[patch, libgfortran] PR114304 - [13/14 Regression] libgfortran I/O – bogus "Semicolon not allowed as separator with DECIMAL='point'"

[Jerry D <jvdelisle2@gmail.com>]

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Hi all,

The attached log entry and patch (git show) fixes this issue by adding 
logic to handle spaces in eat_separators. One or more spaces by 
themselves are a valid separator. So in this case we look at the 
character following the spaces to see if it is a comma or semicolon.

If so, I change it to the valid separator for the given decimal mode, 
point or comma. This allows the comma or semicolon to be interpreted as 
a null read on the next effective item in the formatted read.

I chose a permissive approach here that allows reads to proceed when the
input line is mal-formed with an incorrect separator as long as there is 
at least one space in front of it.

New test case included. Regression tested on X86-64.

OK for trunk?  Backport to 13 after some time.

Regards,

Jerry

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commit 7d1a958d6b099ea88b6c51649baf5dbd5e598909
Author: Jerry DeLisle <jvdelisle@gcc.gnu.org>
Date:   Wed Apr 3 18:07:30 2024 -0700

    libfortran: Fix handling of formatted separators.
    
            PR libfortran/114304
    
    libgfortran/ChangeLog:
    
            * io/list_read.c (eat_separator): Add logic to handle spaces
            preceding a comma or semicolon such that that a 'null' read
            occurs without error at the end of comma or semicolon
            terminated input lines.
    
    gcc/testsuite/ChangeLog:
    
            * gfortran.dg/pr114304.f90: New test.

diff --git a/gcc/testsuite/gfortran.dg/pr114304.f90 b/gcc/testsuite/gfortran.dg/pr114304.f90
new file mode 100644
index 00000000000..57af619246b
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr114304.f90
@@ -0,0 +1,49 @@
+! { dg-do run }
+! pr114304
+real :: x(3)
+character(len=1) :: s
+integer :: ios
+
+s = 'x'
+
+open(99, decimal="comma", status='scratch')
+write(99, '(a)') '1,23435 1243,24 13,24 a'
+rewind(99)
+read(99, *, iostat=ios) x, s
+if (ios /= 0 .or. s /= 'a') stop 1
+
+rewind(99)
+write(99, '(a)') '1,23435;1243,24;13,24;a'
+rewind(99)
+read(99, *, iostat=ios) x, s
+if (ios /= 0 .or. s /= 'a') stop 2
+
+! Note: not reading 's'
+rewind(99)
+write(99, '(a)') '1,23435 1243,24 13,24 ,'
+rewind(99)
+read(99, *) x
+if (ios /= 0) stop 3
+
+rewind(99)
+write(99, '(a)') '1,23435;1243,24;13,24 ,'
+rewind(99)
+read(99, *, iostat=ios) x
+if (ios /= 0) stop 4
+
+! Now reading 's'
+s = 'w'
+rewind(99)
+write(99, '(a)') '1,23435 1243,24 13,24 ,'
+rewind(99)
+read(99, *, iostat=ios) x, s
+if (ios /= 0 .or. s /= 'w') stop 5
+
+s = 'w'
+rewind(99)
+write(99, '(a)') '1,23435;1243,24;13,24 ,'
+rewind(99)
+read(99, *, iostat=ios) x, s
+if (ios /= 0 .or. s /= 'w') stop 6
+close(99)
+end
diff --git a/libgfortran/io/list_read.c b/libgfortran/io/list_read.c
index fb3f7dbc34d..f6f169043bf 100644
--- a/libgfortran/io/list_read.c
+++ b/libgfortran/io/list_read.c
@@ -461,11 +461,30 @@ eat_separator (st_parameter_dt *dtp)
   int c, n;
   int err = 0;
 
-  eat_spaces (dtp);
   dtp->u.p.comma_flag = 0;
+  c = next_char (dtp);
+  if (c == ' ')
+    {
+      eat_spaces (dtp);
+      c = next_char (dtp);
+      if (c == ',')
+	{
+	  if (dtp->u.p.current_unit->decimal_status == DECIMAL_COMMA)
+	    unget_char (dtp, ';');
+	  dtp->u.p.comma_flag = 1;
+	  eat_spaces (dtp);
+	  return err;
+	}
+      if (c == ';')
+	{
+	  if (dtp->u.p.current_unit->decimal_status == DECIMAL_POINT)
+	    unget_char (dtp, ',');
+	  dtp->u.p.comma_flag = 1;
+	  eat_spaces (dtp);
+	  return err;
+	}
+    }
 
-  if ((c = next_char (dtp)) == EOF)
-    return LIBERROR_END;
   switch (c)
     {
     case ',':
@@ -476,7 +495,10 @@ eat_separator (st_parameter_dt *dtp)
 	  unget_char (dtp, c);
 	  break;
 	}
-    /* Fall through. */
+      dtp->u.p.comma_flag = 1;
+      eat_spaces (dtp);
+      break;
+
     case ';':
       dtp->u.p.comma_flag = 1;
       eat_spaces (dtp);