Rollback of fix "unsafe narrowing" warnings in absl, 8/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 */internal/.)

Bug: chromium:1292951
PiperOrigin-RevId: 471561809
Change-Id: I7abd6d83706f5ca135f1ce3458192a498a6280b9

3 files changed, 9 insertions, 11 deletions

diff --git a/absl/base/internal/direct_mmap.h b/absl/base/internal/direct_mmap.h
index 815b8d23..e492bb00 100644
--- a/absl/base/internal/direct_mmap.h
+++ b/absl/base/internal/direct_mmap.h
@@ -97,8 +97,7 @@ inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
 #ifdef __BIONIC__
   // SYS_mmap2 has problems on Android API level <= 16.
   // Workaround by invoking __mmap2() instead.
-  return __mmap2(start, length, prot, flags, fd,
-                 static_cast<size_t>(offset / pagesize));
+  return __mmap2(start, length, prot, flags, fd, offset / pagesize);
 #else
   return reinterpret_cast<void*>(
       syscall(SYS_mmap2, start, length, prot, flags, fd,
diff --git a/absl/base/internal/low_level_alloc.cc b/absl/base/internal/low_level_alloc.cc
index 662167b0..aa6c3c3c 100644
--- a/absl/base/internal/low_level_alloc.cc
+++ b/absl/base/internal/low_level_alloc.cc
@@ -332,7 +332,7 @@ size_t GetPageSize() {
 #elif defined(__wasm__) || defined(__asmjs__)
   return getpagesize();
 #else
-  return static_cast<size_t>(sysconf(_SC_PAGESIZE));
+  return sysconf(_SC_PAGESIZE);
 #endif
 }
 
diff --git a/absl/base/internal/sysinfo.cc b/absl/base/internal/sysinfo.cc
index d820ce38..a3e08b93 100644
--- a/absl/base/internal/sysinfo.cc
+++ b/absl/base/internal/sysinfo.cc
@@ -136,7 +136,7 @@ static int GetNumCPUs() {
   // Other possibilities:
   //  - Read /sys/devices/system/cpu/online and use cpumask_parse()
   //  - sysconf(_SC_NPROCESSORS_ONLN)
-  return static_cast<int>(std::thread::hardware_concurrency());
+  return std::thread::hardware_concurrency();
 #endif
 }
 
@@ -194,7 +194,7 @@ static bool ReadLongFromFile(const char *file, long *value) {
     char line[1024];
     char *err;
     memset(line, '\0', sizeof(line));
-    ssize_t len = read(fd, line, sizeof(line) - 1);
+    int len = read(fd, line, sizeof(line) - 1);
     if (len <= 0) {
       ret = false;
     } else {
@@ -376,7 +376,7 @@ pid_t GetTID() {
 #endif
 
 pid_t GetTID() {
-  return static_cast<pid_t>(syscall(SYS_gettid));
+  return syscall(SYS_gettid);
 }
 
 #elif defined(__akaros__)
@@ -429,11 +429,11 @@ static constexpr int kBitsPerWord = 32;  // tid_array is uint32_t.
 // Returns the TID to tid_array.
 static void FreeTID(void *v) {
   intptr_t tid = reinterpret_cast<intptr_t>(v);
-  intptr_t word = tid / kBitsPerWord;
+  int word = tid / kBitsPerWord;
   uint32_t mask = ~(1u << (tid % kBitsPerWord));
   absl::base_internal::SpinLockHolder lock(&tid_lock);
   assert(0 <= word && static_cast<size_t>(word) < tid_array->size());
-  (*tid_array)[static_cast<size_t>(word)] &= mask;
+  (*tid_array)[word] &= mask;
 }
 
 static void InitGetTID() {
@@ -455,7 +455,7 @@ pid_t GetTID() {
 
   intptr_t tid = reinterpret_cast<intptr_t>(pthread_getspecific(tid_key));
   if (tid != 0) {
-    return static_cast<pid_t>(tid);
+    return tid;
   }
 
   int bit;  // tid_array[word] = 1u << bit;
@@ -476,8 +476,7 @@ pid_t GetTID() {
     while (bit < kBitsPerWord && (((*tid_array)[word] >> bit) & 1) != 0) {
       ++bit;
     }
-    tid =
-        static_cast<intptr_t>((word * kBitsPerWord) + static_cast<size_t>(bit));
+    tid = (word * kBitsPerWord) + bit;
     (*tid_array)[word] |= 1u << bit;  // Mark the TID as allocated.
   }