Revert "[libc] Enable -Wconversion for tests. (#127523)"

This reverts commit 1e6e845d49a336e9da7ca6c576ec45c0b419b5f6 because it
changed the 1st parameter of adjust() to be unsigned, but libc itself
calls adjust() with a negative argument in align_backward() in
op_generic.h.

23 files changed, 100 insertions, 128 deletions

diff --git a/libc/src/__support/CPP/bit.h b/libc/src/__support/CPP/bit.h
index 7d138201783b..82b9eb512826 100644
--- a/libc/src/__support/CPP/bit.h
+++ b/libc/src/__support/CPP/bit.h
@@ -101,7 +101,7 @@ countr_zero(T value) {
     shift >>= 1;
     mask >>= shift;
   }
-  return static_cast<int>(zero_bits);
+  return zero_bits;
 }
 #if __has_builtin(__builtin_ctzs)
 ADD_SPECIALIZATION(countr_zero, unsigned short, __builtin_ctzs)
@@ -140,7 +140,7 @@ countl_zero(T value) {
     else
       zero_bits |= shift;
   }
-  return static_cast<int>(zero_bits);
+  return zero_bits;
 }
 #if __has_builtin(__builtin_clzs)
 ADD_SPECIALIZATION(countl_zero, unsigned short, __builtin_clzs)
@@ -226,7 +226,7 @@ rotr(T value, int rotate);
 template <typename T>
 [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
 rotl(T value, int rotate) {
-  constexpr int N = cpp::numeric_limits<T>::digits;
+  constexpr unsigned N = cpp::numeric_limits<T>::digits;
   rotate = rotate % N;
   if (!rotate)
     return value;
@@ -238,7 +238,7 @@ rotl(T value, int rotate) {
 template <typename T>
 [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, T>
 rotr(T value, int rotate) {
-  constexpr int N = cpp::numeric_limits<T>::digits;
+  constexpr unsigned N = cpp::numeric_limits<T>::digits;
   rotate = rotate % N;
   if (!rotate)
     return value;
diff --git a/libc/src/__support/CPP/span.h b/libc/src/__support/CPP/span.h
index 9234a26d201c..a41c9b744e37 100644
--- a/libc/src/__support/CPP/span.h
+++ b/libc/src/__support/CPP/span.h
@@ -11,7 +11,6 @@
 #include <stddef.h> // For size_t
 
 #include "array.h" // For array
-#include "limits.h"
 #include "src/__support/macros/config.h"
 #include "type_traits.h" // For remove_cv_t, enable_if_t, is_same_v, is_const_v
 
@@ -49,8 +48,7 @@ public:
   using const_reference = const T &;
   using iterator = T *;
 
-  LIBC_INLINE_VAR static constexpr size_type dynamic_extent =
-      cpp::numeric_limits<size_type>::max();
+  LIBC_INLINE_VAR static constexpr size_type dynamic_extent = -1;
 
   LIBC_INLINE constexpr span() : span_data(nullptr), span_size(0) {}
 
@@ -60,7 +58,7 @@ public:
       : span_data(first), span_size(count) {}
 
   LIBC_INLINE constexpr span(pointer first, pointer end)
-      : span_data(first), span_size(static_cast<size_t>(end - first)) {}
+      : span_data(first), span_size(end - first) {}
 
   template <typename U, size_t N,
             cpp::enable_if_t<is_compatible_v<U>, bool> = true>
diff --git a/libc/src/__support/CPP/string.h b/libc/src/__support/CPP/string.h
index 1ac04c7f1f9d..dbc0ae04e5e6 100644
--- a/libc/src/__support/CPP/string.h
+++ b/libc/src/__support/CPP/string.h
@@ -67,8 +67,7 @@ public:
       : string(cstr, ::LIBC_NAMESPACE::internal::string_length(cstr)) {}
   LIBC_INLINE string(size_t size_, char value) {
     resize(size_);
-    static_assert(sizeof(char) == sizeof(uint8_t));
-    inline_memset((void *)buffer_, static_cast<uint8_t>(value), size_);
+    inline_memset((void *)buffer_, value, size_);
   }
 
   LIBC_INLINE string &operator=(const string &other) {
diff --git a/libc/src/__support/CPP/string_view.h b/libc/src/__support/CPP/string_view.h
index aa15814b2e14..745c62c35f0a 100644
--- a/libc/src/__support/CPP/string_view.h
+++ b/libc/src/__support/CPP/string_view.h
@@ -9,7 +9,6 @@
 #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_STRING_VIEW_H
 #define LLVM_LIBC_SRC___SUPPORT_CPP_STRING_VIEW_H
 
-#include "limits.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 
@@ -41,7 +40,7 @@ private:
   LIBC_INLINE static constexpr size_t length(const char *Str) {
     for (const char *End = Str;; ++End)
       if (*End == '\0')
-        return static_cast<size_t>(End - Str);
+        return End - Str;
   }
 
   LIBC_INLINE bool equals(string_view Other) const {
@@ -62,8 +61,7 @@ public:
 
   // special value equal to the maximum value representable by the type
   // size_type.
-  LIBC_INLINE_VAR static constexpr size_t npos =
-      cpp::numeric_limits<size_t>::max();
+  LIBC_INLINE_VAR static constexpr size_t npos = -1;
 
   LIBC_INLINE constexpr string_view() : Data(nullptr), Len(0) {}
 
diff --git a/libc/src/__support/FPUtil/FPBits.h b/libc/src/__support/FPUtil/FPBits.h
index bee8d0a8dc47..90b6e406e0f3 100644
--- a/libc/src/__support/FPUtil/FPBits.h
+++ b/libc/src/__support/FPUtil/FPBits.h
@@ -247,11 +247,11 @@ protected:
     using UP::UP;
 
