Error out on empty variable names

In #83 we followed Make's example and accepted empty target-specific
variable names, but now, with Make 4.1, it's an error.

Test: run test suite on ubuntu 18.04 which has Make 4.1
Change-Id: I55211ca1130ce855e9242b6e03401a55b69d2a73

3 files changed, 5 insertions, 21 deletions

diff --git a/eval.cc b/eval.cc
index aaad21f..3772763 100644
--- a/eval.cc
+++ b/eval.cc
@@ -300,26 +300,10 @@ void Evaluator::EvalRule(const RuleStmt* stmt) {
     return;
   }
 
-  // "test: =foo" is questionable but a valid rule definition (not a
-  // target specific variable).
-  // See https://github.com/google/kati/issues/83
-  string buf;
   if (!separator_pos) {
-    KATI_WARN_LOC(loc_,
-                  "defining a target which starts with `=', "
-                  "which is not probably what you meant");
-    buf = after_targets.as_string();
-    if (stmt->sep == RuleStmt::SEP_SEMICOLON) {
-      buf += ';';
-    } else if (stmt->sep == RuleStmt::SEP_EQ ||
-               stmt->sep == RuleStmt::SEP_FINALEQ) {
-      buf += '=';
-    }
-    if (stmt->rhs) {
-      buf += stmt->rhs->Eval(this);
-    }
-    after_targets = buf;
-    separator_pos = string::npos;
+    // We used to make this a warning and otherwise accept it, but Make 4.1
+    // calls this out as an error, so let's follow.
+    Error("*** empty variable name.");
   }
 
   Rule* rule = new Rule();
diff --git a/testcase/empty_target_specific_var.mk b/testcase/empty_target_specific_var.mk
index fd9e6c1..5683eb2 100644
--- a/testcase/empty_target_specific_var.mk
+++ b/testcase/empty_target_specific_var.mk
@@ -4,4 +4,4 @@ test: =foo
 
 var==foo
 $(var):
-	echo PASS
+	echo FAIL
diff --git a/testcase/empty_target_specific_var2.mk b/testcase/empty_target_specific_var2.mk
index 6defb52..960a615 100644
--- a/testcase/empty_target_specific_var2.mk
+++ b/testcase/empty_target_specific_var2.mk
@@ -8,4 +8,4 @@ $(call var)
 
 eq_one:==1
 $(eq_one):
-	echo PASS
+	echo FAIL