tv.tv_sec != ts.tv_sec) {  // narrowing
     if (ts.tv_sec < 0) {
       tv.tv_sec = std::numeric_limits<decltype(tv.tv_sec)>::min();
@@ -728,7 +728,7 @@ void AppendNumberUnit(std::string* out, int64_t n, DisplayUnit unit) {
   char* const ep = buf + sizeof(buf);
   char* bp = Format64(ep, 0, n);
   if (*bp != '0' || bp + 1 != ep) {
-    out->append(bp, ep - bp);
+    out->append(bp, static_cast<size_t>(ep - bp));
     out->append(unit.abbr.data(), unit.abbr.size());
   }
 }
@@ -745,12 +745,12 @@ void AppendNumberUnit(std::string* out, double n, DisplayUnit unit) {
   int64_t int_part = d;
   if (int_part != 0 || frac_part != 0) {
     char* bp = Format64(ep, 0, int_part);  // always < 1000
-    out->append(bp, ep - bp);
+    out->append(bp, static_cast<size_t>(ep - bp));
     if (frac_part != 0) {
       out->push_back('.');
       bp = Format64(ep, prec, frac_part);
       while (ep[-1] == '0') --ep;
-      out->append(bp, ep - bp);
+      out->append(bp, static_cast<size_t>(ep - bp));
     }
     out->append(unit.abbr.data(), unit.abbr.size());
   }
@@ -841,7 +841,7 @@ bool ConsumeDurationNumber(const char** dpp, const char* ep, int64_t* int_part,
 // in "*unit".  The given string pointer is modified to point to the first
 // unconsumed char.
 bool ConsumeDurationUnit(const char** start, const char* end, Duration* unit) {
-  size_t size = end - *start;
+  size_t size = static_cast<size_t>(end - *start);
   switch (size) {
     case 0:
       return false;
diff --git a/absl/time/format.cc b/absl/time/format.cc
index 4005fb70..15a26b14 100644
--- a/absl/time/format.cc
+++ b/absl/time/format.cc
@@ -64,7 +64,8 @@ cctz_parts Split(absl::Time t) {
 // details about rep_hi and rep_lo.
 absl::Time Join(const cctz_parts& parts) {
   const int64_t rep_hi = (parts.sec - unix_epoch()).count();
-  const uint32_t rep_lo = parts.fem.count() / (1000 * 1000 / 4);
+  const uint32_t rep_lo =
+      static_cast<uint32_t>(parts.fem.count() / (1000 * 1000 / 4));
   const auto d = time_internal::MakeDuration(rep_hi, rep_lo);
   return time_internal::FromUnixDuration(d);
 }
diff --git a/absl/time/time.cc b/absl/time/time.cc
index 1ec2026e..718b88c8 100644
--- a/absl/time/time.cc
+++ b/absl/time/time.cc
@@ -316,7 +316,7 @@ timespec ToTimespec(Time t) {
 timeval ToTimeval(Time t) {
   timeval tv;
   timespec ts = absl::ToTimespec(t);
-  tv.tv_sec = ts.tv_sec;
+  tv.tv_sec = static_cast<decltype(tv.tv_sec)>(ts.tv_sec);
   if (tv.tv_sec != ts.tv_sec) {  // narrowing
     if (ts.tv_sec < 0) {
       tv.tv_sec = std::numeric_limits<decltype(tv.tv_sec)>::min();