     LIBC_INLINE constexpr BiasedExponent(Exponent exp)
-        : UP(static_cast<uint32_t>(static_cast<int32_t>(exp) + EXP_BIAS)) {}
+        : UP(static_cast<int32_t>(exp) + EXP_BIAS) {}
 
     // Cast operator to get convert from BiasedExponent to Exponent.
     LIBC_INLINE constexpr operator Exponent() const {
-      return Exponent(static_cast<int32_t>(UP::value - EXP_BIAS));
+      return Exponent(UP::value - EXP_BIAS);
     }
 
     LIBC_INLINE constexpr BiasedExponent &operator++() {
@@ -686,7 +686,7 @@ public:
   }
 
   LIBC_INLINE constexpr void set_biased_exponent(StorageType biased) {
-    UP::set_biased_exponent(BiasedExponent(static_cast<uint32_t>(biased)));
+    UP::set_biased_exponent(BiasedExponent((int32_t)biased));
   }
 
   LIBC_INLINE constexpr int get_exponent() const {
diff --git a/libc/src/__support/FPUtil/NormalFloat.h b/libc/src/__support/FPUtil/NormalFloat.h
index a2f285fc6fb9..b4cbb5042a68 100644
--- a/libc/src/__support/FPUtil/NormalFloat.h
+++ b/libc/src/__support/FPUtil/NormalFloat.h
@@ -105,7 +105,7 @@ template <typename T> struct NormalFloat {
 
     constexpr int SUBNORMAL_EXPONENT = -FPBits<T>::EXP_BIAS + 1;
     if (exponent < SUBNORMAL_EXPONENT) {
-      unsigned shift = static_cast<unsigned>(SUBNORMAL_EXPONENT - exponent);
+      unsigned shift = SUBNORMAL_EXPONENT - exponent;
       // Since exponent > subnormalExponent, shift is strictly greater than
       // zero.
       if (shift <= FPBits<T>::FRACTION_LEN + 1) {
@@ -160,7 +160,7 @@ private:
     if (bits.is_subnormal()) {
       unsigned shift = evaluate_normalization_shift(bits.get_mantissa());
       mantissa = static_cast<StorageType>(bits.get_mantissa() << shift);
-      exponent = 1 - FPBits<T>::EXP_BIAS - static_cast<int32_t>(shift);
+      exponent = 1 - FPBits<T>::EXP_BIAS - shift;
     } else {
       exponent = bits.get_biased_exponent() - FPBits<T>::EXP_BIAS;
       mantissa = ONE | bits.get_mantissa();
diff --git a/libc/src/__support/FPUtil/aarch64/FEnvImpl.h b/libc/src/__support/FPUtil/aarch64/FEnvImpl.h
index 914155a01631..18b0631324f8 100644
--- a/libc/src/__support/FPUtil/aarch64/FEnvImpl.h
+++ b/libc/src/__support/FPUtil/aarch64/FEnvImpl.h
@@ -110,7 +110,7 @@ LIBC_INLINE int enable_except(int excepts) {
       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
   controlWord |= (newExcepts << FEnv::ExceptionControlFlagsBitPosition);
   FEnv::writeControlWord(controlWord);
-  return FEnv::exceptionStatusToMacro(static_cast<uint32_t>(oldExcepts));
+  return FEnv::exceptionStatusToMacro(oldExcepts);
 }
 
 LIBC_INLINE int disable_except(int excepts) {
@@ -120,12 +120,12 @@ LIBC_INLINE int disable_except(int excepts) {
       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
   controlWord &= ~(disabledExcepts << FEnv::ExceptionControlFlagsBitPosition);
   FEnv::writeControlWord(controlWord);
-  return FEnv::exceptionStatusToMacro(static_cast<uint32_t>(oldExcepts));
+  return FEnv::exceptionStatusToMacro(oldExcepts);
 }
 
 LIBC_INLINE int get_except() {
   uint32_t controlWord = FEnv::getControlWord();
-  uint32_t enabledExcepts =
+  int enabledExcepts =
       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
   return FEnv::exceptionStatusToMacro(enabledExcepts);
 }
@@ -250,10 +250,8 @@ LIBC_INLINE int set_round(int mode) {
   }
 
   uint32_t controlWord = FEnv::getControlWord();
-  controlWord &=
-      static_cast<uint32_t>(~(0x3 << FEnv::RoundingControlBitPosition));
-  controlWord |=
-      static_cast<uint32_t>(bitValue << FEnv::RoundingControlBitPosition);
+  controlWord &= ~(0x3 << FEnv::RoundingControlBitPosition);
+  controlWord |= (bitValue << FEnv::RoundingControlBitPosition);
   FEnv::writeControlWord(controlWord);
 
   return 0;
diff --git a/libc/src/__support/FPUtil/aarch64/fenv_darwin_impl.h b/libc/src/__support/FPUtil/aarch64/fenv_darwin_impl.h
index dcce76b6116b..969e70796d1f 100644
--- a/libc/src/__support/FPUtil/aarch64/fenv_darwin_impl.h
+++ b/libc/src/__support/FPUtil/aarch64/fenv_darwin_impl.h
@@ -63,7 +63,7 @@ struct FEnv {
   // __fpcr_flush_to_zero bit in the FPCR register.  This control bit is
   // located in a different place from FE_FLUSHTOZERO status bit relative to
   // the other exceptions.
-  LIBC_INLINE static uint32_t exception_value_from_status(uint32_t status) {
+  LIBC_INLINE static uint32_t exception_value_from_status(int status) {
     return ((status & FE_INVALID) ? EX_INVALID : 0) |
            ((status & FE_DIVBYZERO) ? EX_DIVBYZERO : 0) |
            ((status & FE_OVERFLOW) ? EX_OVERFLOW : 0) |
@@ -72,7 +72,7 @@ struct FEnv {
            ((status & FE_FLUSHTOZERO) ? EX_FLUSHTOZERO : 0);
   }
 
