Track filename and line number where variables are defined.

src/types.h

@@ -107,6 +107,8 @@ typedef struct var {
     char preserve;
     char is_constant;
     char used_since_set;
+    char const *filename;
+    int lineno;
     Value v;
 } Var;
 

src/var.c

@@ -601,6 +601,8 @@ int SetVar(char const *str, Value const *val, int nonconst_expr)
     v->v = *val;
     v->is_constant = ! nonconst_expr;
     v->used_since_set = 0;
+    v->filename = GetCurrentFilename();
+    v->lineno = LineNo;
     return OK;
 }
 
@@ -843,7 +845,7 @@ void DumpUnusedVars(void)
             fprintf(ErrFp, "%s\n", tr("The following variables were set, but not subsequently used:"));
             done_header = 1;
         }
-        fprintf(ErrFp, "\t%s\n", v->name);
+        fprintf(ErrFp, "\t%s - defined at %s:%d\n", v->name, v->filename, v->lineno);
     }
 }
 

tests/test.cmp

@@ -38716,6 +38716,6 @@ utctolocal(2050-11-06@04:00) => 2050-11-06@00:00
 utctolocal(2050-11-06@07:00) => 2050-11-06@02:00
 No reminders.
 The following variables were set, but not subsequently used:
-	b
-	d
+	b - defined at -stdin-:2
+	d - defined at -stdin-:5
 No reminders.