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Add "fallthrough" keyword, require a flow statement to end case blocks.

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Case blocks in switch statements now must end in a break, return, or
fallthrough statement to give best mix of safety, readability, and
flexibility.

The new fallthrough keyword explicitly allows control to be passed to the
next case block in a switch statement.

Addresses #754.
This commit is contained in:
Jon Siwek 2013-01-16 16:17:17 -06:00
parent 8695053e27
commit be71a42f4c
8 changed files with 150 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

1
src/SerialTypes.h
View file

@ -171,6 +171,7 @@ SERIAL_STMT(EVENT_BODY_LIST, 16)
SERIAL_STMT(INIT_STMT, 17)
SERIAL_STMT(NULL_STMT, 18)
SERIAL_STMT(WHEN_STMT, 19)
SERIAL_STMT(FALLTHROUGH_STMT, 20)
#define SERIAL_TYPE(name, val) SERIAL_CONST(name, val, BRO_TYPE)
SERIAL_TYPE(BRO_TYPE, 1)

79
src/Stmt.cc
View file

@ -23,7 +23,7 @@ const char* stmt_name(BroStmtTag t)
"print", "event", "expr", "if", "when", "switch",
"for", "next", "break", "return", "add", "delete",
"list", "bodylist",
"<init>",
"<init>", "fallthrough",
"null",
};
@ -584,6 +584,29 @@ bool IfStmt::DoUnserialize(UnserialInfo* info)
return s2 != 0;
}
static BroStmtTag get_last_stmt_tag(const Stmt* stmt)
{
if ( ! stmt ) return STMT_NULL;
if ( stmt->Tag() != STMT_LIST ) return stmt->Tag();
const StmtList* stmts = stmt->AsStmtList();
int len = stmts->Stmts().length();
if ( len == 0 ) return STMT_LIST;
return get_last_stmt_tag(stmts->Stmts()[len - 1]);
}
Case::Case(ListExpr* c, Stmt* arg_s)
: cases(simplify_expr_list(c, SIMPLIFY_GENERAL)), s(arg_s)
{
BroStmtTag t = get_last_stmt_tag(Body());
if ( t != STMT_BREAK && t != STMT_FALLTHROUGH && t != STMT_RETURN )
Error("case block must end in break/fallthrough/return statement");
}
Case::~Case()
{
Unref(cases);
@ -701,9 +724,6 @@ SwitchStmt::SwitchStmt(Expr* index, case_list* arg_cases) :
const Case* c = (*cases)[i];
const ListExpr* le = c->Cases();
if ( ! c->Body() || c->Body()->AsStmtList()->Stmts().length() == 0 )
c->Error("empty case label body does nothing");
if ( le )
{
if ( ! le->Type()->AsTypeList()->AllMatch(e->Type(), false) )
@ -798,12 +818,18 @@ Val* SwitchStmt::DoExec(Frame* f, Val* v, stmt_flow_type& flow) const
if ( matching_label_idx == -1 )
return 0;
const Case* c = (*cases)[matching_label_idx];
for ( int i = matching_label_idx; i < cases->length(); ++i )
{
const Case* c = (*cases)[i];
flow = FLOW_NEXT;
rval = c->Body()->Exec(f, flow);
if ( flow == FLOW_BREAK )
if ( flow == FLOW_BREAK || flow == FLOW_RETURN )
break;
}
if ( flow != FLOW_RETURN )
flow = FLOW_NEXT;
return rval;
@ -1461,6 +1487,47 @@ bool BreakStmt::DoUnserialize(UnserialInfo* info)
return true;
}
Val* FallthroughStmt::Exec(Frame* /* f */, stmt_flow_type& flow) const
{
RegisterAccess();
flow = FLOW_FALLTHROUGH;
return 0;
}
int FallthroughStmt::IsPure() const
{
return 1;
}
void FallthroughStmt::Describe(ODesc* d) const
{
Stmt::Describe(d);
Stmt::DescribeDone(d);
}
TraversalCode FallthroughStmt::Traverse(TraversalCallback* cb) const
{
TraversalCode tc = cb->PreStmt(this);
HANDLE_TC_STMT_PRE(tc);
tc = cb->PostStmt(this);
HANDLE_TC_STMT_POST(tc);
}
IMPLEMENT_SERIAL(FallthroughStmt, SER_FALLTHROUGH_STMT);
bool FallthroughStmt::DoSerialize(SerialInfo* info) const
{
DO_SERIALIZE(SER_FALLTHROUGH_STMT, Stmt);
return true;
}
bool FallthroughStmt::DoUnserialize(UnserialInfo* info)
{
DO_UNSERIALIZE(Stmt);
return true;
}
ReturnStmt::ReturnStmt(Expr* arg_e) : ExprStmt(STMT_RETURN, arg_e)
{
Scope* s = current_scope();

