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[libc] Fix incorrect unsigned comparison (#135595)

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There is a problem with such unsigned comparison pattern:
```
if(unsigned_a - unsigned_b > 0) { /* only NOT go here when unsigned_a==unsigned_b */ }
```
When `unsigned_a` < `unsigned_b`, the result will still be `>0` due to
underflow.
This patch fixes two of the occurrences I found.
Also remove two redundant `if` where its condition is guaranteed by
outer `if`.
This commit is contained in:
Wu Yingcong
2025-04-17 09:33:48 +08:00
committed by GitHub
parent 6d8bf3cf3d
commit 6b8d072cfd
1 changed files with 7 additions and 9 deletions
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16
libc/src/stdio/printf_core/float_dec_converter.h
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@@ -186,13 +186,12 @@ template <WriteMode write_mode> class FloatWriter {
if (total_digits_written < digits_before_decimal &&
total_digits_written + buffered_digits >= digits_before_decimal &&
has_decimal_point) {
// digits_to_write > 0 guaranteed by outer if
size_t digits_to_write = digits_before_decimal - total_digits_written;
if (digits_to_write > 0) {
// Write the digits before the decimal point.
RET_IF_RESULT_NEGATIVE(writer->write({block_buffer, digits_to_write}));
}
// Write the digits before the decimal point.
RET_IF_RESULT_NEGATIVE(writer->write({block_buffer, digits_to_write}));
RET_IF_RESULT_NEGATIVE(writer->write(DECIMAL_POINT));
if (buffered_digits - digits_to_write > 0) {
if (buffered_digits > digits_to_write) {
// Write the digits after the decimal point.
RET_IF_RESULT_NEGATIVE(
writer->write({block_buffer + digits_to_write,
@@ -217,12 +216,11 @@ template <WriteMode write_mode> class FloatWriter {
total_digits_written + BLOCK_SIZE * max_block_count >=
digits_before_decimal &&
has_decimal_point) {
// digits_to_write > 0 guaranteed by outer if
size_t digits_to_write = digits_before_decimal - total_digits_written;
if (digits_to_write > 0) {
RET_IF_RESULT_NEGATIVE(writer->write(MAX_BLOCK_DIGIT, digits_to_write));
}
RET_IF_RESULT_NEGATIVE(writer->write(MAX_BLOCK_DIGIT, digits_to_write));
RET_IF_RESULT_NEGATIVE(writer->write(DECIMAL_POINT));
if ((BLOCK_SIZE * max_block_count) - digits_to_write > 0) {
if ((BLOCK_SIZE * max_block_count) > digits_to_write) {
RET_IF_RESULT_NEGATIVE(writer->write(
MAX_BLOCK_DIGIT, (BLOCK_SIZE * max_block_count) - digits_to_write));
}