[patch, fortran] Add -fmax-errors option to limit the number of errors emitted.

[Brooks Moses <brooks dot moses at codesourcery dot com>]

PR 23538 mentions the utility of having an option that causes gfortran 
to give up and quit after emitting a certain number of errors.  The 
following patch implements this.

-----------------------------------------------------------------
2006-11-07  Brooks Moses  <brooks.moses@codesourcery.com>

	* lang.opt: Add -fmax-errors= option.
	* gfortran.h (gfc_option_t): Add max_errors element.
	* options.c (gfc_init_options): Set max_errors default value
	to 50.
	(gfc_handle_options): Check -fmax_errors value, assign to
	gfc_option.max_errors.
	* error.c (gfc_increment_error_count): New function, which
	also checks whether the error count exceeds max_errors.
	(gfc_warning): Use it.
	(gfc_notify_std): Use it.
	(gfc_warning_now): Use it.
	(gfc_error): Use it.
	(gfc_error_now): Use it.
	(gfc_error_check): Use it.
	(gfc_warning): Use it.
-----------------------------------------------------------------

Regtested on i686-pc-linux-gnu.  Ok for trunk?

(Once this is approved, I'll submit a corresponding documentation update.)

- Brooks
Index: lang.opt
===================================================================
--- lang.opt	(revision 118541)
+++ lang.opt	(working copy)
@@ -169,6 +169,10 @@
 Fortran RejectNegative Joined UInteger
 -ffree-line-length-<n>		Use n as character line width in free mode
 
+fmax-errors=
+Fortran RejectNegative Joined UInteger
+-fmax-errors=<n>	Maximum number of errors to report
+
 fmax-identifier-length=
 Fortran RejectNegative Joined UInteger
 -fmax-identifier-length=<n>	Maximum identifier length
Index: gfortran.h
===================================================================
--- gfortran.h	(revision 118541)
+++ gfortran.h	(working copy)
@@ -1629,6 +1629,7 @@
   int warn_surprising;
   int warn_tabs;
   int warn_underflow;
+  int max_errors;
 
   int flag_all_intrinsics;
   int flag_default_double;
Index: options.c
===================================================================
--- options.c	(revision 118541)
+++ options.c	(working copy)
@@ -61,6 +61,7 @@
   gfc_option.warn_surprising = 0;
   gfc_option.warn_tabs = 1;
   gfc_option.warn_underflow = 1;
+  gfc_option.max_errors = 50;
 
   gfc_option.flag_all_intrinsics = 0;
   gfc_option.flag_default_double = 0;
@@ -514,6 +515,12 @@
       gfc_option.flag_implicit_none = value;
       break;
 
+    case OPT_fmax_errors_:
+      if (value < 0)
+	gfc_fatal_error ("The -fmax_error value cannot be less than zero.");
+      gfc_option.max_errors = value;
+      break;
+
     case OPT_fmax_stack_var_size_:
       gfc_option.flag_max_stack_var_size = value;
       break;
Index: error.c
===================================================================
--- error.c	(revision 118541)
+++ error.c	(working copy)
@@ -460,6 +460,18 @@
 }
 
 
+/* Increment the number of errors, and check whether too many have 
+   been printed.  */
+
+static void
+gfc_increment_error_count (void)
+{
+  errors++;
+  if ((gfc_option.max_errors != 0) && (errors >= gfc_option.max_errors))
+    gfc_fatal_error ("Error count reached limit of %d.", gfc_option.max_errors);
+}
+
+
 /* Issue a warning.  */
 
 void
@@ -475,17 +487,17 @@
   cur_error_buffer = &warning_buffer;
 
   va_start (argp, nocmsgid);
+  error_print (_("Warning:"), _(nocmsgid), argp);
+  va_end (argp);
+
+  error_char ('\0');
+
   if (buffer_flag == 0)
   {
     warnings++;
     if (warnings_are_errors)
-      errors++;
+      gfc_increment_error_count();
   }
-
-  error_print (_("Warning:"), _(nocmsgid), argp);
-  va_end (argp);
-
-  error_char ('\0');
 }
 
 
@@ -530,13 +542,6 @@
   cur_error_buffer->flag = 1;
   cur_error_buffer->index = 0;
 
-  if (buffer_flag == 0)
-    {
-      if (warning && !warnings_are_errors)
-	warnings++;
-      else
-	errors++;
-    }
   va_start (argp, nocmsgid);
   if (warning)
     error_print (_("Warning:"), _(nocmsgid), argp);
@@ -545,6 +550,15 @@
   va_end (argp);
 
   error_char ('\0');
+
+  if (buffer_flag == 0)
+    {
+      if (warning && !warnings_are_errors)
+	warnings++;
+      else
+	gfc_increment_error_count();
+    }
+
   return (warning && !warnings_are_errors) ? SUCCESS : FAILURE;
 }
 
@@ -564,7 +578,7 @@
   buffer_flag = 0;
   warnings++;
   if (warnings_are_errors)
-    errors++;
+    gfc_increment_error_count();
 
   va_start (argp, nocmsgid);
   error_print (_("Warning:"), _(nocmsgid), argp);
@@ -615,12 +629,13 @@
   cur_error_buffer = &error_buffer;
 
   va_start (argp, nocmsgid);
-  if (buffer_flag == 0)
-    errors++;
   error_print (_("Error:"), _(nocmsgid), argp);
   va_end (argp);
 
   error_char ('\0');
+
+  if (buffer_flag == 0)
+    gfc_increment_error_count();
 }
 
 
@@ -638,13 +653,15 @@
 
   i = buffer_flag;
   buffer_flag = 0;
-  errors++;
 
   va_start (argp, nocmsgid);
   error_print (_("Error:"), _(nocmsgid), argp);
   va_end (argp);
 
   error_char ('\0');
+
+  gfc_increment_error_count();
+
   buffer_flag = i;
 
   if (flag_fatal_errors)
@@ -711,11 +728,12 @@
 
   if (error_buffer.flag)
     {
-      errors++;
       if (error_buffer.message != NULL)
 	fputs (error_buffer.message, stderr);
       error_buffer.flag = 0;
 
+      gfc_increment_error_count();
+
       if (flag_fatal_errors)
 	exit (1);
     }