-  LIBC_INLINE static uint32_t exception_value_from_control(uint32_t control) {
+  LIBC_INLINE static uint32_t exception_value_from_control(int control) {
     return ((control & __fpcr_trap_invalid) ? EX_INVALID : 0) |
            ((control & __fpcr_trap_divbyzero) ? EX_DIVBYZERO : 0) |
            ((control & __fpcr_trap_overflow) ? EX_OVERFLOW : 0) |
@@ -81,7 +81,7 @@ struct FEnv {
            ((control & __fpcr_flush_to_zero) ? EX_FLUSHTOZERO : 0);
   }
 
-  LIBC_INLINE static uint32_t exception_value_to_status(uint32_t excepts) {
+  LIBC_INLINE static int exception_value_to_status(uint32_t excepts) {
     return ((excepts & EX_INVALID) ? FE_INVALID : 0) |
            ((excepts & EX_DIVBYZERO) ? FE_DIVBYZERO : 0) |
            ((excepts & EX_OVERFLOW) ? FE_OVERFLOW : 0) |
@@ -90,7 +90,7 @@ struct FEnv {
            ((excepts & EX_FLUSHTOZERO) ? FE_FLUSHTOZERO : 0);
   }
 
-  LIBC_INLINE static uint32_t exception_value_to_control(uint32_t excepts) {
+  LIBC_INLINE static int exception_value_to_control(uint32_t excepts) {
     return ((excepts & EX_INVALID) ? __fpcr_trap_invalid : 0) |
            ((excepts & EX_DIVBYZERO) ? __fpcr_trap_divbyzero : 0) |
            ((excepts & EX_OVERFLOW) ? __fpcr_trap_overflow : 0) |
@@ -113,37 +113,34 @@ struct FEnv {
 };
 
 LIBC_INLINE int enable_except(int excepts) {
-  uint32_t new_excepts =
-      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
+  uint32_t new_excepts = FEnv::exception_value_from_status(excepts);
   uint32_t control_word = FEnv::get_control_word();
   uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
   if (new_excepts != old_excepts) {
     control_word |= FEnv::exception_value_to_control(new_excepts);
     FEnv::set_control_word(control_word);
   }
-  return static_cast<int>(FEnv::exception_value_to_status(old_excepts));
+  return FEnv::exception_value_to_status(old_excepts);
 }
 
 LIBC_INLINE int disable_except(int excepts) {
-  uint32_t disabled_excepts =
-      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
+  uint32_t disabled_excepts = FEnv::exception_value_from_status(excepts);
   uint32_t control_word = FEnv::get_control_word();
   uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
   control_word &= ~FEnv::exception_value_to_control(disabled_excepts);
   FEnv::set_control_word(control_word);
-  return static_cast<int>(FEnv::exception_value_to_status(old_excepts));
+  return FEnv::exception_value_to_status(old_excepts);
 }
 
 LIBC_INLINE int get_except() {
   uint32_t control_word = FEnv::get_control_word();
   uint32_t enabled_excepts = FEnv::exception_value_from_control(control_word);
-  return static_cast<int>(FEnv::exception_value_to_status(enabled_excepts));
+  return FEnv::exception_value_to_status(enabled_excepts);
 }
 
 LIBC_INLINE int clear_except(int excepts) {
   uint32_t status_word = FEnv::get_status_word();
-  uint32_t except_value =
-      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
+  uint32_t except_value = FEnv::exception_value_from_status(excepts);
   status_word &= ~FEnv::exception_value_to_status(except_value);
   FEnv::set_status_word(status_word);
   return 0;
@@ -151,16 +148,13 @@ LIBC_INLINE int clear_except(int excepts) {
 
 LIBC_INLINE int test_except(int excepts) {
   uint32_t statusWord = FEnv::get_status_word();
-  uint32_t ex_value =
-      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
-  return static_cast<int>(statusWord &
-                          FEnv::exception_value_to_status(ex_value));
+  uint32_t ex_value = FEnv::exception_value_from_status(excepts);
+  return statusWord & FEnv::exception_value_to_status(ex_value);
 }
 
 LIBC_INLINE int set_except(int excepts) {
   uint32_t status_word = FEnv::get_status_word();
-  uint32_t new_exceptions =
-      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
+  uint32_t new_exceptions = FEnv::exception_value_from_status(excepts);
   status_word |= FEnv::exception_value_to_status(new_exceptions);
   FEnv::set_status_word(status_word);
   return 0;
@@ -180,8 +174,7 @@ LIBC_INLINE int raise_except(int excepts) {
                          : "s0", "s1" /* s0 and s1 are clobbered */);
   };
 
-  uint32_t to_raise =
-      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
+  uint32_t to_raise = FEnv::exception_value_from_status(excepts);
   int result = 0;
 
   if (to_raise & FEnv::EX_INVALID) {
@@ -244,7 +237,7 @@ LIBC_INLINE int get_round() {
 }
 
