renamed ED hook register to "ED" and protect ED hook executions

SciTECO commands usually only take parameters from the stack that
they need. Without protecting the ED hook execution with brace operators,
additional arguments not consumed by the hook-dispatching command
are passed into the ED hook invocation. Also an ED hook macro could
leave additional values on the expression stack (by accident).
All of this may lead to undefined behaviour if ED hooks
are involved.

1 files changed, 22 insertions, 1 deletions

diff --git a/src/qregisters.cpp b/src/qregisters.cpp
index 223a707..89b2afd 100644
--- a/src/qregisters.cpp
+++ b/src/qregisters.cpp
@@ -366,11 +366,32 @@ QRegisterStack::~QRegisterStack()
 void
 QRegisters::hook(Hook type)
 {
+	QRegister *reg;
+
 	if (!(Flags::ed & Flags::ED_HOOKS))
 		return;
 
+	reg = globals["ED"];
+	if (!reg)
+		throw Error("Undefined ED-hook register (\"ED\")");
+
+	/*
+	 * ED-hook execution should not see any
+	 * integer parameters but the hook type.
+	 * Such parameters could confuse the ED macro
+	 * and macro authors do not expect side effects
+	 * of ED macros on the expression stack.
+	 * Also make sure it does not leave behind
+	 * additional arguments on the stack.
+	 *
+	 * So this effectively executes:
+	 * (typeM[ED]^[)
+	 */
+	expressions.push(Expressions::OP_BRACE);
 	expressions.push(type);
-	globals["0"]->execute();
+	reg->execute();
+	expressions.discard_args();
+	expressions.eval(true);
 }
 
 void