[Fortran] Truncate warn with OpenMP/OpenACC/!GCC$ (PR94709)

While '!$' with -fopenmp unsets too often load_line's seen_comment flag,
this only affects <tab> warnings; for trunction warnings, gfc_next_char_literal
re-handles the directives correctly.  In terms of missed warnings, a directive
that is completely in the truncated part is not diagnosted (as it starts
with a '!').

        PR fortran/94709
        * scanner.c (load_line): In fixed form, also treat 'C' as comment and
        'D'/'d' only with -fd-lines-as-comments. Treat '!$' with -fopenmp,
        '!$acc' with -fopenacc and '!GCC$' as non-comment to permit <tab>
        and truncation warnings.

        PR fortran/94709
        * gfortran.dg/gomp/warn_truncated.f: New.
        * gfortran.dg/gomp/warn_truncated.f90: New.

5 files changed, 94 insertions, 11 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 9eadcdb..e02815e 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,11 @@
+2020-04-22  Tobias Burnus  <tobias@codesourcery.com>
+
+	PR fortran/94709
+	* scanner.c (load_line): In fixed form, also treat 'C' as comment and
+	'D'/'d' only with -fd-lines-as-comments. Treat '!$' with -fopenmp,
+	'!$acc' with -fopenacc and '!GCC$' as non-comment to permit <tab>
+	and truncation warnings.
+
 2020-04-20  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	* dump-parse-tree.c (show_attr): Add numerous flags, some cleanup.
diff --git a/gcc/fortran/scanner.c b/gcc/fortran/scanner.c
index f65594f..6f93508 100644
--- a/gcc/fortran/scanner.c
+++ b/gcc/fortran/scanner.c
@@ -1755,11 +1755,15 @@ static int
 load_line (FILE *input, gfc_char_t **pbuf, int *pbuflen, const int *first_char)
 {
   int c, maxlen, i, preprocessor_flag, buflen = *pbuflen;
-  int trunc_flag = 0, seen_comment = 0;
-  int seen_printable = 0, seen_ampersand = 0, quoted = ' ';
-  gfc_char_t *buffer;
+  int quoted = ' ', comment_ix = -1;
+  bool seen_comment = false;
+  bool first_comment = true;
+  bool trunc_flag = false;
+  bool seen_printable = false;
+  bool seen_ampersand = false;
   bool found_tab = false;
   bool warned_tabs = false;
+  gfc_char_t *buffer;
 
   /* Determine the maximum allowed line length.  */
   if (gfc_current_form == FORM_FREE)
@@ -1794,7 +1798,7 @@ load_line (FILE *input, gfc_char_t **pbuf, int *pbuflen, const int *first_char)
 
   /* In order to not truncate preprocessor lines, we have to
      remember that this is one.  */
-  preprocessor_flag = (c == '#' ? 1 : 0);
+  preprocessor_flag = (c == '#');
 
   for (;;)
     {
@@ -1824,20 +1828,24 @@ load_line (FILE *input, gfc_char_t **pbuf, int *pbuflen, const int *first_char)
 	{
 	  if (seen_ampersand)
 	    {
-	      seen_ampersand = 0;
-	      seen_printable = 1;
+	      seen_ampersand = false;
+	      seen_printable = true;
 	    }
 	  else
-	    seen_ampersand = 1;
+	    seen_ampersand = true;
 	}
 
       if ((c != '&' && c != '!' && c != ' ') || (c == '!' && !seen_ampersand))
-	seen_printable = 1;
+	seen_printable = true;
 
       /* Is this a fixed-form comment?  */
       if (gfc_current_form == FORM_FIXED && i == 0
-	  && (c == '*' || c == 'c' || c == 'd'))
-	seen_comment = 1;
+	  && (c == '*' || c == 'c' || c == 'C'
+	      || (gfc_option.flag_d_lines != -1 && (c == 'd' || c == 'D'))))
+	{
+	  seen_comment = true;
+	  comment_ix = i;
+	}
 
       if (quoted == ' ')
 	{
@@ -1849,7 +1857,34 @@ load_line (FILE *input, gfc_char_t **pbuf, int *pbuflen, const int *first_char)
 
