The Go language has clarified the use of goto. It is now invalid to use
goto to jump into an inner block, and to use goto to jump across a
variable declaration. This patch to the Go frontend implements these
restrictions, and adjust one library and a few test cases accordingly.
Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.
Ian
Index: gcc/go/gofrontend/gogo.cc
===================================================================
--- gcc/go/gofrontend/gogo.cc (revision 179010)
+++ gcc/go/gofrontend/gogo.cc (working copy)
@@ -857,7 +857,7 @@ Gogo::add_label_definition(const std::st
{
go_assert(!this->functions_.empty());
Function* func = this->functions_.back().function->func_value();
- Label* label = func->add_label_definition(label_name, location);
+ Label* label = func->add_label_definition(this, label_name, location);
this->add_statement(Statement::make_label_statement(label, location));
return label;
}
@@ -865,11 +865,21 @@ Gogo::add_label_definition(const std::st
// Add a label reference.
Label*
-Gogo::add_label_reference(const std::string& label_name)
+Gogo::add_label_reference(const std::string& label_name,
+ source_location location, bool issue_goto_errors)
{
go_assert(!this->functions_.empty());
Function* func = this->functions_.back().function->func_value();
- return func->add_label_reference(label_name);
+ return func->add_label_reference(this, label_name, location,
+ issue_goto_errors);
+}
+
+// Return the current binding state.
+
+Bindings_snapshot*
+Gogo::bindings_snapshot(source_location location)
+{
+ return new Bindings_snapshot(this->current_block(), location);
}
// Add a statement.
@@ -2843,30 +2853,24 @@ Function::is_method() const
// Add a label definition.
Label*
-Function::add_label_definition(const std::string& label_name,
+Function::add_label_definition(Gogo* gogo, const std::string& label_name,
source_location location)
{
Label* lnull = NULL;
std::pair<Labels::iterator, bool> ins =
this->labels_.insert(std::make_pair(label_name, lnull));
+ Label* label;
if (ins.second)
{
// This is a new label.
- Label* label = new Label(label_name);
- label->define(location);
+ label = new Label(label_name);
ins.first->second = label;
- return label;
}
else
{
// The label was already in the hash table.
- Label* label = ins.first->second;
- if (!label->is_defined())
- {
- label->define(location);
- return label;
- }
- else
+ label = ins.first->second;
+ if (label->is_defined())
{
error_at(location, "label %qs already defined",
Gogo::message_name(label_name).c_str());
@@ -2875,31 +2879,55 @@ Function::add_label_definition(const std
return new Label(label_name);
}
}
+
+ label->define(location, gogo->bindings_snapshot(location));
+
+ // Issue any errors appropriate for any previous goto's to this
+ // label.
+ const std::vector<Bindings_snapshot*>& refs(label->refs());
+ for (std::vector<Bindings_snapshot*>::const_iterator p = refs.begin();
+ p != refs.end();
+ ++p)
+ (*p)->check_goto_to(gogo->current_block());
+ label->clear_refs();
+
+ return label;
}
// Add a reference to a label.
Label*
-Function::add_label_reference(const std::string& label_name)
+Function::add_label_reference(Gogo* gogo, const std::string& label_name,
+ source_location location, bool issue_goto_errors)
{
Label* lnull = NULL;
std::pair<Labels::iterator, bool> ins =
this->labels_.insert(std::make_pair(label_name, lnull));
+ Label* label;
if (!ins.second)
{
// The label was already in the hash table.
- Label* label = ins.first->second;
- label->set_is_used();
- return label;
+ label = ins.first->second;
}
else
{
go_assert(ins.first->second == NULL);
- Label* label = new Label(label_name);
+ label = new Label(label_name);
ins.first->second = label;
- label->set_is_used();
- return label;
}
+
+ label->set_is_used();
+
+ if (issue_goto_errors)
+ {
+ Bindings_snapshot* snapshot = label->snapshot();
+ if (snapshot != NULL)
+ snapshot->check_goto_from(gogo->current_block(), location);
+ else
+ label->add_snapshot_ref(gogo->bindings_snapshot(location));
+ }
+
+ return label;
}
// Warn about labels that are defined but not used.
@@ -3407,6 +3435,92 @@ Block::get_backend(Translate_context* co
return ret;
}
+// Class Bindings_snapshot.
+
+Bindings_snapshot::Bindings_snapshot(const Block* b, source_location location)
+ : block_(b), counts_(), location_(location)
+{
+ while (b != NULL)
+ {
+ this->counts_.push_back(b->bindings()->size_definitions());
+ b = b->enclosing();
+ }
+}
+
+// Report errors appropriate for a goto from B to this.
