Fix mishandling of symbols that look like numbers

* src/bignum.c (make_neg_biguint): New function.
* src/lread.c (read1): Do not mishandle an unquoted symbol
with name equal to something like "1\0x", i.e., a string
of numeric form followed by a NUL byte.
Formerly these symbols were misread as numbers.
(string_to_number): Change last argument from an integer flag
to a pointer to the length.  This lets the caller figure out
how much of the prefix was used.  All callers changed.
Add a fast path if the integer (sans sign) fits in uintmax_t.
Update comments and simplify now that bignums are present.
* src/print.c (print_object): Fix quoting of symbols that look
like numbers, by relying on string_to_number for the tricky
cases rather than trying to redo its logic, incorrectly.  For
example, (read (prin1-to-string '\1e+NaN)) formerly returned
"1e+NaN", which was wrong: a backslash is needed in the output
to prevent it from being read as a NaN.  Escape NO_BREAK_SPACE
too, since lread.c treats it like SPACE.
* test/src/print-tests.el (print-read-roundtrip):
Add tests illustrating the abovementioned bugs.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/bignum.c b/src/bignum.c
index 0ab8de3ab7a..e3db0377a53 100644
--- a/src/bignum.c
+++ b/src/bignum.c
@@ -117,6 +117,16 @@ make_biguint (uintmax_t n)
   return make_bignum ();
 }
 
+/* Return a Lisp integer equal to -N, which must not be in fixnum range.  */
+Lisp_Object
+make_neg_biguint (uintmax_t n)
+{
+  eassert (-MOST_NEGATIVE_FIXNUM < n);
+  mpz_set_uintmax (mpz[0], n);
+  mpz_neg (mpz[0], mpz[0]);
+  return make_bignum ();
+}
+
 /* Return a Lisp integer with value taken from mpz[0].
    Set mpz[0] to a junk value.  */
 Lisp_Object