18
src/Stmt.h
View file

@ -195,8 +195,7 @@ protected:
class Case : public BroObj {
public:
Case(ListExpr* c, Stmt* arg_s) :
cases(simplify_expr_list(c,SIMPLIFY_GENERAL)), s(arg_s) { }
Case(ListExpr* c, Stmt* arg_s);
~Case();
const ListExpr* Cases() const { return cases; }
@ -371,6 +370,21 @@ protected:
DECLARE_SERIAL(BreakStmt);
};
class FallthroughStmt : public Stmt {
public:
FallthroughStmt() : Stmt(STMT_FALLTHROUGH) { }
Val* Exec(Frame* f, stmt_flow_type& flow) const;
int IsPure() const;
void Describe(ODesc* d) const;
TraversalCode Traverse(TraversalCallback* cb) const;
protected:
DECLARE_SERIAL(FallthroughStmt);
};
class ReturnStmt : public ExprStmt {
public:
ReturnStmt(Expr* e);

4
src/StmtEnums.h
View file

@ -16,6 +16,7 @@ typedef enum {
STMT_ADD, STMT_DELETE,
STMT_LIST, STMT_EVENT_BODY_LIST,
STMT_INIT,
STMT_FALLTHROUGH,
STMT_NULL
#define NUM_STMTS (int(STMT_NULL) + 1)
} BroStmtTag;
@ -24,7 +25,8 @@ typedef enum {
FLOW_NEXT, // continue on to next statement
FLOW_LOOP, // go to top of loop
FLOW_BREAK, // break out of loop
FLOW_RETURN // return from function
FLOW_RETURN, // return from function
FLOW_FALLTHROUGH// fall through to next switch case
} stmt_flow_type;
extern const char* stmt_name(BroStmtTag t);

12
src/parse.y
View file

@ -8,8 +8,8 @@
%token TOK_ATENDIF TOK_ATELSE TOK_ATIF TOK_ATIFDEF TOK_ATIFNDEF
%token TOK_BOOL TOK_BREAK TOK_CASE TOK_CONST
%token TOK_CONSTANT TOK_COPY TOK_COUNT TOK_COUNTER TOK_DEFAULT TOK_DELETE
%token TOK_DOUBLE TOK_ELSE TOK_ENUM TOK_EVENT TOK_EXPORT TOK_FILE TOK_FOR
%token TOK_FUNCTION TOK_GLOBAL TOK_HOOK TOK_ID TOK_IF TOK_INT
%token TOK_DOUBLE TOK_ELSE TOK_ENUM TOK_EVENT TOK_EXPORT TOK_FALLTHROUGH
%token TOK_FILE TOK_FOR TOK_FUNCTION TOK_GLOBAL TOK_HOOK TOK_ID TOK_IF TOK_INT
%token TOK_INTERVAL TOK_LIST TOK_LOCAL TOK_MODULE
%token TOK_NEXT TOK_OF TOK_OPAQUE TOK_PATTERN TOK_PATTERN_TEXT
%token TOK_PORT TOK_PRINT TOK_RECORD TOK_REDEF
@ -1436,6 +1436,14 @@ stmt:
brofiler.AddStmt($$);
}
| TOK_FALLTHROUGH ';' opt_no_test
{
set_location(@1, @2);
$$ = new FallthroughStmt;
if ( ! $3 )
brofiler.AddStmt($$);
}
| TOK_RETURN ';' opt_no_test
{
set_location(@1, @2);

1
src/scan.l
View file

@ -282,6 +282,7 @@ else return TOK_ELSE;
enum return TOK_ENUM;
event return TOK_EVENT;
export return TOK_EXPORT;
fallthrough return TOK_FALLTHROUGH;
file return TOK_FILE;
for return TOK_FOR;
function return TOK_FUNCTION;