       /* Is this a free-form comment?  */
       if (c == '!' && quoted == ' ')
-        seen_comment = 1;
+	{
+	  if (seen_comment)
+	    first_comment = false;
+	  seen_comment = true;
+	  comment_ix = i;
+	}
+
+      /* For truncation and tab warnings, set seen_comment to false if one has
+	 either an OpenMP or OpenACC directive - or a !GCC$ attribute.  If
+	 OpenMP is enabled, use '!$' as as conditional compilation sentinel
+	 and OpenMP directive ('!$omp').  */
+      if (seen_comment && first_comment && flag_openmp && comment_ix + 1 == i
+	  && c == '$')
+	first_comment = seen_comment = false;
+      if (seen_comment && first_comment && comment_ix + 4 == i)
+	{
+	  if (((*pbuf)[comment_ix+1] == 'g' || (*pbuf)[comment_ix+1] == 'G')
+	      && ((*pbuf)[comment_ix+2] == 'c' || (*pbuf)[comment_ix+2] == 'C')
+	      && ((*pbuf)[comment_ix+3] == 'c' || (*pbuf)[comment_ix+3] == 'C')
+	      && (*pbuf)[comment_ix+4] == '$')
+	    first_comment = seen_comment = false;
+	  if (flag_openacc
+	      && (*pbuf)[comment_ix+1] == '$'
+	      && ((*pbuf)[comment_ix+2] == 'a' || (*pbuf)[comment_ix+2] == 'A')
+	      && ((*pbuf)[comment_ix+3] == 'c' || (*pbuf)[comment_ix+3] == 'C')
+	      && ((*pbuf)[comment_ix+4] == 'c' || (*pbuf)[comment_ix+4] == 'C'))
+	    first_comment = seen_comment = false;
+	}
 
       /* Vendor extension: "<tab>1" marks a continuation line.  */
       if (found_tab)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7ba2c72..36b2893 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-22  Tobias Burnus  <tobias@codesourcery.com>
+
+	PR fortran/94709
+	* gfortran.dg/gomp/warn_truncated.f: New.
+	* gfortran.dg/gomp/warn_truncated.f90: New.
+
 2020-04-22  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR tree-optimization/94700
diff --git a/gcc/testsuite/gfortran.dg/gomp/warn_truncated.f b/gcc/testsuite/gfortran.dg/gomp/warn_truncated.f
new file mode 100644
index 0000000..5b50b8a
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/warn_truncated.f
@@ -0,0 +1,15 @@
+! { dg-do compile }
+! { dg-additional-options "-Wall" }
+!
+! PR fortran/94709
+!
+! Check that 'Line truncated' gets printed as appropriate
+!
+c$omp target                                                            ! map()
+c$omp end target
+
+c$omp target                                                            map() ! { dg-warning "Line truncated" }
+c$acc declare                                                           map()
+ca =                                                                    5
+c$omp end target
+       end
diff --git a/gcc/testsuite/gfortran.dg/gomp/warn_truncated.f90 b/gcc/testsuite/gfortran.dg/gomp/warn_truncated.f90
new file mode 100644
index 0000000..86d7eb2
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/warn_truncated.f90
@@ -0,0 +1,19 @@
+! { dg-do compile }
+!
+! PR fortran/94709
+!
+! Check that 'Line truncated' gets printed as appropriate
+!
+integer i
+i = 0
+!$omp target                                                                                                                                        ! map()
+!$omp end target
+
+!$omp target                                                                                                                                        map() ! { dg-error "Line truncated" }
+!$acc kernels                                                                                                                                       copy()
+!a =                                                                                                                                                 5
+!$acc end kernels
+!$omp end target
+end
+
+! { dg-message "some warnings being treated as errors" "" {target "*-*-*"} 0 }