diff -Naur acpica-unix2-20191213.orig/source/compiler/dtcompiler.h acpica-unix2-20191213/source/compiler/dtcompiler.h
--- acpica-unix2-20191213.orig/source/compiler/dtcompiler.h	2020-02-23 18:05:24.257395129 -0700
+++ acpica-unix2-20191213/source/compiler/dtcompiler.h	2020-02-23 18:06:42.956236378 -0700
@@ -351,7 +351,7 @@
 
 /* dtparser - lex/yacc files */
 
-UINT64                      DtCompilerParserResult; /* Expression return value */
+extern UINT64                      DtCompilerParserResult; /* Expression return value */
 int
 DtCompilerParserparse (
     void);
diff -Naur acpica-unix2-20191213.orig/source/compiler/aslcompiler.l acpica-unix2-20191213/source/compiler/aslcompiler.l
--- acpica-unix2-20191213.orig/source/compiler/aslcompiler.l	2019-12-13 08:58:18.000000000 -0700
+++ acpica-unix2-20191213/source/compiler/aslcompiler.l	2020-02-24 15:08:53.067560139 -0700
@@ -48,7 +48,7 @@
 
 #include <stdlib.h>
 #include <string.h>
-YYSTYPE AslCompilerlval;
+extern YYSTYPE AslCompilerlval;
 
 /*
  * Generation:  Use the following command line:
diff -Naur acpica-unix2-20191213.orig/source/compiler/prparser.l acpica-unix2-20191213/source/compiler/prparser.l
--- acpica-unix2-20191213.orig/source/compiler/prparser.l	2019-12-13 08:58:19.000000000 -0700
+++ acpica-unix2-20191213/source/compiler/prparser.l	2020-02-24 15:09:25.909839732 -0700
@@ -116,7 +116,7 @@
 /*
  * Local support functions
  */
-YY_BUFFER_STATE         LexBuffer;
+extern YY_BUFFER_STATE         LexBuffer;
 
 
 /******************************************************************************