printf: negative asterisk param changes alignment

src/uucore/src/lib/features/format/spec.rs

@@ -314,29 +314,36 @@ impl Spec {
     ) -> Result<(), FormatError> {
         match self {
             Self::Char { width, align_left } => {
-                let width = resolve_asterisk(*width, &mut args)?.unwrap_or(0);
-                write_padded(writer, &[args.get_char()], width, *align_left)
+                let (width, neg_width) =
+                    resolve_asterisk_maybe_negative(*width, &mut args).unwrap_or_default();
+                write_padded(writer, &[args.get_char()], width, *align_left || neg_width)
             }
             Self::String {
                 width,
                 align_left,
                 precision,
             } => {
-                let width = resolve_asterisk(*width, &mut args)?.unwrap_or(0);
+                let (width, neg_width) =
+                    resolve_asterisk_maybe_negative(*width, &mut args).unwrap_or_default();
 
                 // GNU does do this truncation on a byte level, see for instance:
                 //     printf "%.1s" 🙃
                 //     > �
                 // For now, we let printf panic when we truncate within a code point.
                 // TODO: We need to not use Rust's formatting for aligning the output,
                 // so that we can just write bytes to stdout without panicking.
-                let precision = resolve_asterisk(*precision, &mut args)?;
+                let precision = resolve_asterisk(*precision, &mut args);
                 let s = args.get_str();
                 let truncated = match precision {
                     Some(p) if p < s.len() => &s[..p],
                     _ => s,
                 };
-                write_padded(writer, truncated.as_bytes(), width, *align_left)
+                write_padded(
+                    writer,
+                    truncated.as_bytes(),
+                    width,
+                    *align_left || neg_width,
+                )
             }
             Self::EscapedString => {
                 let s = args.get_str();
@@ -374,8 +381,8 @@ impl Spec {
                 positive_sign,
                 alignment,
             } => {
-                let width = resolve_asterisk(*width, &mut args)?.unwrap_or(0);
-                let precision = resolve_asterisk(*precision, &mut args)?.unwrap_or(0);
+                let width = resolve_asterisk(*width, &mut args).unwrap_or(0);
+                let precision = resolve_asterisk(*precision, &mut args).unwrap_or(0);
                 let i = args.get_i64();
 
                 if precision as u64 > i32::MAX as u64 {
@@ -397,8 +404,8 @@ impl Spec {
                 precision,
                 alignment,
             } => {
-                let width = resolve_asterisk(*width, &mut args)?.unwrap_or(0);
-                let precision = resolve_asterisk(*precision, &mut args)?.unwrap_or(0);
+                let width = resolve_asterisk(*width, &mut args).unwrap_or(0);
+                let precision = resolve_asterisk(*precision, &mut args).unwrap_or(0);
                 let i = args.get_u64();
 
                 if precision as u64 > i32::MAX as u64 {
@@ -423,8 +430,8 @@ impl Spec {
                 alignment,
                 precision,
             } => {
-                let width = resolve_asterisk(*width, &mut args)?.unwrap_or(0);
-                let precision = resolve_asterisk(*precision, &mut args)?.unwrap_or(6);
+                let width = resolve_asterisk(*width, &mut args).unwrap_or(0);
+                let precision = resolve_asterisk(*precision, &mut args).unwrap_or(6);
                 let f = args.get_f64();
 
                 if precision as u64 > i32::MAX as u64 {
@@ -450,12 +457,30 @@ impl Spec {
 fn resolve_asterisk<'a>(
     option: Option<CanAsterisk<usize>>,
     mut args: impl ArgumentIter<'a>,
-) -> Result<Option<usize>, FormatError> {
-    Ok(match option {
+) -> Option<usize> {
+    match option {
         None => None,
         Some(CanAsterisk::Asterisk) => Some(usize::try_from(args.get_u64()).ok().unwrap_or(0)),
         Some(CanAsterisk::Fixed(w)) => Some(w),
-    })
+    }
+}
+
+fn resolve_asterisk_maybe_negative<'a>(
+    option: Option<CanAsterisk<usize>>,
+    mut args: impl ArgumentIter<'a>,
+) -> Option<(usize, bool)> {
+    match option {
+        None => None,
+        Some(CanAsterisk::Asterisk) => {
+            let nb = args.get_i64();
+            if nb < 0 {
+                Some((usize::try_from(-(nb as isize)).ok().unwrap_or(0), true))
+            } else {
+                Some((usize::try_from(nb).ok().unwrap_or(0), false))
+            }
+        }
+        Some(CanAsterisk::Fixed(w)) => Some((w, false)),
+    }
 }
 
 fn write_padded(

tests/by-util/test_printf.rs

@@ -495,6 +495,32 @@ fn sub_any_asterisk_hex_arg() {
         .stdout_only("0123456789");
 }
 
+#[test]
+fn sub_any_asterisk_negative_first_param() {
+    new_ucmd!()
+        .args(&["a(%*s)b", "-5", "xyz"])
+        .succeeds()
+        .stdout_only("a(xyz  )b"); // Would be 'a(  xyz)b' if -5 was 5
+
+    // Negative octal
+    new_ucmd!()
+        .args(&["a(%*s)b", "-010", "xyz"])
+        .succeeds()
+        .stdout_only("a(xyz     )b");
+
+    // Negative hexadecimal
+    new_ucmd!()
+        .args(&["a(%*s)b", "-0x10", "xyz"])
+        .succeeds()
+        .stdout_only("a(xyz             )b");
+
+    // Should also work on %c
+    new_ucmd!()
+        .args(&["a(%*c)b", "-5", "x"])
+        .succeeds()
+        .stdout_only("a(x    )b"); // Would be 'a(    x)b' if -5 was 5
+}
+
 #[test]
 fn sub_any_specifiers_no_params() {
     new_ucmd!()