Add regression tests for string formatting of null-bytes through VPI

Check that null-bytes get removed when reading a value through the VPI API
as a vpiStringVal. Also check that null-bytes are not removed from string
literals when string literals are read through the VPI API as a non
vpiStringVal.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

ivtest/gold/br_gh827.gold

@@ -0,0 +1,4 @@
+Const Positive yes
+Const Negative  NO
+Var Positive yes
+Var Negative  NO

ivtest/ivltests/br_gh827.v

@@ -0,0 +1,9 @@
+module test;
+   reg expected = 1;
+   initial begin
+      $display("Const Positive %s", 1 ? "yes" : "NO");
+      $display("Const Negative %s", !1 ? "yes" : "NO");
+      $display("Var Positive %s", expected ? "yes" : "NO");
+      $display("Var Negative %s", !expected ? "yes" : "NO");
+   end
+endmodule

ivtest/ivltests/string13.v

@@ -0,0 +1,58 @@
+// Check that null-bytes are handled consistently between string literals,
+// number literals and signals of all kinds, especially when formatting as a
+// string.
+
+module test;
+
+  reg failed = 1'b0;
+
+  `define check(val, exp) \
+    if (val != exp) begin \
+      $display("FAILED(%0d): Expected '%0s', got '%0s'.", `__LINE__, exp, val); \
+      failed = 1'b1; \
+    end
+
+  reg [255:0] s;
+  reg [31:0] x;
+  reg [31:0] y[1:0];
+  wire [31:0] z;
+  wire [31:0] w;
+
+  assign z = "\000a\000b";
+  assign w = 32'h00610062;
+
+  initial begin
+    $sformat(s, ":%x:%0x:%s:%0s:", "\000a\000b", "\000a\000b", "\000a\000b", "\000a\000b");
+    `check(s, ":00610062:610062: a b:a b:")
+    $sformat(s, ":%x:%0x:%s:%0s:", 32'h00610062, 32'h00610062, 32'h00610062, 32'h00610062);
+    `check(s, ":00610062:610062: a b:a b:")
+
+    x = "\000a\000b";
+    $sformat(s, ":%x:%0x:%s:%0s:", x, x, x, x);
+    `check(s, ":00610062:610062: a b:a b:")
+
+    x = 32'h00610062;
+    $sformat(s, ":%x:%0x:%s:%0s:", x, x, x, x);
+    `check(s, ":00610062:610062: a b:a b:")
+
+    y[0] = "\000a\000b";
+    $sformat(s, ":%x:%0x:%s:%0s:", y[0], y[0], y[0], y[0]);
+    `check(s, ":00610062:610062: a b:a b:")
+
+    y[1] = 32'h00610062;
+    $sformat(s, ":%x:%0x:%s:%0s:", y[1], y[1], y[1], y[1]);
+    `check(s, ":00610062:610062: a b:a b:")
+
+    $sformat(s, ":%x:%0x:%s:%0s:", z, z, z, z);
+    `check(s, ":00610062:610062: a b:a b:")
+
+    $sformat(s, ":%x:%0x:%s:%0s:", w, w, w, w);
+    `check(s, ":00610062:610062: a b:a b:")
+
+
+    if (!failed) begin
+      $display("PASSED");
+    end
+  end
+
+endmodule

ivtest/ivltests/string14.v

@@ -0,0 +1,38 @@
+// Check that the empty string "" is equivalent to 8'h00
+
+module test;
+
+  reg failed = 1'b0;
+
+  `define check(val, exp) \
+    if (val != exp) begin \
+      $display("FAILED(%0d): Expected '%0s', got '%0s'.", `__LINE__, exp, val); \
+      failed = 1'b1; \
+    end
+
+  reg [47:0] s;
+  reg [7:0] x;
+  wire [7:0] y;
+
+  assign y = "";
+
+  initial begin
+    `check("", 8'h00);
+    `check($bits(""), 8);
+
+    $sformat(s, ":%s:%0s:", "", "");
+    `check(s, ": ::");
+
+    x = 8'h00;
+    $sformat(s, ":%s:%0s:", x, x);
+    `check(s, ": ::");
+
+    $sformat(s, ":%s:%0s:", y, y);
+    `check(s, ": ::");
+
+    if (!failed) begin
+      $display("PASSED");
+    end
+  end
+
+endmodule

ivtest/regress-vlg.list

@@ -355,6 +355,7 @@ br_gh782e		normal			ivltests
 br_gh782f		normal			ivltests
 br_gh788		normal,-gno-io-range-error,-Wno-anachronisms	ivltests gold=br_gh788.gold
 br_gh793		normal			ivltests
+br_gh827		normal			ivltests gold=br_gh827.gold
 br_ml20150315		normal			ivltests gold=br_ml_20150315.gold
 br_ml20150321		CE			ivltests
 br_mw20171108		normal			ivltests
@@ -1646,6 +1647,8 @@ string9			normal			ivltests gold=string9.gold
 string10		normal			ivltests gold=string10.gold
 string11		normal			ivltests gold=string11.gold
 string12		normal			ivltests
+string13		normal			ivltests
+string14		normal			ivltests
 supply1			normal			ivltests
 supply2			normal			ivltests
 switch_primitives	normal			ivltests gold=switch_primitives.gold