From 45bef16be0fe9d8b760bc91c463bbcdf9f601b04 Mon Sep 17 00:00:00 2001
From: Robin Sommer <robin@corelight.com>
Date: Tue, 18 Aug 2020 10:31:16 +0000
Subject: [PATCH] Catch if &add_func/&delete_func is applied to IDs that don't
 have values.

We do to allow adding &add_func to a global that's not immediately
initialized, as a later redef may fix that.

Closes #467.
---
 src/ID.cc                                         |  7 +++++++
 .../Baseline/language.global-unset-addto/output   |  2 ++
 testing/btest/language/global-unset-addto.zeek    | 15 +++++++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 testing/btest/Baseline/language.global-unset-addto/output
 create mode 100644 testing/btest/language/global-unset-addto.zeek

diff --git a/src/ID.cc b/src/ID.cc
index 03f15e1f78..2f9852770d 100644
--- a/src/ID.cc
+++ b/src/ID.cc
@@ -220,6 +220,13 @@ void ID::SetVal(ExprPtr ev, InitClass c)
 	if ( ! a )
 		Internal("no add/delete function in ID::SetVal");
 
+	if ( ! val )
+		{
+		Error(fmt("%s initializer applied to ID without value",
+		      (c == INIT_EXTRA ? "+=" : "-="), this);
+		return;
+		}
+
 	EvalFunc(a->GetExpr(), std::move(ev));
 	}
 
diff --git a/testing/btest/Baseline/language.global-unset-addto/output b/testing/btest/Baseline/language.global-unset-addto/output
new file mode 100644
index 0000000000..306f0afddb
--- /dev/null
+++ b/testing/btest/Baseline/language.global-unset-addto/output
@@ -0,0 +1,2 @@
+error in /Users/robin/bro/master/testing/btest/.tmp/language.global-unset-addto/global-unset-addto.zeek, line 4: += initializer applied to ID without value (a)
+error in /Users/robin/bro/master/testing/btest/.tmp/language.global-unset-addto/global-unset-addto.zeek, line 5: -= initializer applied to ID without value (b)
diff --git a/testing/btest/language/global-unset-addto.zeek b/testing/btest/language/global-unset-addto.zeek
new file mode 100644
index 0000000000..bf2f794809
--- /dev/null
+++ b/testing/btest/language/global-unset-addto.zeek
@@ -0,0 +1,15 @@
+# @TEST-EXEC-FAIL: zeek -b %INPUT  >output 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff output
+
+global a: count &add_func = function(old: count, new: count): count { return 3; };
+global b: count &delete_func = function(old: count, new: count): count { return 3; };
+
+redef a += 13;
+redef b -= 13;
+
+# The following is ok.
+global c: count &redef &add_func = function(old: count, new: count): count { return 3; };
+redef c = 0;
+redef c += 13;
+
+