bug#27779: 26.0.50: read -- Re-entering top level after C stack overflow

[npostavs]

Keith David Bershatsky <esq@lawlist.com> writes:

> By process of elimination via the lo-tech method of trying different
> nightly builds from https://emacsformacosx.com/builds/all , I have
> determined that December 8, 2016 was the last build where I am able to
> successfully run from the terminal:

Likely candidate: [1: f0a1e9ec3f], specifically the addition of stackbuf
in this hunk means read1 will use a lot more stack per call.

@@ -2541,8 +2556,9 @@ read_integer (Lisp_Object readcharfun, EMACS_INT radix)
 read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 {
   int c;
-  bool uninterned_symbol = 0;
+  bool uninterned_symbol = false;
   bool multibyte;
+  char stackbuf[MAX_ALLOCA];
 
   *pch = 0;

> At some point AFTER June 11, 2017, Emacs changed from
> crashing to just throwing an error message "Re-entering top level
> after C stack overflow".

I presume that's from [2: 9dee1c884e].

[1: f0a1e9ec3f]: 2016-12-08 13:00:32 -0800
  Make read1 more reentrant
  
http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=f0a1e9ec3fba3d5bea5bd62f525dba3fb005d1b1

[2: 9dee1c884e]: 2017-07-14 04:57:18 -0700
  Improve stack-overflow heuristic on GNU/Linux
  
http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=9dee1c884eb50ba282eb9dd2495c5269add25963