From 4eb280601ea6ec14e1ad2387af3cb8a8906f3f44 Mon Sep 17 00:00:00 2001
From: Todd Strader <tstrader@hudson-trading.com>
Date: Thu, 9 Feb 2023 10:09:00 -0500
Subject: [PATCH] handle constant format field widths (#3946)

---
 src/V3Simulate.h                     | 9 ++++++++-
 test_regress/t/t_const_string_func.v | 5 ++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/V3Simulate.h b/src/V3Simulate.h
index 90f846cfb..d6ea92e26 100644
--- a/src/V3Simulate.h
+++ b/src/V3Simulate.h
@@ -1084,12 +1084,19 @@ private:
             const string format = nodep->text();
             auto pos = format.cbegin();
             bool inPct = false;
+            string width;
             for (; pos != format.cend(); ++pos) {
                 if (!inPct && pos[0] == '%') {
                     inPct = true;
+                    width = "";
                 } else if (!inPct) {  // Normal text
                     result += *pos;
                 } else {  // Format character
+                    if (std::isdigit(pos[0])) {
+                        width += pos[0];
+                        continue;
+                    }
+
                     inPct = false;
 
                     if (V3Number::displayedFmtLegal(tolower(pos[0]), false)) {
@@ -1101,7 +1108,7 @@ private:
                                 nodep, "Argument for $display like statement is not constant");
                             break;
                         }
-                        const string pformat = std::string{"%"} + pos[0];
+                        const string pformat = std::string{"%"} + width + pos[0];
                         result += constp->num().displayed(nodep, pformat);
                     } else {
                         switch (tolower(pos[0])) {
diff --git a/test_regress/t/t_const_string_func.v b/test_regress/t/t_const_string_func.v
index c3ed6d12b..d410d7a27 100644
--- a/test_regress/t/t_const_string_func.v
+++ b/test_regress/t/t_const_string_func.v
@@ -8,12 +8,15 @@ module t ();
 
    function automatic string foo_func();
       foo_func = "FOO";
+      foo_func = $sformatf("%sBAR", foo_func);
+      for (int i = 0; i < 4; i++)
+         foo_func = $sformatf("%s%0d", foo_func, i);
    endfunction
 
    localparam string the_foo = foo_func();
 
    initial begin
-      if (the_foo != "FOO") $stop;
+      if (the_foo != "FOOBAR0123") $stop;
       $write("*-* All Finished *-*\n");
       $finish;
    end