[libc] Add -Wno-sign-conversion & re-attempt -Wconversion (#129811)

Relates to
#119281 (comment)

Author: vinay-deshmukh

libc/CMakeLists.txt

@@ -34,6 +34,7 @@ if (CMAKE_BUILD_TYPE STREQUAL "Debug")
   add_definitions("-D_DEBUG")
 endif()
 
+
 # Default to C++17
 set(CMAKE_CXX_STANDARD 17)
 

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -36,8 +36,9 @@ function(_get_common_test_compile_options output_var c_test flags)
     if(NOT LIBC_WNO_ERROR)
       # list(APPEND compile_options "-Werror")
     endif()
-    # list(APPEND compile_options "-Wconversion")
-    # list(APPEND compile_options "-Wno-sign-conversion")
+    list(APPEND compile_options "-Wconversion")
+    # FIXME: convert to -Wsign-conversion
+    list(APPEND compile_options "-Wno-sign-conversion")
     list(APPEND compile_options "-Wimplicit-fallthrough")
     list(APPEND compile_options "-Wwrite-strings")
     # Silence this warning because _Complex is a part of C99.

libc/src/__support/CPP/bit.h

@@ -101,7 +101,7 @@ countr_zero(T value) {
     shift >>= 1;
     mask >>= shift;
   }
-  return zero_bits;
+  return static_cast<int>(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 zero_bits;
+  return static_cast<int>(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 unsigned N = cpp::numeric_limits<T>::digits;
+  constexpr int 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 unsigned N = cpp::numeric_limits<T>::digits;
+  constexpr int N = cpp::numeric_limits<T>::digits;
   rotate = rotate % N;
   if (!rotate)
     return value;

libc/src/__support/CPP/span.h

@@ -11,6 +11,7 @@
 #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
 
@@ -48,7 +49,8 @@ template <typename T> class span {
   using const_reference = const T &;
   using iterator = T *;
 
-  LIBC_INLINE_VAR static constexpr size_type dynamic_extent = -1;
+  LIBC_INLINE_VAR static constexpr size_type dynamic_extent =
+      cpp::numeric_limits<size_type>::max();
 
   LIBC_INLINE constexpr span() : span_data(nullptr), span_size(0) {}
 
@@ -58,7 +60,7 @@ template <typename T> class span {
       : span_data(first), span_size(count) {}
 
   LIBC_INLINE constexpr span(pointer first, pointer end)
-      : span_data(first), span_size(end - first) {}
+      : span_data(first), span_size(static_cast<size_t>(end - first)) {}
 
   template <typename U, size_t N,
             cpp::enable_if_t<is_compatible_v<U>, bool> = true>

libc/src/__support/CPP/string.h

@@ -67,7 +67,8 @@ class string {
       : string(cstr, ::LIBC_NAMESPACE::internal::string_length(cstr)) {}
   LIBC_INLINE string(size_t size_, char value) {
     resize(size_);
-    inline_memset((void *)buffer_, value, size_);
+    static_assert(sizeof(char) == sizeof(uint8_t));
+    inline_memset((void *)buffer_, static_cast<uint8_t>(value), size_);
   }
 
   LIBC_INLINE string &operator=(const string &other) {

libc/src/__support/CPP/string_view.h

@@ -9,6 +9,7 @@
 #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"
 
@@ -40,7 +41,7 @@ class string_view {
   LIBC_INLINE static constexpr size_t length(const char *Str) {
     for (const char *End = Str;; ++End)
       if (*End == '\0')
-        return End - Str;
+        return static_cast<size_t>(End - Str);
   }
 
   LIBC_INLINE bool equals(string_view Other) const {
@@ -61,7 +62,8 @@ class string_view {
 
   // special value equal to the maximum value representable by the type
   // size_type.
-  LIBC_INLINE_VAR static constexpr size_t npos = -1;
+  LIBC_INLINE_VAR static constexpr size_t npos =
+      cpp::numeric_limits<size_t>::max();
 
   LIBC_INLINE constexpr string_view() : Data(nullptr), Len(0) {}
 

libc/src/__support/FPUtil/FPBits.h

@@ -247,11 +247,11 @@ template <FPType fp_type> struct FPStorage : public FPLayout<fp_type> {
     using UP::UP;
 
     LIBC_INLINE constexpr BiasedExponent(Exponent exp)
-        : UP(static_cast<int32_t>(exp) + EXP_BIAS) {}
+        : UP(static_cast<uint32_t>(static_cast<int32_t>(exp) + EXP_BIAS)) {}
 
     // Cast operator to get convert from BiasedExponent to Exponent.
     LIBC_INLINE constexpr operator Exponent() const {
-      return Exponent(UP::value - EXP_BIAS);
+      return Exponent(static_cast<int32_t>(UP::value - EXP_BIAS));
     }
 
     LIBC_INLINE constexpr BiasedExponent &operator++() {
@@ -686,7 +686,7 @@ struct FPRepImpl : public FPRepSem<fp_type, RetT> {
   }
 
   LIBC_INLINE constexpr void set_biased_exponent(StorageType biased) {
-    UP::set_biased_exponent(BiasedExponent((int32_t)biased));
+    UP::set_biased_exponent(BiasedExponent(static_cast<uint32_t>(biased)));
   }
 
