Minor improvements to format field numbers

* src/editfns.c (styled_format): Allow field numbers in a %% spec.
No need for a special diagnostic for field numbers greater than
PTRDIFF_MAX.  Reword diagnostic for field 0.
* test/src/editfns-tests.el (format-with-field): Adjust to match.

1 files changed, 20 insertions, 36 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 44341cef2d3..98187df5d97 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -4046,9 +4046,8 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
              field-width ::= [0-9]+
              precision ::= '.' [0-9]*
 
-             If a field-number is specified, it specifies the argument
-             number to substitute.  Otherwise, the next argument is
-             taken.
+             If present, a field-number specifies the argument number
+             to substitute.  Otherwise, the next argument is taken.
 
              If a field-width is specified, it specifies to which width
              the output should be padded with blanks, if the output
@@ -4058,28 +4057,20 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
              digits to print after the '.' for floats, or the max.
              number of chars to print from a string.  */
 
-          char *field_end;
-          uintmax_t raw_field = strtoumax (format, &field_end, 10);
-          bool has_field = false;
-          if (c_isdigit (*format) && *field_end == '$')
-            {
-              if (raw_field < 1 || raw_field >= PTRDIFF_MAX)
-                {
-                  /* doprnt doesn't support %.*s, so we need to copy
-                     the field number string.  */
-                  ptrdiff_t length = field_end - format;
-                  eassert (length > 0);
-                  eassert (length < PTRDIFF_MAX);
-                  char *field = SAFE_ALLOCA (length + 1);
-                  memcpy (field, format, length);
-                  field[length] = '\0';
-                  error ("Invalid field number `%s'", field);
-                }
-              has_field = true;
-              /* n is incremented below.  */
-              n = raw_field - 1;
-              format = field_end + 1;
-            }
+          uintmax_t num;
+          char *num_end;
+          if (c_isdigit (*format))
+            {
+              num = strtoumax (format, &num_end, 10);
+              if (*num_end == '$')
+                {
+                  if (num == 0)
+                    error ("Invalid format field number 0");
+                  n = min (num, PTRDIFF_MAX);
+                  n--;
+                  format = num_end + 1;
+                }
+            }
 
           bool minus_flag = false;
           bool  plus_flag = false;
@@ -4104,11 +4095,10 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
           space_flag &= ! plus_flag;
           zero_flag &= ! minus_flag;
 
-          char *num_end;
-          uintmax_t raw_field_width = strtoumax (format, &num_end, 10);
-          if (max_bufsize <= raw_field_width)
+          num = strtoumax (format, &num_end, 10);
+          if (max_bufsize <= num)
             string_overflow ();
-          ptrdiff_t field_width = raw_field_width;
+          ptrdiff_t field_width = num;
 
           bool precision_given = *num_end == '.';
           uintmax_t precision = (precision_given
@@ -4123,13 +4113,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
           memset (&discarded[format0 - format_start], 1,
                   format - format0 - (conversion == '%'));
           if (conversion == '%')
-            {
-              if (has_field)
-                /* FIXME: `error' doesn't appear to support `%%'.  */
-                error ("Field number specified together with `%c' conversion",
-                       '%');
-              goto copy_char;
-            }
+            goto copy_char;
 
           ++n;
           if (! (n < nargs))