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, 6 insertions, 1 deletions

diff --git a/src/process.c b/src/process.c
index a9638dfc2df..6cda4f27acc 100644
--- a/src/process.c
+++ b/src/process.c
@@ -6852,7 +6852,12 @@ SIGCODE may be an integer, or a symbol whose name is a signal name.  */)
     {
       Lisp_Object tem = Fget_process (process);
       if (NILP (tem))
-        tem = string_to_number (SSDATA (process), 10, 0);
+        {
+          ptrdiff_t len;
+          tem = string_to_number (SSDATA (process), 10, &len);
+          if (NILP (tem) || len != SBYTES (process))
+            return Qnil;
+        }
       process = tem;
     }
   else if (!NUMBERP (process))