32
testing/btest/core/leaks/switch-statement.bro
View file

@ -148,18 +148,19 @@ function switch_empty(v: count): string
return "n/a";
}
function switch_break(v: count): string
function switch_fallthrough(v: count): string
{
local rval = "";
switch ( v ) {
case 1:
rval += "test";
fallthrough;
case 2:
rval += "testing";
break;
rval += "ERROR";
fallthrough;
case 3:
rval += "tested";
break;
}
return rval + "return";
}
@ -170,12 +171,16 @@ function switch_default(v: count): string
switch ( v ) {
case 1:
rval += "1";
fallthrough;
case 2:
rval += "2";
break;
case 3:
rval += "3";
fallthrough;
default:
rval += "d";
break;
}
return rval + "r";
}
@ -186,13 +191,16 @@ function switch_default_placement(v: count): string
switch ( v ) {
case 1:
rval += "1";
fallthrough;
default:
rval += "d";
fallthrough;
case 2:
rval += "2";
break;
case 3:
rval += "3";
break;
}
return rval + "r";
}
@ -252,17 +260,17 @@ event new_connection(c: connection)
test_switch( switch_subnet([fe80::1]/96) , "[fe80::0]" );
test_switch( switch_subnet(192.168.1.100/16) , "192.168.0.0/16" );
test_switch( switch_empty(2) , "n/a" );
test_switch( switch_break(1) , "testreturn" );
test_switch( switch_break(2) , "testingreturn" );
test_switch( switch_break(3) , "testedreturn" );
test_switch( switch_default(1) , "1r" );
test_switch( switch_fallthrough(1) , "testtestingtestedreturn" );
test_switch( switch_fallthrough(2) , "testingtestedreturn" );
test_switch( switch_fallthrough(3) , "testedreturn" );
test_switch( switch_default(1) , "12r" );
test_switch( switch_default(2) , "2r" );
test_switch( switch_default(3) , "3r" );
test_switch( switch_default(3) , "3dr" );
test_switch( switch_default(4) , "dr" );
test_switch( switch_default_placement(1) , "1r" );
test_switch( switch_default_placement(1) , "1d2r" );
test_switch( switch_default_placement(2) , "2r" );
test_switch( switch_default_placement(3) , "3r" );
test_switch( switch_default_placement(4) , "dr" );
test_switch( switch_default_placement(4) , "d2r" );
local v = vector(0,1,2,3,4,5,6,7,9,10);
local expect: string;
@ -272,12 +280,16 @@ event new_connection(c: connection)
switch ( v[i] ) {
case 1, 2:
expect = "1,2";
break;
case 3, 4, 5:
expect = "3,4,5";
break;
case 6, 7, 8, 9:
expect = "6,7,8,9";
break;
default:
expect = "n/a";
break;
}
test_switch( switch_case_list(v[i]) , expect );
}

32
testing/btest/language/switch-statement.bro
View file

@ -143,18 +143,19 @@ function switch_empty(v: count): string
return "n/a";
}
function switch_break(v: count): string
function switch_fallthrough(v: count): string
{
local rval = "";
switch ( v ) {
case 1:
rval += "test";
fallthrough;
case 2:
rval += "testing";
break;
rval += "ERROR";
fallthrough;
case 3:
rval += "tested";
break;
}
return rval + "return";
}
@ -165,12 +166,16 @@ function switch_default(v: count): string
switch ( v ) {
case 1:
rval += "1";
fallthrough;
case 2:
rval += "2";
break;
case 3:
rval += "3";
fallthrough;
default:
rval += "d";
break;
}
return rval + "r";
}
@ -181,13 +186,16 @@ function switch_default_placement(v: count): string
switch ( v ) {
case 1:
rval += "1";
fallthrough;
default:
rval += "d";
fallthrough;
case 2:
rval += "2";
break;
case 3:
rval += "3";
break;
}
return rval + "r";
}
@ -247,17 +255,17 @@ event bro_init()
test_switch( switch_subnet([fe80::1]/96) , "[fe80::0]" );
test_switch( switch_subnet(192.168.1.100/16) , "192.168.0.0/16" );
test_switch( switch_empty(2) , "n/a" );
test_switch( switch_break(1) , "testreturn" );
test_switch( switch_break(2) , "testingreturn" );
test_switch( switch_break(3) , "testedreturn" );
test_switch( switch_default(1) , "1r" );
test_switch( switch_fallthrough(1) , "testtestingtestedreturn" );
test_switch( switch_fallthrough(2) , "testingtestedreturn" );
test_switch( switch_fallthrough(3) , "testedreturn" );
test_switch( switch_default(1) , "12r" );
test_switch( switch_default(2) , "2r" );
test_switch( switch_default(3) , "3r" );
test_switch( switch_default(3) , "3dr" );
test_switch( switch_default(4) , "dr" );
test_switch( switch_default_placement(1) , "1r" );
test_switch( switch_default_placement(1) , "1d2r" );
test_switch( switch_default_placement(2) , "2r" );
test_switch( switch_default_placement(3) , "3r" );
test_switch( switch_default_placement(4) , "dr" );
test_switch( switch_default_placement(4) , "d2r" );
local v = vector(0,1,2,3,4,5,6,7,9,10);
local expect: string;
@ -267,12 +275,16 @@ event bro_init()
switch ( v[i] ) {
case 1, 2:
expect = "1,2";
break;
case 3, 4, 5:
expect = "3,4,5";
break;
case 6, 7, 8, 9:
expect = "6,7,8,9";
break;
default:
expect = "n/a";
break;
}
test_switch( switch_case_list(v[i]) , expect );
}