core: Initialize g_buf dynamically, add MES_STRING_MAX override.

* src/mes.c (g_buf, MAX_STRING): Move from strings.c.
(gc_init_cells): Initialize g_buf dynamically.
(main): Add environment override MES_MAX_STRING for MAX_STRING.
* doc/mes.texi (Environment Variables): Document it.

doc/mes.texi

@@ -757,6 +757,11 @@ The initial size of the arena @pxref{5.3,,, sicp, SICP} in cells.  Default: 20,0
 
 The maximum size of the arena in cells.  Default: 100,000,000.
 
+@item MES_MAX_STRING
+@vindex MES_MAX_STRING
+
+The maximum size of a string.  Default: 524,288.
+
 @item MES_DEBUG
 @vindex MES_DEBUG
 

src/mes.c

@@ -38,12 +38,16 @@ long STACK_SIZE = 20000;
 long JAM_SIZE = 20000;
 long GC_SAFETY = 2000;
 
+long MAX_STRING = 524288;
+
 char *g_arena = 0;
 typedef long SCM;
 
 int g_debug = 0;
 long g_free = 0;
 
+char *g_buf = 0;
+
 SCM g_continuations = 0;
 SCM g_symbols = 0;
 SCM g_stack = 0;
@@ -1647,6 +1651,10 @@ gc_init_cells () ///((internal))
   g_cells++;
   TYPE (0) = TCHAR;
   VALUE (0) = 'c';
+
+  // FIXME: remove MES_MAX_STRING, grow dynamically
+  g_buf = (char*)malloc (MAX_STRING);
+
   return 0;
 }
 
@@ -2276,6 +2284,8 @@ main (int argc, char *argv[])
     GC_SAFETY = atoi (p);
   if (p = getenv ("MES_STACK"))
     STACK_SIZE = atoi (p);
+  if (p = getenv ("MES_MAX_STRING"))
+    MAX_STRING = atoi (p);
   g_stdin = STDIN;
   g_stdout = STDOUT;
   g_stderr = STDERR;

src/strings.c

@@ -18,13 +18,10 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#define MAX_STRING 524288
-char g_buf[MAX_STRING];
-
 void
 assert_max_string (size_t i, char const* msg, char* string)
 {
-  if (i > MAX_STRING) // Mes must be able to make g_buf
+  if (i > MAX_STRING)
     {
       eputs (msg);
       eputs (":string too long[");