Make octal/hex escapes in printf and echo output literal bytes

Fixes #1894

builtin.cpp

@@ -1937,8 +1937,8 @@ static int builtin_echo(parser_t &parser, wchar_t **argv)
                         unsigned char narrow_val = 0;
                         if (builtin_echo_parse_numeric_sequence(str + j + 1, &consumed, &narrow_val))
                         {
-                            /* Here consumed must have been set to something */
+                            /* Here consumed must have been set to something. The narrow_val is a literal byte that we want to output (#1894) */
-                            wc = narrow_val; //is this OK for conversion?
+                            wc = ENCODE_DIRECT_BASE + narrow_val % 256;
                         }
                         else
                         {

builtin_printf.cpp

@@ -357,16 +357,17 @@ long builtin_printf_state_t::print_esc(const wchar_t *escstart, bool octal_0)
             esc_value = esc_value * 16 + hex_to_bin(*p);
         if (esc_length == 0)
             this->fatal_error(_(L"missing hexadecimal number in escape"));
-        this->append_output(esc_value);
+        this->append_output(ENCODE_DIRECT_BASE + esc_value % 256);
     }
     else if (is_octal_digit(*p))
     {
         /* Parse \0ooo (if octal_0 && *p == L'0') or \ooo (otherwise).
         Allow \ooo if octal_0 && *p != L'0'; this is an undocumented
         extension to POSIX that is compatible with Bash 2.05b.  */
+        /* Wrap mod 256, which matches historic behavior */
         for (esc_length = 0, p += octal_0 && *p == L'0'; esc_length < 3 && is_octal_digit(*p); ++esc_length, ++p)
             esc_value = esc_value * 8 + octal_to_bin(*p);
-        this->append_output(esc_value);
+        this->append_output(ENCODE_DIRECT_BASE + esc_value % 256);
     }
     else if (*p && wcschr(L"\"\\abcefnrtv", *p))
     {

tests/printf.in

@@ -30,4 +30,8 @@ echo
 # Bogus printf specifier, should produce no stdout
 printf "%5" 10 ^ /dev/null
 
+# Octal escapes produce literal bytes, not characters
+# \376 is 0xFE
+printf '\376' | xxd -p
+
 true

tests/printf.out

@@ -13,3 +13,4 @@ foobarbaz
 I P Q R
 Test escapes
 a
+fe

tests/test1.in

@@ -118,6 +118,8 @@ echo -e 'abc\cdef' # won't output a newline!
 echo ''
 echo -
 
+echo -ne '\376' | xxd -p
+
 echo -e Catch your breath
 
 echo -e 'abc\x21def'

tests/test1.out

@@ -34,6 +34,7 @@ abcQdef
 abcQ2def
 abc
 -
+fe
 Catch your breath
 abc!def
 abc!1def