Fix edge cases in snprintf

rust-embedded-community · Oct 25, 2024 · d7349e4 · d7349e4
1 parent dd6f569
commit d7349e4
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Showing 2 changed files with 36 additions and 7 deletions.
diff --git a/src/snprintf.c b/src/snprintf.c
@@ -210,6 +210,7 @@ int vsnprintf(
             {
                char s[MAXIMUM_NUMBER_LENGTH] = { 0 };
                signed long long ll = 0;
+               unsigned long long ull = 0;
                if ( is_long == 2 )
                {
                   // Render %lld
@@ -226,11 +227,8 @@ int vsnprintf(
                   ll = va_arg( ap, signed int );
                }
                bool is_negative = ll < 0;
-               if (is_negative)
-               {
-                  ll = -ll;
-               }
-               itoa( ll, s, sizeof(s), 10 );
+               ull = is_negative ? -ll : ll;
+               utoa( ull, s, sizeof(s), 10 );
                write_padding( str, size, &written, strlen(s), width, precision, zero_pad, is_negative );
                for ( const char* p = s; *p != '\0'; p++ )
                {
@@ -430,10 +428,13 @@ static void write_padding(char* restrict str, size_t size, size_t* written, size
    unsigned long zero_pad_len = 0;
    if ( precision != 0 && precision != (unsigned long)-1 )
    {
-      zero_pad_len = precision > len ? precision - len : 0;
       if ( is_negative )
       {
-         zero_pad_len++;
+         zero_pad_len = precision >= len ? precision - len + 1 : 0;
+      }
+      else
+      {
+         zero_pad_len = precision >= len ? precision - len : 0;
       }
    }
    else if ( zero_pad )

diff --git a/src/snprintf.rs b/src/snprintf.rs
@@ -94,6 +94,34 @@ mod test {
 		);
 	}
 
+	#[test]
+	fn int_min() {
+		asprintf(
+			"%d",
+			&format!("{}", CInt::min_value()),
+			|buf, len, fmt| unsafe { snprintf(buf, len, fmt, CInt::min_value()) },
+		);
+		asprintf(
+			"%lld",
+			&format!("{}", CLongLong::min_value()),
+			|buf, len, fmt| unsafe { snprintf(buf, len, fmt, CLongLong::min_value()) },
+		);
+	}
+
+	#[test]
+	fn int_max() {
+		asprintf(
+			"%d",
+			&format!("{}", CInt::max_value()),
+			|buf, len, fmt| unsafe { snprintf(buf, len, fmt, CInt::max_value()) },
+		);
+		asprintf(
+			"%lld",
+			&format!("{}", CLongLong::max_value()),
+			|buf, len, fmt| unsafe { snprintf(buf, len, fmt, CLongLong::max_value()) },
+		);
+	}
+
 	#[test]
 	fn non_null_terminated_with_length() {
 		asprintf("%.*s", "01234", |buf, len, fmt: *const u8| unsafe {