address more comments

Author: michaelrj-google

libc/src/__support/UInt.h

@@ -27,6 +27,11 @@ namespace LIBC_NAMESPACE::cpp {
 
 template <size_t Bits, bool Signed> struct BigInt {
 
+  // This being hardcoded as 64 is okay because we're using uint64_t as our
+  // internal type which will always be 64 bits.
+  LIBC_INLINE_VAR static constexpr size_t WORD_SIZE = 64;
+
+  // TODO: Replace references to 64 with WORD_SIZE.
   static_assert(Bits > 0 && Bits % 64 == 0,
                 "Number of bits in BigInt should be a multiple of 64.");
   LIBC_INLINE_VAR static constexpr size_t WORDCOUNT = Bits / 64;

libc/src/__support/float_to_string.h

@@ -670,8 +670,8 @@ template <> class FloatToString<long double> {
   LIBC_INLINE static constexpr void zero_leading_digits(
       cpp::UInt<FLOAT_AS_INT_WIDTH + EXTRA_INT_WIDTH> &int_num) {
     // 64 is the width of the numbers used to internally represent the UInt
-    for (size_t i = 0; i < EXTRA_INT_WIDTH / 64; ++i) {
-      int_num[i + (FLOAT_AS_INT_WIDTH / 64)] = 0;
+    for (size_t i = 0; i < EXTRA_INT_WIDTH / int_num.WORD_SIZE; ++i) {
+      int_num[i + (FLOAT_AS_INT_WIDTH / int_num.WORD_SIZE)] = 0;
     }
   }
 
@@ -809,10 +809,14 @@ template <> class FloatToString<long double> {
     // If we're currently after the requested block (remember these are
     // negative indices) we reset the number to the start. This is only
     // likely to happen in %g calls. This will also reset int_block_index.
-    if (block_index > int_block_index) {
-      init_convert();
-    }
-
+    // if (block_index > int_block_index) {
+    //   init_convert();
+    // }
+
+    // Printf is the only existing user of this code and it will only ever move
+    // downwards, except for %g but that currently creates a second
+    // float_to_string object so this assertion still holds. If a new user needs
+    // the ability to step backwards, uncomment the code above.
     LIBC_ASSERT(block_index <= int_block_index);
 
     // If we are currently before the requested block. Step until we reach the

libc/test/src/stdio/sprintf_test.cpp

@@ -2985,6 +2985,9 @@ TEST_F(LlvmLibcSPrintfTest, FloatAutoLongDoubleConv) {
   written = LIBC_NAMESPACE::sprintf(buff, "%Lg", 0xa.aaaaaaaaaaaaaabp-7L);
   ASSERT_STREQ_LEN(written, buff, "0.0833333");
 
+  written = LIBC_NAMESPACE::sprintf(buff, "%Lg", 9.99999999999e-100L);
+  ASSERT_STREQ_LEN(written, buff, "1e-99");
+
 #endif // LIBC_LONG_DOUBLE_IS_X86_FLOAT80
 
   // TODO: Uncomment the below tests after long double support is added