 LIBC_INLINE int set_round(int mode) {
-  uint32_t bit_value;
+  uint16_t bit_value;
   switch (mode) {
   case FE_TONEAREST:
     bit_value = FEnv::TONEAREST;
@@ -263,7 +256,7 @@ LIBC_INLINE int set_round(int mode) {
   }
 
   uint32_t control_word = FEnv::get_control_word();
-  control_word &= ~(0x3u << FEnv::ROUNDING_CONTROL_BIT_POSITION);
+  control_word &= ~(0x3 << FEnv::ROUNDING_CONTROL_BIT_POSITION);
   control_word |= (bit_value << FEnv::ROUNDING_CONTROL_BIT_POSITION);
   FEnv::set_control_word(control_word);
 
diff --git a/libc/src/__support/FPUtil/generic/sqrt_80_bit_long_double.h b/libc/src/__support/FPUtil/generic/sqrt_80_bit_long_double.h
index 0ba836d17a08..9492d52da045 100644
--- a/libc/src/__support/FPUtil/generic/sqrt_80_bit_long_double.h
+++ b/libc/src/__support/FPUtil/generic/sqrt_80_bit_long_double.h
@@ -24,7 +24,7 @@ namespace x86 {
 LIBC_INLINE void normalize(int &exponent,
                            FPBits<long double>::StorageType &mantissa) {
   const unsigned int shift = static_cast<unsigned int>(
-      static_cast<size_t>(cpp::countl_zero(static_cast<uint64_t>(mantissa))) -
+      cpp::countl_zero(static_cast<uint64_t>(mantissa)) -
       (8 * sizeof(uint64_t) - 1 - FPBits<long double>::FRACTION_LEN));
   exponent -= shift;
   mantissa <<= shift;
diff --git a/libc/src/__support/OSUtil/darwin/io.h b/libc/src/__support/OSUtil/darwin/io.h
index 69df99da522f..a5f7ecbd7036 100644
--- a/libc/src/__support/OSUtil/darwin/io.h
+++ b/libc/src/__support/OSUtil/darwin/io.h
@@ -17,8 +17,7 @@ namespace LIBC_NAMESPACE_DECL {
 
 LIBC_INLINE void write_to_stderr(cpp::string_view msg) {
   LIBC_NAMESPACE::syscall_impl(4 /*SYS_write*/, 2 /* stderr */,
-                               reinterpret_cast<long>(msg.data()),
-                               static_cast<long>(msg.size()));
+                               reinterpret_cast<long>(msg.data()), msg.size());
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/__support/big_int.h b/libc/src/__support/big_int.h
index f44624a7eafc..e726a094b5da 100644
--- a/libc/src/__support/big_int.h
+++ b/libc/src/__support/big_int.h
@@ -284,7 +284,7 @@ LIBC_INLINE constexpr cpp::array<word, N> shift(cpp::array<word, N> array,
     if (i < 0)
       return 0;
     if (i >= int(N))
-      return is_neg ? cpp::numeric_limits<word>::max() : 0;
+      return is_neg ? -1 : 0;
     return array[i];
   };
   const size_t index_offset = offset / WORD_BITS;
@@ -696,8 +696,7 @@ public:
     }
     BigInt quotient;
     WordType x_word = static_cast<WordType>(x);
-    constexpr size_t LOG2_WORD_SIZE =
-        static_cast<size_t>(cpp::bit_width(WORD_SIZE) - 1);
+    constexpr size_t LOG2_WORD_SIZE = cpp::bit_width(WORD_SIZE) - 1;
     constexpr size_t HALF_WORD_SIZE = WORD_SIZE >> 1;
     constexpr WordType HALF_MASK = ((WordType(1) << HALF_WORD_SIZE) - 1);
     // lower = smallest multiple of WORD_SIZE that is >= e.
@@ -1009,12 +1008,12 @@ private:
       BigInt subtractor = divider;
       int cur_bit = multiword::countl_zero(subtractor.val) -
                     multiword::countl_zero(remainder.val);
-      subtractor <<= static_cast<size_t>(cur_bit);
+      subtractor <<= cur_bit;
       for (; cur_bit >= 0 && remainder > 0; --cur_bit, subtractor >>= 1) {
         if (remainder < subtractor)
           continue;
         remainder -= subtractor;
-        quotient.set_bit(static_cast<size_t>(cur_bit));
+        quotient.set_bit(cur_bit);
       }
     }
     return Division{quotient, remainder};
@@ -1276,28 +1275,26 @@ rotr(T value, int rotate);
 template <typename T>
 [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<is_big_int_v<T>, T>
 rotl(T value, int rotate) {
-  constexpr int N = cpp::numeric_limits<T>::digits;
+  constexpr unsigned N = cpp::numeric_limits<T>::digits;
   rotate = rotate % N;
   if (!rotate)
     return value;
   if (rotate < 0)
     return cpp::rotr<T>(value, -rotate);
-  return (value << static_cast<size_t>(rotate)) |
-         (value >> (N - static_cast<size_t>(rotate)));
+  return (value << rotate) | (value >> (N - rotate));
 }
 
 // Specialization of cpp::rotr ('bit.h') for BigInt.
 template <typename T>
 [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<is_big_int_v<T>, T>
 rotr(T value, int rotate) {
-  constexpr int N = cpp::numeric_limits<T>::digits;
+  constexpr unsigned N = cpp::numeric_limits<T>::digits;
   rotate = rotate % N;
   if (!rotate)
     return value;
   if (rotate < 0)
     return cpp::rotl<T>(value, -rotate);
-  return (value >> static_cast<size_t>(rotate)) |
-         (value << (N - static_cast<size_t>(rotate)));
+  return (value >> rotate) | (value << (N - rotate));
 }
 