   LIBC_INLINE constexpr int get_exponent() const {

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 = SUBNORMAL_EXPONENT - exponent;
+      unsigned shift = static_cast<unsigned>(SUBNORMAL_EXPONENT - exponent);
       // Since exponent > subnormalExponent, shift is strictly greater than
       // zero.
       if (shift <= FPBits<T>::FRACTION_LEN + 1) {
@@ -160,7 +160,7 @@ template <typename T> struct NormalFloat {
     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 - shift;
+      exponent = 1 - FPBits<T>::EXP_BIAS - static_cast<int32_t>(shift);
     } else {
       exponent = bits.get_biased_exponent() - FPBits<T>::EXP_BIAS;
       mantissa = ONE | bits.get_mantissa();

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(oldExcepts);
+  return FEnv::exceptionStatusToMacro(static_cast<uint32_t>(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(oldExcepts);
+  return FEnv::exceptionStatusToMacro(static_cast<uint32_t>(oldExcepts));
 }
 
 LIBC_INLINE int get_except() {
   uint32_t controlWord = FEnv::getControlWord();
-  int enabledExcepts =
+  uint32_t enabledExcepts =
       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
   return FEnv::exceptionStatusToMacro(enabledExcepts);
 }
@@ -250,8 +250,10 @@ LIBC_INLINE int set_round(int mode) {
   }
 
   uint32_t controlWord = FEnv::getControlWord();
-  controlWord &= ~(0x3 << FEnv::RoundingControlBitPosition);
-  controlWord |= (bitValue << FEnv::RoundingControlBitPosition);
+  controlWord &=
+      static_cast<uint32_t>(~(0x3 << FEnv::RoundingControlBitPosition));
+  controlWord |=
+      static_cast<uint32_t>(bitValue << FEnv::RoundingControlBitPosition);
   FEnv::writeControlWord(controlWord);
 
   return 0;

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(int status) {
+  LIBC_INLINE static uint32_t exception_value_from_status(uint32_t 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(int control) {
+  LIBC_INLINE static uint32_t exception_value_from_control(uint32_t 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 int exception_value_to_status(uint32_t excepts) {
+  LIBC_INLINE static uint32_t 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 int exception_value_to_control(uint32_t excepts) {
+  LIBC_INLINE static uint32_t 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) |
@@ -113,48 +113,54 @@ struct FEnv {
 };
 
 LIBC_INLINE int enable_except(int excepts) {
-  uint32_t new_excepts = FEnv::exception_value_from_status(excepts);
+  uint32_t new_excepts =
+      FEnv::exception_value_from_status(static_cast<uint32_t>(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 FEnv::exception_value_to_status(old_excepts);
+  return static_cast<int>(FEnv::exception_value_to_status(old_excepts));
 }
 
 LIBC_INLINE int disable_except(int excepts) {
-  uint32_t disabled_excepts = FEnv::exception_value_from_status(excepts);
+  uint32_t disabled_excepts =
+      FEnv::exception_value_from_status(static_cast<uint32_t>(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 FEnv::exception_value_to_status(old_excepts);
+  return static_cast<int>(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 FEnv::exception_value_to_status(enabled_excepts);
+  return static_cast<int>(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(excepts);
+  uint32_t except_value =
+      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
   status_word &= ~FEnv::exception_value_to_status(except_value);
   FEnv::set_status_word(status_word);
   return 0;
 }
 
 LIBC_INLINE int test_except(int excepts) {
   uint32_t statusWord = FEnv::get_status_word();
-  uint32_t ex_value = FEnv::exception_value_from_status(excepts);
-  return statusWord & FEnv::exception_value_to_status(ex_value);
+  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));
 }
 
 LIBC_INLINE int set_except(int excepts) {
   uint32_t status_word = FEnv::get_status_word();
-  uint32_t new_exceptions = FEnv::exception_value_from_status(excepts);
+  uint32_t new_exceptions =
+      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
   status_word |= FEnv::exception_value_to_status(new_exceptions);
   FEnv::set_status_word(status_word);
   return 0;
@@ -174,7 +180,8 @@ LIBC_INLINE int raise_except(int excepts) {
                          : "s0", "s1" /* s0 and s1 are clobbered */);
   };
 
-  uint32_t to_raise = FEnv::exception_value_from_status(excepts);
+  uint32_t to_raise =
+      FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
   int result = 0;
 
   if (to_raise & FEnv::EX_INVALID) {
@@ -237,7 +244,7 @@ LIBC_INLINE int get_round() {
 }
 
 LIBC_INLINE int set_round(int mode) {
-  uint16_t bit_value;
+  uint32_t bit_value;
   switch (mode) {
   case FE_TONEAREST:
     bit_value = FEnv::TONEAREST;
@@ -256,7 +263,7 @@ LIBC_INLINE int set_round(int mode) {
   }
 
   uint32_t control_word = FEnv::get_control_word();
-  control_word &= ~(0x3 << FEnv::ROUNDING_CONTROL_BIT_POSITION);
+  control_word &= ~(0x3u << FEnv::ROUNDING_CONTROL_BIT_POSITION);
   control_word |= (bit_value << FEnv::ROUNDING_CONTROL_BIT_POSITION);
   FEnv::set_control_word(control_word);