From 46e300b2c5b5d9a1033bf8be94f8fb1a20992f60 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Sat, 23 Sep 2017 18:03:39 -0400
Subject: [PATCH] Add --getenv option.

---
 Changes                         |  2 ++
 bin/verilator                   | 17 +++++++++++++----
 src/V3Options.cpp               | 17 +++++++++++++++++
 src/V3Options.h                 |  1 +
 test_regress/t/t_flag_getenv.pl | 25 +++++++++++++++++++++++++
 test_regress/t/t_flag_getenv.v  |  6 ++++++
 6 files changed, 64 insertions(+), 4 deletions(-)
 create mode 100755 test_regress/t/t_flag_getenv.pl
 create mode 100644 test_regress/t/t_flag_getenv.v

diff --git a/Changes b/Changes
index 47d4a3257..417d83f58 100644
--- a/Changes
+++ b/Changes
@@ -4,6 +4,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 * Verilator 3.913 devel
 
+***   Add --getenv option.
+
 ****  The internal test_verilated test directory is moved to be part of test_regress.
 
 
diff --git a/bin/verilator b/bin/verilator
index e8178b299..7b929bd99 100755
--- a/bin/verilator
+++ b/bin/verilator
@@ -286,6 +286,7 @@ descriptions in the next sections for more information.
      -G<name>=<value>           Overwrite toplevel parameter
     --gdb                       Run Verilator under GDB interactively
     --gdbbt                     Run Verilator under GDB for backtrace
+    --getenv <var>              Get environment variable with defaults
     --help                      Display this help
      -I<dir>                    Directory to search for includes
     --if-depth <value>          Tune IFDEPTH warning
@@ -762,6 +763,14 @@ backtrace on exit, then exit GDB immediately.  Without --debug or if GDB
 doesn't seem to work, this flag is ignored.  Intended for easy creation of
 backtraces by users; otherwise see the --gdb flag.
 
+=item --getenv I<variable>
+
+If the variable is declared in the environment, print it and exit
+immediately. Otherwise, if it's built into Verilator (e.g. VERILATOR_ROOT),
+print that and exit immediately. Otherwise, print a newline and exit
+immediately. This can be useful in makefiles. See also -V, and the various
+*.mk files.
+
 =item --help
 
 Displays this message and program version and exits.
@@ -1181,7 +1190,7 @@ Setting it to "" disables matching.
 =item -V
 
 Shows the verbose version, including configuration information compiled
-into Verilator.  (Similar to perl -V.)
+into Verilator.  (Similar to perl -V.)  See also --getenv.
 
 =item -v I<filename>
 
@@ -1409,8 +1418,8 @@ And we get as output
 
 Really, you're better off writing a Makefile to do all this for you.  Then,
 when your source changes it will automatically run all of these steps; to
-aid this Verilator can create a makefile dependency file.  See the test_c
-directory in the distribution for an example.
+aid this Verilator can create a makefile dependency file.  See the examples
+directory in the distribution.
 
 
 =head1 EXAMPLE SYSTEMC EXECUTION
@@ -1487,7 +1496,7 @@ And we get the same output as the C++ example:
 
 Really, you're better off using a Makefile to do all this for you.  Then,
 when your source changes it will automatically run all of these steps.  See
-the test_sc directory in the distribution for an example.
+the examples directory in the distribution.
 
 
 =head1 BENCHMARKING & OPTIMIZATION
diff --git a/src/V3Options.cpp b/src/V3Options.cpp
index 1ea4a7a8b..6f0802380 100644
--- a/src/V3Options.cpp
+++ b/src/V3Options.cpp
@@ -410,6 +410,18 @@ V3LangCode V3Options::fileLanguage(const string &filename) {
 //######################################################################
 // Environment
 
+string V3Options::getenvBuiltins(const string& var) {
+    if (var == "PERL") return getenvPERL();
+    else if (var == "SYSTEMC") return getenvSYSTEMC();
+    else if (var == "SYSTEMC_ARCH") return getenvSYSTEMC_ARCH();
+    else if (var == "SYSTEMC_INCLUDE") return getenvSYSTEMC_INCLUDE();
+    else if (var == "SYSTEMC_LIBDIR") return getenvSYSTEMC_LIBDIR();
+    else if (var == "VERILATOR_ROOT") return getenvVERILATOR_ROOT();
+    else {
+	return V3Os::getenvStr(var,"");
+    }
+}
+
 string V3Options::getenvPERL() {
     return V3Os::getenvStr("PERL","perl");
 }
@@ -762,6 +774,11 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc, char
 	    else if ( !strncmp (sw, "-G", strlen("-G"))) {
 		addParameter(string (sw+strlen("-G")), false);
 	    }
+	    else if ( !strcmp (sw, "-getenv") && (i+1)<argc ) {
+		shift;
+		cout<<V3Options::getenvBuiltins(argv[i])<<endl;
+		exit(0);
+	    }
 	    else if ( !strncmp (sw, "-I", 2)) {
 		addIncDirUser(parseFileArg(optdir, string (sw+strlen("-I"))));
 	    }
diff --git a/src/V3Options.h b/src/V3Options.h
index 44cf65bde..f37082191 100644
--- a/src/V3Options.h
+++ b/src/V3Options.h
@@ -329,6 +329,7 @@ class V3Options {
     // Most of these may be built into the executable with --enable-defenv,
     // see the README.  If adding new variables, also see src/Makefile_obj.in
     // Also add to V3Options::showVersion()
+    static string getenvBuiltins(const string& var);
     static string getenvPERL();
     static string getenvSYSTEMC();
     static string getenvSYSTEMC_ARCH();
diff --git a/test_regress/t/t_flag_getenv.pl b/test_regress/t/t_flag_getenv.pl
new file mode 100755
index 000000000..37a20b3ac
--- /dev/null
+++ b/test_regress/t/t_flag_getenv.pl
@@ -0,0 +1,25 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2008 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+$Self->{vlt} or $Self->skip("Verilator only test");
+
+$ENV{FOOBARTEST} = "gotit";
+
+compile (
+	 v_flags2 => ["--getenv FOOBARTEST"],
+	 expect=>
+'gotit
+',
+	 make_top_shell => 0,
+	 make_main => 0,
+	 verilator_make_gcc => 0,
+	 );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_flag_getenv.v b/test_regress/t/t_flag_getenv.v
new file mode 100644
index 000000000..99a0ead12
--- /dev/null
+++ b/test_regress/t/t_flag_getenv.v
@@ -0,0 +1,6 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2008 by Wilson Snyder.
+
+`define EMPTY 1