 } // namespace cpp
@@ -1314,7 +1311,7 @@ mask_trailing_ones() {
   T out; // zero initialized
   for (size_t i = 0; i <= QUOTIENT; ++i)
     out[i] = i < QUOTIENT
-                 ? cpp::numeric_limits<typename T::word_type>::max()
+                 ? -1
                  : mask_trailing_ones<typename T::word_type, REMAINDER>();
   return out;
 }
@@ -1330,7 +1327,7 @@ LIBC_INLINE constexpr cpp::enable_if_t<is_big_int_v<T>, T> mask_leading_ones() {
   T out; // zero initialized
   for (size_t i = QUOTIENT; i < T::WORD_COUNT; ++i)
     out[i] = i > QUOTIENT
-                 ? cpp::numeric_limits<typename T::word_type>::max()
+                 ? -1
                  : mask_leading_ones<typename T::word_type, REMAINDER>();
   return out;
 }
diff --git a/libc/src/__support/high_precision_decimal.h b/libc/src/__support/high_precision_decimal.h
index cb4b50c31544..922dce484aa6 100644
--- a/libc/src/__support/high_precision_decimal.h
+++ b/libc/src/__support/high_precision_decimal.h
@@ -264,7 +264,7 @@ private:
   LIBC_INLINE void left_shift(uint32_t shift_amount) {
     uint32_t new_digits = this->get_num_new_digits(shift_amount);
 
-    int32_t read_index = static_cast<int32_t>(this->num_digits - 1);
+    int32_t read_index = this->num_digits - 1;
     uint32_t write_index = this->num_digits + new_digits;
 
     uint64_t accumulator = 0;
@@ -329,7 +329,7 @@ public:
         if (saw_dot) {
           break;
         }
-        this->decimal_point = static_cast<int32_t>(total_digits);
+        this->decimal_point = total_digits;
         saw_dot = true;
       } else {
         if (num_string[num_cur] == '0' && this->num_digits == 0) {
@@ -350,7 +350,7 @@ public:
     }
 
     if (!saw_dot)
-      this->decimal_point = static_cast<int32_t>(total_digits);
+      this->decimal_point = total_digits;
 
     if (num_cur < num_len &&
         (num_string[num_cur] == 'e' || num_string[num_cur] == 'E')) {
@@ -393,7 +393,7 @@ public:
         this->left_shift(MAX_SHIFT_AMOUNT);
         shift_amount -= MAX_SHIFT_AMOUNT;
       }
-      this->left_shift(static_cast<uint32_t>(shift_amount));
+      this->left_shift(shift_amount);
     }
     // Right
     else {
@@ -401,7 +401,7 @@ public:
         this->right_shift(MAX_SHIFT_AMOUNT);
         shift_amount += MAX_SHIFT_AMOUNT;
       }
-      this->right_shift(static_cast<uint32_t>(-shift_amount));
+      this->right_shift(-shift_amount);
     }
   }
 
@@ -424,8 +424,8 @@ public:
       result *= 10;
       ++cur_digit;
     }
-    return result +
-           static_cast<T>(this->should_round_up(this->decimal_point, round));
+    return result + static_cast<unsigned int>(
+                        this->should_round_up(this->decimal_point, round));
   }
 
   // Extra functions for testing.
diff --git a/libc/src/__support/integer_literals.h b/libc/src/__support/integer_literals.h
index f68b7ef12c87..0298ec7d088d 100644
--- a/libc/src/__support/integer_literals.h
+++ b/libc/src/__support/integer_literals.h
@@ -47,7 +47,7 @@ LIBC_INLINE constexpr T accumulate(int base, const uint8_t *digits,
                                    size_t size) {
   T value{};
   for (; size; ++digits, --size) {
-    value *= static_cast<unsigned int>(base);
+    value *= base;
     value += *digits;
   }
   return value;
diff --git a/libc/src/__support/integer_to_string.h b/libc/src/__support/integer_to_string.h
index 65bdcf16b386..13dd83e9ed2b 100644
--- a/libc/src/__support/integer_to_string.h
+++ b/libc/src/__support/integer_to_string.h
@@ -405,7 +405,7 @@ template <typename T, typename Fmt = radix::Dec> class IntegerToString {
     // Returns the absolute value of 'value' as 'UNSIGNED_T'.
     LIBC_INLINE static UNSIGNED_T abs(T value) {
       if (cpp::is_unsigned_v<T> || value >= 0)
-        return static_cast<UNSIGNED_T>(value); // already of the right sign.
+        return value; // already of the right sign.
 
       // Signed integers are asymmetric (e.g., int8_t ∈ [-128, 127]).
       // Thus negating the type's minimum value would overflow.
@@ -422,8 +422,7 @@ template <typename T, typename Fmt = radix::Dec> class IntegerToString {
       if (value == cpp::numeric_limits<T>::min()) {
         return cpp::bit_cast<UNSIGNED_T>(value);
       } else {
-        return static_cast<UNSIGNED_T>(
-            -value); // legal and representable both as T and UNSIGNED_T.`
+        return -value; // legal and representable both as T and UNSIGNED_T.`
       }
     }
 
diff --git a/libc/src/__support/memory_size.h b/libc/src/__support/memory_size.h
index 3d40b113bcb6..cdd6a10222de 100644
--- a/libc/src/__support/memory_size.h
+++ b/libc/src/__support/memory_size.h
@@ -77,8 +77,7 @@ public:
     if (!cpp::has_single_bit(alignment) || alignment > MAX_MEM_SIZE || !valid())
       return SafeMemSize{type{-1}};
 
-    type offset =
-        static_cast<type>(offset_to(static_cast<size_t>(value), alignment));
+    type offset = offset_to(value, alignment);
 
     if (LIBC_UNLIKELY(offset > static_cast<type>(MAX_MEM_SIZE) - value))
       return SafeMemSize{type{-1}};
diff --git a/libc/src/__support/str_to_float.h b/libc/src/__support/str_to_float.h
index 48c88309c58e..b4d5646822df 100644
--- a/libc/src/__support/str_to_float.h
+++ b/libc/src/__support/str_to_float.h
@@ -108,11 +108,11 @@ eisel_lemire(ExpandedFloat<T> init_num,
   }
 
