PR 81552 Improve and document -flag-init-integer

Make the option handling code parse the -flag-init-integer value as a
C long type, allowing a larger range on systems where long is a larger
type than int.  Document the behavior.

Regtested on x86_64-pc-linux-gnu, committed as obvious.

2019-02-14  Janne Blomqvist  <jb@gcc.gnu.org>

        PR fortran/81552
        * gfortran.h (gfc_option_t): Make flag_init_integer_value a long.
        * options.c (gfc_handle_option): Use strtol instead of atoi.
        * invoke.texi: Document -finit-integer behavior in more detail

From-SVN: r268906

gcc/fortran/ChangeLog

+2019-02-14  Janne Blomqvist  <jb@gcc.gnu.org>
+
+	PR fortran/81552
+	* gfortran.h (gfc_option_t): Make flag_init_integer_value a long.
+	* options.c (gfc_handle_option): Use strtol instead of atoi.
+	* invoke.texi: Document -finit-integer behavior in more detail.
+
 2019-02-14  Harald Anlauf  <anlauf@gmx.de>
 
 	PR fortran/88248

gcc/fortran/gfortran.h

@@ -2681,7 +2681,7 @@ typedef struct
   int flag_preprocessed;
   int flag_d_lines;
   int flag_init_integer;
-  int flag_init_integer_value;
+  long flag_init_integer_value;
   int flag_init_logical;
   int flag_init_character;
   char flag_init_character_value;

gcc/fortran/invoke.texi

@@ -1779,6 +1779,11 @@ use @option{-finit-real=snan}; note, however, that compile-time
 optimizations may convert them into quiet NaN and that trapping
 needs to be enabled (e.g. via @option{-ffpe-trap}).
 
+The @option{-finit-integer} option will parse the value into an
+integer of type @code{INTEGER(kind=C_LONG)} on the host.  Said value
+is then assigned to the integer variables in the Fortran code, which
+might result in wraparound if the value is too large for the kind.
+
 Finally, note that enabling any of the @option{-finit-*} options will
 silence warnings that would have been emitted by @option{-Wuninitialized}
 for the affected local variables.

gcc/fortran/options.c

@@ -708,7 +708,7 @@ gfc_handle_option (size_t scode, const char *arg, HOST_WIDE_INT value,
 
     case OPT_finit_integer_:
       gfc_option.flag_init_integer = GFC_INIT_INTEGER_ON;
-      gfc_option.flag_init_integer_value = atoi (arg);
+      gfc_option.flag_init_integer_value = strtol (arg, NULL, 10);
       break;
 
     case OPT_finit_character_: