Add sv_string7 and sv_stting7b tests.

These test string assignments of various escaped special characters.

ivtest/ivltests/sv_string7.v

@@ -0,0 +1,45 @@
+
+module main;
+
+   string foo;
+   int 	  error_count;
+
+   task check_char(input int idx, input [7:0] val);
+      if (foo[idx] !== val) begin
+	 $display("FAILED: foo[%0d]==%02h, expecting %02h",
+		  idx, foo[idx], val);
+	 error_count = error_count+1;
+      end
+   endtask // check_char
+   
+   initial begin
+      // These are the special charasters in strings as defined by
+      // IEEE Std 1800-2017: 5.9.1 Special characters in strings.
+      // The string assignment is governed by:
+      // IEEE Std 1800-2017: 6.16 String data type
+      foo = "abc\n\t\\\"\v\f\a\001\002\x03\x04";
+      error_count = 0;
+
+      check_char(0, 8'h61); // 'a'
+      check_char(1, 8'h62); // 'b'
+      check_char(2, 8'h63); // 'c'
+      check_char(3, 8'h0a); // '\n'
+      check_char(4, 8'h09); // '\t'
+      check_char(5, 8'h5c); // '\\'
+      check_char(6, 8'h22); // '\"'
+      check_char(7, 8'h0b); // '\v'
+      check_char(8, 8'h0c); // '\f'
+      check_char(9, 8'h07); // '\a'
+      check_char(10, 8'h01); // '\001'
+      check_char(11, 8'h02); // '\002'
+      check_char(12, 8'h03); // '\x03'
+      check_char(13, 8'h04); // '\x04'
+
+      if (foo.len() !== 14) begin
+	 $display("FAILED: foo.len() == %0d, should be 14", foo.len());
+	 error_count = error_count+1;
+      end
+
+      if (error_count == 0) $display("PASSED");
+   end
+endmodule // main

ivtest/ivltests/sv_string7b.v

@@ -0,0 +1,46 @@
+
+module main;
+
+   string foo;
+   int 	  error_count;
+
+   task check_char(input int idx, input [7:0] val);
+      if (foo[idx] !== val) begin
+	 $display("FAILED: foo[%0d]==%02h, expecting %02h",
+		  idx, foo[idx], val);
+	 error_count = error_count+1;
+      end
+   endtask // check_char
+   
+   initial begin
+      // These are the special charasters in strings as defined by
+      // IEEE Std 1800-2017: 5.9.1 Special characters in strings.
+      // The string assignment is governed by:
+      // IEEE Std 1800-2017: 6.16 String data type
+      foo = "abc";
+      foo = {foo, "\n\t\\\"\v\f\a\001\002\x03\x04"};
+      error_count = 0;
+
+      check_char(0, 8'h61); // 'a'
+      check_char(1, 8'h62); // 'b'
+      check_char(2, 8'h63); // 'c'
+      check_char(3, 8'h0a); // '\n'
+      check_char(4, 8'h09); // '\t'
+      check_char(5, 8'h5c); // '\\'
+      check_char(6, 8'h22); // '\"'
+      check_char(7, 8'h0b); // '\v'
+      check_char(8, 8'h0c); // '\f'
+      check_char(9, 8'h07); // '\a'
+      check_char(10, 8'h01); // '\001'
+      check_char(11, 8'h02); // '\002'
+      check_char(12, 8'h03); // '\x03'
+      check_char(13, 8'h04); // '\x04'
+
+      if (foo.len() !== 14) begin
+	 $display("FAILED: foo.len() == %0d, should be 14", foo.len());
+	 error_count = error_count+1;
+      end
+
+      if (error_count == 0) $display("PASSED");
+   end
+endmodule // main

ivtest/regress-sv.list

@@ -530,6 +530,8 @@ sv_string3		normal,-g2009		ivltests
 sv_string4		normal,-g2009		ivltests
 sv_string5		normal,-g2009		ivltests
 sv_string6		normal,-g2009		ivltests
+sv_string7		normal,-g2009		ivltests
+sv_string7b		normal,-g2009		ivltests
 sv_timeunit_prec1	normal,-g2005-sv	ivltests
 sv_timeunit_prec2	normal,-g2009		ivltests
 sv_timeunit_prec3a	normal,-g2005-sv	ivltests gold=sv_timeunit_prec3a.gold