   // Normalization
-  uint32_t clz = static_cast<uint32_t>(cpp::countl_zero<StorageType>(mantissa));
+  uint32_t clz = cpp::countl_zero<StorageType>(mantissa);
   mantissa <<= clz;
 
-  int32_t exp2 = exp10_to_exp2(exp10) + FPBits::STORAGE_LEN + FPBits::EXP_BIAS -
-                 static_cast<int32_t>(clz);
+  int32_t exp2 =
+      exp10_to_exp2(exp10) + FPBits::STORAGE_LEN + FPBits::EXP_BIAS - clz;
 
   // Multiplication
   const uint64_t *power_of_ten =
@@ -225,8 +225,8 @@ eisel_lemire<long double>(ExpandedFloat<long double> init_num,
   }
 
   // Normalization
-  int32_t clz = static_cast<int32_t>(cpp::countl_zero(mantissa)) -
-                ((sizeof(UInt128) - sizeof(StorageType)) * CHAR_BIT);
+  uint32_t clz = cpp::countl_zero(mantissa) -
+                 ((sizeof(UInt128) - sizeof(StorageType)) * CHAR_BIT);
   mantissa <<= clz;
 
   int32_t exp2 =
@@ -802,7 +802,7 @@ LIBC_INLINE FloatConvertReturn<T> binary_exp_to_float(ExpandedFloat<T> init_num,
 
   // Handle subnormals.
   if (biased_exponent <= 0) {
-    amount_to_shift_right += static_cast<uint32_t>(1 - biased_exponent);
+    amount_to_shift_right += 1 - biased_exponent;
     biased_exponent = 0;
 
     if (amount_to_shift_right > FPBits::STORAGE_LEN) {
@@ -909,7 +909,7 @@ decimal_string_to_float(const char *__restrict src, const char DECIMAL_POINT,
       cpp::numeric_limits<StorageType>::max() / BASE;
   while (true) {
     if (isdigit(src[index])) {
-      uint32_t digit = static_cast<uint32_t>(b36_char_to_int(src[index]));
+      uint32_t digit = b36_char_to_int(src[index]);
       seen_digit = true;
 
       if (mantissa < bitstype_max_div_by_base) {
@@ -956,7 +956,7 @@ decimal_string_to_float(const char *__restrict src, const char DECIMAL_POINT,
       if (result.has_error())
         output.error = result.error;
       int32_t add_to_exponent = result.value;
-      index += static_cast<size_t>(result.parsed_len);
+      index += result.parsed_len;
 
       // Here we do this operation as int64 to avoid overflow.
       int64_t temp_exponent = static_cast<int64_t>(exponent) +
@@ -1020,7 +1020,7 @@ hexadecimal_string_to_float(const char *__restrict src,
       cpp::numeric_limits<StorageType>::max() / BASE;
   while (true) {
     if (isalnum(src[index])) {
-      uint32_t digit = static_cast<uint32_t>(b36_char_to_int(src[index]));
+      uint32_t digit = b36_char_to_int(src[index]);
       if (digit < BASE)
         seen_digit = true;
       else
@@ -1070,7 +1070,7 @@ hexadecimal_string_to_float(const char *__restrict src,
         output.error = result.error;
 
       int32_t add_to_exponent = result.value;
-      index += static_cast<size_t>(result.parsed_len);
+      index += result.parsed_len;
 
       // Here we do this operation as int64 to avoid overflow.
       int64_t temp_exponent = static_cast<int64_t>(exponent) +
@@ -1135,7 +1135,7 @@ LIBC_INLINE StrToNumResult<T> strtofloatingpoint(const char *__restrict src) {
 
   int error = 0;
 
-  size_t index = static_cast<size_t>(first_non_whitespace(src) - src);
+  ptrdiff_t index = first_non_whitespace(src) - src;
 
   if (src[index] == '+' || src[index] == '-') {
     sign = src[index];
@@ -1245,7 +1245,7 @@ LIBC_INLINE StrToNumResult<T> strtofloatingpoint(const char *__restrict src) {
   // special 80 bit long doubles. Otherwise it should be inlined out.
   set_implicit_bit<T>(result);
 
-  return {result.get_val(), static_cast<ptrdiff_t>(index), error};
+  return {result.get_val(), index, error};
 }
 
 template <class T> LIBC_INLINE StrToNumResult<T> strtonan(const char *arg) {
diff --git a/libc/src/__support/str_to_integer.h b/libc/src/__support/str_to_integer.h
index 9212ad25d082..8e569e8a7feb 100644
--- a/libc/src/__support/str_to_integer.h
+++ b/libc/src/__support/str_to_integer.h
@@ -96,7 +96,7 @@ strtointeger(const char *__restrict src, int base,
   if (base < 0 || base == 1 || base > 36)
     return {0, 0, EINVAL};
 
-  src_cur = static_cast<size_t>(first_non_whitespace(src, src_len) - src);
+  src_cur = first_non_whitespace(src, src_len) - src;
 
   char result_sign = '+';
   if (src[src_cur] == '+' || src[src_cur] == '-') {
@@ -119,7 +119,7 @@ strtointeger(const char *__restrict src, int base,
   ResultType const abs_max =
       (is_positive ? cpp::numeric_limits<T>::max() : NEGATIVE_MAX);
   ResultType const abs_max_div_by_base =
-      abs_max / static_cast<ResultType>(base);
+      static_cast<ResultType>(abs_max / base);
 
   while (src_cur < src_len && isalnum(src[src_cur])) {
     int cur_digit = b36_char_to_int(src[src_cur]);
@@ -141,17 +141,17 @@ strtointeger(const char *__restrict src, int base,
       result = abs_max;
       error_val = ERANGE;
     } else {
-      result = result * static_cast<ResultType>(base);
+      result = static_cast<ResultType>(result * base);
     }
-    if (result > abs_max - static_cast<ResultType>(cur_digit)) {
+    if (result > abs_max - cur_digit) {
       result = abs_max;
       error_val = ERANGE;
     } else {
-      result = result + static_cast<ResultType>(cur_digit);
+      result = static_cast<ResultType>(result + cur_digit);
     }
   }
 
