From d2a8fa74409d5fc35db36b67fd15aa0dbccbf0f4 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Wed, 17 Nov 2021 17:46:08 -0500
Subject: [PATCH] Fix display of empty string constant (#3207).

---
 Changes                      |  1 +
 src/V3Number.h               |  1 +
 src/verilog.y                | 10 +++++++++-
 test_regress/t/t_display.out |  1 +
 test_regress/t/t_display.v   |  1 +
 5 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Changes b/Changes
index 8b62759f9..8c089b387 100644
--- a/Changes
+++ b/Changes
@@ -22,6 +22,7 @@ Verilator 4.215 devel
 * Fix array method names with parenthesis (#3181) (#3183). [Teng Huang]
 * Fix split_var assign merging (#3177) (#3179). [Yutetsu TAKATSUKASA]
 * Fix nested generate if genblk naming (#3189). [yanx21]
+* Fix display of empty string constant (#3207). [Julie Schwartz]
 
 
 Verilator 4.214 2021-10-17
diff --git a/src/V3Number.h b/src/V3Number.h
index f43fd6619..e62ad8562 100644
--- a/src/V3Number.h
+++ b/src/V3Number.h
@@ -233,6 +233,7 @@ public:
     V3Number(String, AstNode* nodep, const string& value) {
         init(nodep, 0);
         setString(value);
+        m_fromString = true;
     }
     class Null {};
     V3Number(Null, AstNode* nodep) {
diff --git a/src/verilog.y b/src/verilog.y
index 7d6e44d16..18779d05e 100644
--- a/src/verilog.y
+++ b/src/verilog.y
@@ -5006,7 +5006,15 @@ str<strp>:			// yaSTRING but with \{escapes} need decoded
 
 strAsInt<nodep>:
 		yaSTRING
-			{ $$ = new AstConst{$<fl>1, AstConst::VerilogStringLiteral(), GRAMMARP->deQuote($<fl>1, *$1)}; }
+			{ if ($1->empty()) {
+			      // else "" is not representable as number as is width 0
+                              // TODO all strings should be represented this way
+			      // until V3Width converts as/if needed to a numerical constant
+			      $$ = new AstConst{$<fl>1, AstConst::String{}, GRAMMARP->deQuote($<fl>1, *$1)};
+			  } else {
+			      $$ = new AstConst{$<fl>1, AstConst::VerilogStringLiteral(), GRAMMARP->deQuote($<fl>1, *$1)};
+			  }
+			}
 	;
 
 strAsIntIgnore<nodep>:		// strAsInt, but never matches for when expr shouldn't parse strings
diff --git a/test_regress/t/t_display.out b/test_regress/t/t_display.out
index 0475a1952..5b3ba2aa9 100644
--- a/test_regress/t/t_display.out
+++ b/test_regress/t/t_display.out
@@ -56,6 +56,7 @@ hello, from a concatenated string.
 hello, from a concatenated format string [0].
 extra argument:                    0
                    0 : pre argument after
+empty: ><
 [0] Embedded tab '	' and <#013> return
 [0] Embedded
 multiline
diff --git a/test_regress/t/t_display.v b/test_regress/t/t_display.v
index 3f191f9b1..fa280f616 100644
--- a/test_regress/t/t_display.v
+++ b/test_regress/t/t_display.v
@@ -149,6 +149,7 @@ module t;
       $write("hel", "lo, fr", "om a concatenated format string [%0t].\n", $time);
       $display("extra argument: ", $time);
       $display($time,, ": pre argument",, "after");
+      $display("empty: >%s<", "");
       $write("[%0t] Embedded tab '\t' and \r return\n", $time);
       $display("[%0t] Embedded\
 multiline", $time);