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Fix uninitialized locals in event/hook handlers from having a value.

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Since values for local variables are referenced by offset within a Frame
(not by identifier name), and event/hook handler bodies share a common
Frame, the value offsets for local variables in different handlers may
overlap.  This meant locals in a handler without an initialization may
actually end up referring to the value of a previous handler's local
that has the same Frame offset.  When executing the body, that can
possibly result in a type-conflict error or give give unexpected
results instead of a "use of uninitialized value" error.

This patch makes it so uninitialized locals do always refer to a null
value before executing the body of a event/hook handler, so that using
them without assigning a value within the body will connsistently give
a "use of uninitialized value" error.

Addresses #932.
This commit is contained in:
Jon Siwek 2013-01-17 15:21:50 -06:00
parent 564e27abb6
commit 0a69b87f03
4 changed files with 38 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

16
src/Stmt.cc
View file

@ -1789,13 +1789,21 @@ Val* InitStmt::Exec(Frame* f, stmt_flow_type& flow) const
ID* aggr = (*inits)[i];
BroType* t = aggr->Type();
Val* v;
if ( t->Tag() == TYPE_RECORD )
Val* v = 0;
switch ( t->Tag() ) {
case TYPE_RECORD:
v = new RecordVal(t->AsRecordType());
else if ( aggr->Type()->Tag() == TYPE_VECTOR )
break;
case TYPE_VECTOR:
v = new VectorVal(t->AsVectorType());
else
break;
case TYPE_TABLE:
v = new TableVal(t->AsTableType(), aggr->Attrs());
break;
default:
break;
}
f->SetElement(aggr->Offset(), v);
}

5
src/Var.cc
View file

@ -243,10 +243,7 @@ Stmt* add_local(ID* id, BroType* t, init_class c, Expr* init,
else
{
if ( t->Tag() == TYPE_RECORD || t->Tag() == TYPE_TABLE ||
t->Tag() == TYPE_VECTOR )
current_scope()->AddInit(id);
current_scope()->AddInit(id);
return new NullStmt;
}
}

2
testing/btest/Baseline/language.uninitialized-local/out Normal file
View file

@ -0,0 +1,2 @@
error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.uninitialized-local/uninitialized-local.bro, line 16: value used but not set (my_string)
Continuing

23
testing/btest/language/uninitialized-local.bro Normal file
View file

@ -0,0 +1,23 @@
# @TEST-EXEC: bro -b %INPUT >out 2>&1
# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
event testit() &priority=10
{
local my_count: count = 10;
}
event testit()
{
# my_string's value occupies same Frame offset as my_count's from above
# handler, but execution of this handler body should still "initialize"
# it to a null value instead of referring to a left-over value of my_count.
local my_string: string;
local my_vector: vector of string;
my_vector[0] = my_string;
print "Continuing";
}
event bro_init()
{
event testit();
}