-  ptrdiff_t str_len = is_number ? static_cast<ptrdiff_t>(src_cur) : 0;
+  ptrdiff_t str_len = is_number ? (src_cur) : 0;
 
   if (error_val == ERANGE) {
     if (is_positive || IS_UNSIGNED)
diff --git a/libc/src/stdio/printf_core/parser.h b/libc/src/stdio/printf_core/parser.h
index 89556f1a9e5f..acbbaa25b1c9 100644
--- a/libc/src/stdio/printf_core/parser.h
+++ b/libc/src/stdio/printf_core/parser.h
@@ -57,8 +57,7 @@ template <typename T> using int_type_of_v = typename int_type_of<T>::type;
     if (!temp.has_value()) {                                                   \
       section.has_conv = false;                                                \
     } else {                                                                   \
-      dst = static_cast<decltype(dst)>(                                        \
-          cpp::bit_cast<int_type_of_v<arg_type>>(temp.value()));               \
+      dst = cpp::bit_cast<int_type_of_v<arg_type>>(temp.value());              \
     }                                                                          \
   }
 #else
@@ -131,7 +130,7 @@ public:
       } else if (internal::isdigit(str[cur_pos])) {
         auto result = internal::strtointeger<int>(str + cur_pos, 10);
         section.min_width = result.value;
-        cur_pos = cur_pos + static_cast<size_t>(result.parsed_len);
+        cur_pos = cur_pos + result.parsed_len;
       }
       if (section.min_width < 0) {
         section.min_width =
@@ -154,7 +153,7 @@ public:
         } else if (internal::isdigit(str[cur_pos])) {
           auto result = internal::strtointeger<int>(str + cur_pos, 10);
           section.precision = result.value;
-          cur_pos = cur_pos + static_cast<size_t>(result.parsed_len);
+          cur_pos = cur_pos + result.parsed_len;
         }
       }
 
@@ -266,8 +265,7 @@ public:
       case ('m'):
         // %m is an odd conversion in that it doesn't consume an argument, it
         // just takes the current value of errno as its argument.
-        section.conv_val_raw =
-            static_cast<fputil::FPBits<double>::StorageType>(libc_errno);
+        section.conv_val_raw = static_cast<int>(libc_errno);
         break;
 #endif // LIBC_COPT_PRINTF_DISABLE_STRERROR
 #ifndef LIBC_COPT_PRINTF_DISABLE_WRITE_INT
@@ -358,7 +356,7 @@ private:
       }
       if (internal::isdigit(str[*local_pos])) {
         const auto result = internal::strtointeger<int>(str + *local_pos, 10);
-        *local_pos += static_cast<size_t>(result.parsed_len);
+        *local_pos += result.parsed_len;
         return {lm, static_cast<size_t>(cpp::max(0, result.value))};
       }
       return {lm, 0};
@@ -407,10 +405,10 @@ private:
   LIBC_INLINE size_t parse_index(size_t *local_pos) {
     if (internal::isdigit(str[*local_pos])) {
       auto result = internal::strtointeger<int>(str + *local_pos, 10);
-      size_t index = static_cast<size_t>(result.value);
-      if (str[*local_pos + static_cast<size_t>(result.parsed_len)] != '$')
+      size_t index = result.value;
+      if (str[*local_pos + result.parsed_len] != '$')
         return 0;
-      *local_pos = static_cast<size_t>(1 + result.parsed_len) + *local_pos;
+      *local_pos = 1 + result.parsed_len + *local_pos;
       return index;
     }
     return 0;
diff --git a/libc/src/stdio/printf_core/writer.h b/libc/src/stdio/printf_core/writer.h
index 28c9a2827087..5526a478ea62 100644
--- a/libc/src/stdio/printf_core/writer.h
+++ b/libc/src/stdio/printf_core/writer.h
@@ -135,8 +135,7 @@ public:
     chars_written += static_cast<int>(length);
 
     if (LIBC_LIKELY(wb->buff_cur + length <= wb->buff_len)) {
-      inline_memset(wb->buff + wb->buff_cur,
-                    static_cast<unsigned char>(new_char), length);
+      inline_memset(wb->buff + wb->buff_cur, new_char, length);
       wb->buff_cur += length;
       return WRITE_OK;
     }
diff --git a/libc/src/stdio/scanf_core/parser.h b/libc/src/stdio/scanf_core/parser.h
index 1e2f26e0d3fd..6cc5b30eb0db 100644
--- a/libc/src/stdio/scanf_core/parser.h
+++ b/libc/src/stdio/scanf_core/parser.h
@@ -78,7 +78,7 @@ public:
       if (internal::isdigit(str[cur_pos])) {
         auto result = internal::strtointeger<int>(str + cur_pos, 10);
         section.max_width = result.value;
-        cur_pos = cur_pos + static_cast<size_t>(result.parsed_len);
+        cur_pos = cur_pos + result.parsed_len;
       }
 
