[Bug fortran/58001] Make it possible to silence "Extension: Tab character in format" warning

[sgk at troutmask dot apl.washington.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58001

--- Comment #9 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
The following patch causes gfortran to treat a tab within
a FORMAT statement that same as it does elsewhere for the
appearance of a nonconforming use of tab.  The two tet
cases have been adjusted.

Index: gcc/fortran/io.c
===================================================================
--- gcc/fortran/io.c    (revision 201382)
+++ gcc/fortran/io.c    (working copy)
@@ -192,23 +192,14 @@ unget_char (void)
 /* Eat up the spaces and return a character.  */

 static char
-next_char_not_space (bool *error)
+next_char_not_space ()
 {
   char c;
   do
     {
       error_element = c = next_char (NONSTRING);
-      if (c == '\t')
-    {
-      if (gfc_option.allow_std & GFC_STD_GNU)
-        gfc_warning ("Extension: Tab character in format at %C");
-      else
-        {
-          gfc_error ("Extension: Tab character in format at %C");
-          *error = true;
-          return c;
-        }
-    }
+      if (!gfc_option.warn_tabs && c == '\t')
+      gfc_warning ("Nonconforming tab character in FORMAT at %C");
     }
   while (gfc_is_whitespace (c));
   return c;
@@ -226,7 +217,6 @@ format_lex (void)
   char c, delim;
   int zflag;
   int negative_flag;
-  bool error = false;

   if (saved_token != FMT_NONE)
     {
@@ -235,7 +225,7 @@ format_lex (void)
       return token;
     }

-  c = next_char_not_space (&error);
+  c = next_char_not_space ();

   negative_flag = 0;
   switch (c)
@@ -245,7 +235,7 @@ format_lex (void)
       /* Falls through.  */

     case '+':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (!ISDIGIT (c))
     {
       token = FMT_UNKNOWN;
@@ -256,7 +246,7 @@ format_lex (void)

       do
     {
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (ISDIGIT (c))
         value = 10 * value + c - '0';
     }
@@ -286,7 +276,7 @@ format_lex (void)

       do
     {
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (ISDIGIT (c))
         {
           value = 10 * value + c - '0';
@@ -321,7 +311,7 @@ format_lex (void)
       break;

     case 'T':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       switch (c)
     {
     case 'L':
@@ -349,7 +339,7 @@ format_lex (void)
       break;

     case 'S':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (c != 'P' && c != 'S')
     unget_char ();

@@ -357,7 +347,7 @@ format_lex (void)
       break;

     case 'B':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (c == 'N' || c == 'Z')
     token = FMT_BLANK;
       else
@@ -419,7 +409,7 @@ format_lex (void)
       break;

     case 'E':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (c == 'N' )
     token = FMT_EN;
       else if (c == 'S')
@@ -449,7 +439,7 @@ format_lex (void)
       break;

     case 'D':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       if (c == 'P')
     {
       if (!gfc_notify_std (GFC_STD_F2003, "DP format "
@@ -472,7 +462,7 @@ format_lex (void)
       break;

     case 'R':
-      c = next_char_not_space (&error);
+      c = next_char_not_space ();
       switch (c)
     {
     case 'C':
@@ -513,9 +503,6 @@ format_lex (void)
       break;
     }

-  if (error)
-    return FMT_ERROR;
-
   return token;
 }

Index: gcc/testsuite/gfortran.dg/fmt_tab_1.f90
===================================================================
--- gcc/testsuite/gfortran.dg/fmt_tab_1.f90    (revision 201382)
+++ gcc/testsuite/gfortran.dg/fmt_tab_1.f90    (working copy)
@@ -1,6 +1,9 @@
-! { dg-do run }
+! { dg-do compile }
+! { dg-options "-Wtabs" }
 ! PR fortran/32987
       program TestFormat
         write (*, 10)
- 10     format ('Hello ',    'bug!') ! { dg-warning "Extension: Tab character
in format" }
+        ! There is a tab character before 'bug'.  This is accepted without
+        ! the -Wno-tabs option or a -std= option.
+ 10     format ('Hello ',    'bug!')
       end
Index: gcc/testsuite/gfortran.dg/fmt_tab_2.f90
===================================================================
--- gcc/testsuite/gfortran.dg/fmt_tab_2.f90    (revision 201382)
+++ gcc/testsuite/gfortran.dg/fmt_tab_2.f90    (working copy)
@@ -2,6 +2,6 @@
 ! { dg-options "-std=f2003" }
 ! PR fortran/32987
       program TestFormat
-        write (*, 10) ! { dg-error "FORMAT label 10 at .1. not defined" }
- 10     format ('Hello ',    'bug!') ! { dg-error "Extension: Tab character in
format" }
+        write (*, 10)
+ 10     format ('Hello ',    'bug!') ! { dg-warning "tab character in FORMAT"
}
       end