fix(od):fix GNU coreutils test od float.sh (#9534)

* feat: add compact float formatting for half and bfloat16 in od

Implement trim_float_repr() to remove trailing zeros from float strings while preserving signs and exponents, and pad_float_repr() to align trimmed floats to fixed width. Update format_item_f16() and format_item_bf16() to produce compact output matching GNU od. Add regression tests for float16 and bfloat16 compact printing.

* refactor(od): format multiline format! in format_item_bf16 for readability

Reformat the format! macro call in the format_item_bf16 function in prn_float.rs
to span multiple lines, improving code readability without changing functionality.

* fix(od): preserve canonical precision for f16/bf16 float formats

Remove trimming of trailing zeros from f16 and bf16 float representations
in od output to maintain original precision and align behavior with
f32/f64 formatters, ensuring stable output across platforms. Update
corresponding tests to reflect the change in expected output.

* refactor(od): simplify float padding format and update tests

- Remove redundant `width = width` parameter from `format!` macro in `pad_float_repr`
- Add "bfloat" to spell-checker ignore list for better test coverage on bf16 format

* feat(od): trim trailing zeros in float outputs for GNU compatibility

Add `trim_trailing_zeros` function to remove trailing zeros and redundant decimal points from formatted floats, ensuring compact output matching GNU od for f16 and bf16 types. Update `format_item_f16` and `format_item_bf16` to apply trimming before padding.

* fix: preserve trailing zeros in F16 and BF16 float formats to match GNU od output

Remove the `trim_trailing_zeros` function and update `format_item_f16` and `format_item_bf16` to keep the raw formatted strings without trimming trailing zeros. This ensures consistent column widths and aligns with GNU od behavior for 16-bit float representations, preventing misalignment in output tables.

* refactor(od/prn_float): combine multiline format! into single line in format_item_f16

The format! macro call in format_item_f16 was split across multiple lines with newlines. This change consolidates it into a single line for improved code readability and consistency with similar patterns in the file, without altering the function's output or logic.

* feat(od): trim trailing zeros in half-precision and bfloat16 float outputs

- Add `trim_float_repr` function to remove unnecessary trailing zeros and padding from normalized float strings, leaving exponents unchanged.
- Update `format_item_f16` and `format_item_bf16` to apply trimming while maintaining column alignment via re-padding.
- Update test expectations to reflect the more compact float representations (e.g., "1" instead of "1.0000000").

* refactor: simplify float trimming condition in prn_float.rs

Replace `if let Some(_) = s.find('.')` with `s.find('.').is_some()` in the `trim_float_repr` function to improve code clarity and idiomatic Rust usage while maintaining the same logic for checking decimal presence=black.

* Update src/uu/od/src/prn_float.rs

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

---------

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

src/uu/od/src/prn_float.rs

@@ -37,8 +37,61 @@ pub static FORMAT_ITEM_BF16: FormatterItemInfo = FormatterItemInfo {
     formatter: FormatWriter::BFloatWriter(format_item_bf16),
 };
 
+/// Clean up a normalized float string by removing unnecessary padding and digits.
+/// - Strip leading spaces.
+/// - Trim trailing zeros after the decimal point (and the dot itself if empty).
+/// - Leave the exponent part (e/E...) untouched.
+fn trim_float_repr(raw: &str) -> String {
+    // Drop padding added by `format!` width specification
+    let mut s = raw.trim_start().to_string();
+
+    // Keep NaN/Inf representations as-is
+    let lower = s.to_ascii_lowercase();
+    if lower == "nan" || lower == "inf" || lower == "-inf" {
+        return s;
+    }
+
+    // Separate exponent from mantissa
+    let mut exp_part = String::new();
+    if let Some(idx) = s.find(['e', 'E']) {
+        exp_part = s[idx..].to_string();
+        s.truncate(idx);
+    }
+
+    // Trim trailing zeros in mantissa, then remove trailing dot if left alone
+    if s.contains('.') {
+        while s.ends_with('0') {
+            s.pop();
+        }
+        if s.ends_with('.') {
+            s.pop();
+        }
+    }
+
+    // If everything was trimmed, leave a single zero
+    if s.is_empty() || s == "-" || s == "+" {
+        s.push('0');
+    }
+
+    s.push_str(&exp_part);
+    s
+}
+
+/// Pad a floating value to a fixed width for column alignment while keeping
+/// the original precision (including trailing zeros). This mirrors the
+/// behavior of other float formatters (`f32`, `f64`) and keeps the output
+/// stable across platforms.
+fn pad_float_repr(raw: &str, width: usize) -> String {
+    format!("{raw:>width$}")
+}
+
 pub fn format_item_f16(f: f64) -> String {
-    format!(" {}", format_f16(f16::from_f64(f)))
+    let value = f16::from_f64(f);
+    let width = FORMAT_ITEM_F16.print_width - 1;
+    // Format once, trim redundant zeros, then re-pad to the canonical width
+    let raw = format_f16(value);
+    let trimmed = trim_float_repr(&raw);
+    format!(" {}", pad_float_repr(&trimmed, width))
 }
 
 pub fn format_item_f32(f: f64) -> String {
@@ -82,7 +135,10 @@ fn format_f64_exp_precision(f: f64, width: usize, precision: usize) -> String {
 
 pub fn format_item_bf16(f: f64) -> String {
     let bf = bf16::from_f32(f as f32);
-    format!(" {}", format_binary16_like(f, 15, 8, is_subnormal_bf16(bf)))
+    let width = FORMAT_ITEM_BF16.print_width - 1;
+    let raw = format_binary16_like(f64::from(bf), width, 8, is_subnormal_bf16(bf));
+    let trimmed = trim_float_repr(&raw);
+    format!(" {}", pad_float_repr(&trimmed, width))
 }
 
 fn format_f16(f: f16) -> String {

tests/by-util/test_od.rs

@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore abcdefghijklmnopqrstuvwxyz Anone fdbb littl
+// spell-checker:ignore abcdefghijklmnopqrstuvwxyz Anone fdbb littl bfloat
 
 #[cfg(unix)]
 use std::io::Read;
@@ -197,6 +197,32 @@ fn test_hex32() {
         .stdout_only(expected_output);
 }
 
+// Regression: 16-bit IEEE half should print with canonical precision (no spurious digits)
+#[test]
+fn test_float16_compact() {
+    let input: [u8; 4] = [0x3c, 0x00, 0x3c, 0x00]; // two times 1.0 in big-endian half
+    new_ucmd!()
+        .arg("--endian=big")
+        .arg("-An")
+        .arg("-tfH")
+        .run_piped_stdin(&input[..])
+        .success()
+        .stdout_only("               1               1\n");
+}
+
+// Regression: 16-bit bfloat should print with canonical precision (no spurious digits)
+#[test]
+fn test_bfloat16_compact() {
+    let input: [u8; 4] = [0x3f, 0x80, 0x3f, 0x80]; // two times 1.0 in big-endian bfloat16
+    new_ucmd!()
+        .arg("--endian=big")
+        .arg("-An")
+        .arg("-tfB")
+        .run_piped_stdin(&input[..])
+        .success()
+        .stdout_only("               1               1\n");
+}
+
 #[test]
 fn test_f16() {
     let input: [u8; 14] = [
@@ -210,7 +236,7 @@ fn test_f16() {
     ]; // 0x8400 -6.104e-5
     let expected_output = unindent(
         "
-            0000000       1.0000000               0              -0             inf
+            0000000               1               0              -0             inf
             0000010            -inf             NaN   -6.1035156e-5
             0000016
             ",
@@ -237,7 +263,7 @@ fn test_fh() {
     ]; // 0x8400 -6.1035156e-5
     let expected_output = unindent(
         "
-            0000000       1.0000000               0              -0             inf
+            0000000               1               0              -0             inf
             0000010            -inf             NaN   -6.1035156e-5
             0000016
         ",
@@ -264,7 +290,7 @@ fn test_fb() {
     ]; // -6.1035156e-5
     let expected_output = unindent(
         "
-            0000000       1.0000000               0              -0             inf
+            0000000               1               0              -0             inf
             0000010            -inf             NaN   -6.1035156e-5
             0000016
         ",