       // TODO(michaelrj): add posix allocate flag support.
@@ -150,11 +150,10 @@ public:
             char b = str[cur_pos + 1];
             char start = (a < b ? a : b);
             char end = (a < b ? b : a);
-            scan_set.set_range(static_cast<size_t>(start),
-                               static_cast<size_t>(end));
+            scan_set.set_range(start, end);
             cur_pos += 2;
           } else {
-            scan_set.set(static_cast<size_t>(str[cur_pos]));
+            scan_set.set(str[cur_pos]);
             ++cur_pos;
           }
         }
@@ -238,10 +237,10 @@ private:
   LIBC_INLINE size_t parse_index(size_t *local_pos) {
     if (internal::isdigit(str[*local_pos])) {
       auto result = internal::strtointeger<int>(str + *local_pos, 10);
-      size_t index = static_cast<size_t>(result.value);
-      if (str[*local_pos + static_cast<size_t>(result.parsed_len)] != '$')
+      size_t index = result.value;
+      if (str[*local_pos + result.parsed_len] != '$')
         return 0;
-      *local_pos = static_cast<size_t>(1 + result.parsed_len) + *local_pos;
+      *local_pos = 1 + result.parsed_len + *local_pos;
       return index;
     }
     return 0;
diff --git a/libc/src/stdlib/quick_sort.h b/libc/src/stdlib/quick_sort.h
index 8ba0098854d1..9ab283025001 100644
--- a/libc/src/stdlib/quick_sort.h
+++ b/libc/src/stdlib/quick_sort.h
@@ -167,9 +167,7 @@ LIBC_INLINE void quick_sort_impl(A &array, const void *ancestor_pivot,
   }
 }
 
-constexpr size_t ilog2(size_t n) {
-  return static_cast<size_t>(cpp::bit_width(n)) - 1;
-}
+constexpr size_t ilog2(size_t n) { return cpp::bit_width(n) - 1; }
 
 template <typename A, typename F>
 LIBC_INLINE void quick_sort(A &array, const F &is_less) {
diff --git a/libc/src/string/memory_utils/utils.h b/libc/src/string/memory_utils/utils.h
index 508a70794211..5c9bc72208f8 100644
--- a/libc/src/string/memory_utils/utils.h
+++ b/libc/src/string/memory_utils/utils.h
@@ -263,7 +263,7 @@ LIBC_INLINE void store_aligned(ValueType value, Ptr dst) {
   static_assert(sizeof(ValueType) >= (sizeof(T) + ... + sizeof(TS)));
   constexpr size_t SHIFT = sizeof(T) * 8;
   if constexpr (Endian::IS_LITTLE) {
-    store<T>(assume_aligned<sizeof(T)>(dst), T(value & T(~0)));
+    store<T>(assume_aligned<sizeof(T)>(dst), value & ~T(0));
     if constexpr (sizeof...(TS) > 0)
       store_aligned<ValueType, TS...>(value >> SHIFT, dst + sizeof(T));
   } else if constexpr (Endian::IS_BIG) {
@@ -293,7 +293,7 @@ LIBC_INLINE void store64_aligned(uint64_t value, Ptr dst, size_t offset) {
 // Advances the pointers p1 and p2 by offset bytes and decrease count by the
 // same amount.
 template <typename T1, typename T2>
-LIBC_INLINE void adjust(uintptr_t offset, T1 *__restrict &p1,
+LIBC_INLINE void adjust(ptrdiff_t offset, T1 *__restrict &p1,
                         T2 *__restrict &p2, size_t &count) {
   p1 += offset;
   p2 += offset;
diff --git a/libc/src/string/string_utils.h b/libc/src/string/string_utils.h
index e4659f65c93e..583d35014d39 100644
--- a/libc/src/string/string_utils.h
+++ b/libc/src/string/string_utils.h
@@ -66,7 +66,7 @@ LIBC_INLINE size_t string_length_wide_read(const char *src) {
   for (; reinterpret_cast<uintptr_t>(char_ptr) % sizeof(Word) != 0;
        ++char_ptr) {
     if (*char_ptr == '\0')
-      return static_cast<size_t>(char_ptr - src);
+      return char_ptr - src;
   }
   // Step 2: read blocks
   for (const Word *block_ptr = reinterpret_cast<const Word *>(char_ptr);
@@ -77,7 +77,7 @@ LIBC_INLINE size_t string_length_wide_read(const char *src) {
   for (; *char_ptr != '\0'; ++char_ptr) {
     ;
   }
-  return static_cast<size_t>(char_ptr - src);
+  return char_ptr - src;
 }
 
 // Returns the length of a string, denoted by the first occurrence
@@ -169,7 +169,7 @@ LIBC_INLINE size_t complementary_span(const char *src, const char *segment) {
   for (; *src && !bitset.test(*reinterpret_cast<const unsigned char *>(src));
        ++src)
     ;
-  return static_cast<size_t>(src - initial);
+  return src - initial;
 }
 
 // Given the similarities between strtok and strtok_r, we can implement both
@@ -189,14 +189,12 @@ LIBC_INLINE char *string_token(char *__restrict src,
   if (LIBC_UNLIKELY(src == nullptr && ((src = *saveptr) == nullptr)))
     return nullptr;
 
-  static_assert(sizeof(char) == sizeof(cpp::byte),
-                "bitset of 256 assumes char is 8 bits");
   cpp::bitset<256> delimiter_set;
   for (; *delimiter_string != '\0'; ++delimiter_string)
-    delimiter_set.set(static_cast<size_t>(*delimiter_string));
+    delimiter_set.set(*delimiter_string);
 
   if constexpr (SkipDelim)
-    for (; *src != '\0' && delimiter_set.test(static_cast<size_t>(*src)); ++src)
+    for (; *src != '\0' && delimiter_set.test(*src); ++src)
       ;
   if (*src == '\0') {
     *saveptr = src;
@@ -204,7 +202,7 @@ LIBC_INLINE char *string_token(char *__restrict src,
   }
   char *token = src;
   for (; *src != '\0'; ++src) {
-    if (delimiter_set.test(static_cast<size_t>(*src))) {
+    if (delimiter_set.test(*src)) {
       *src = '\0';
       ++src;
       break;