+
+void
+Bindings_snapshot::check_goto_from(const Block* b, source_location loc)
+{
+ size_t dummy;
+ if (!this->check_goto_block(loc, b, this->block_, &dummy))
+ return;
+ this->check_goto_defs(loc, this->block_,
+ this->block_->bindings()->size_definitions(),
+ this->counts_[0]);
+}
+
+// Report errors appropriate for a goto from this to B.
+
+void
+Bindings_snapshot::check_goto_to(const Block* b)
+{
+ size_t index;
+ if (!this->check_goto_block(this->location_, this->block_, b, &index))
+ return;
+ this->check_goto_defs(this->location_, b, this->counts_[index],
+ b->bindings()->size_definitions());
+}
+
+// Report errors appropriate for a goto at LOC from BFROM to BTO.
+// Return true if all is well, false if we reported an error. If this
+// returns true, it sets *PINDEX to the number of blocks BTO is above
+// BFROM.
+
+bool
+Bindings_snapshot::check_goto_block(source_location loc, const Block* bfrom,
+ const Block* bto, size_t* pindex)
+{
+ // It is an error if BTO is not either BFROM or above BFROM.
+ size_t index = 0;
+ for (const Block* pb = bfrom; pb != bto; pb = pb->enclosing(), ++index)
+ {
+ if (pb == NULL)
+ {
+ error_at(loc, "goto jumps into block");
+ inform(bto->start_location(), "goto target block starts here");
+ return false;
+ }
+ }
+ *pindex = index;
+ return true;
+}
+
+// Report errors appropriate for a goto at LOC ending at BLOCK, where
+// CFROM is the number of names defined at the point of the goto and
+// CTO is the number of names defined at the point of the label.
+
+void
+Bindings_snapshot::check_goto_defs(source_location loc, const Block* block,
+ size_t cfrom, size_t cto)
+{
+ if (cfrom < cto)
+ {
+ Bindings::const_definitions_iterator p =
+ block->bindings()->begin_definitions();
+ for (size_t i = 0; i < cfrom; ++i)
+ {
+ go_assert(p != block->bindings()->end_definitions());
+ ++p;
+ }
+ go_assert(p != block->bindings()->end_definitions());
+
+ std::string n = (*p)->message_name();
+ error_at(loc, "goto jumps over declaration of %qs", n.c_str());
+ inform((*p)->location(), "%qs defined here", n.c_str());
+ }
+}
+
// Class Variable.
Variable::Variable(Type* type, Expression* init, bool is_global,
@@ -4698,6 +4812,18 @@ Bindings::traverse(Traverse* traverse, b
// Class Label.
+// Clear any references to this label.
+
+void
+Label::clear_refs()
+{
+ for (std::vector<Bindings_snapshot*>::iterator p = this->refs_.begin();
+ p != this->refs_.end();
+ ++p)
+ delete *p;
+ this->refs_.clear();
+}
+
// Get the backend representation for a label.
Blabel*
Index: gcc/go/gofrontend/gogo.h
===================================================================
--- gcc/go/gofrontend/gogo.h (revision 178784)
+++ gcc/go/gofrontend/gogo.h (working copy)
@@ -22,6 +22,7 @@ class Temporary_statement;
class Block;
class Function;
class Bindings;
+class Bindings_snapshot;
class Package;
class Variable;
class Pointer_type;
@@ -246,6 +247,10 @@ class Gogo
Named_object*
current_function() const;
+ // Return the current block.
+ Block*
+ current_block();
+
// Start a new block. This is not initially associated with a
// function.
void
@@ -269,9 +274,16 @@ class Gogo
Label*
add_label_definition(const std::string&, source_location);
- // Add a label reference.
+ // Add a label reference. ISSUE_GOTO_ERRORS is true if we should
+ // report errors for a goto from the current location to the label
+ // location.
Label*
- add_label_reference(const std::string&);
+ add_label_reference(const std::string&, source_location,
+ bool issue_goto_errors);
+
+ // Return a snapshot of the current binding state.
+ Bindings_snapshot*
+ bindings_snapshot(source_location);
// Add a statement to the current block.
void
@@ -551,10 +563,6 @@ class Gogo
const Bindings*
current_bindings() const;
- // Return the current block.
- Block*
- current_block();
-
// Get the name of the magic initialization function.
const std::string&
get_init_fn_name();
@@ -833,11 +841,14 @@ class Function
// Add a label definition to the function.
Label*
- add_label_definition(const std::string& label_name, source_location);
+ add_label_definition(Gogo*, const std::string& label_name, source_location);
- // Add a label reference to a function.
+ // Add a label reference to a function. ISSUE_GOTO_ERRORS is true
+ // if we should report errors for a goto from the current location
+ // to the label location.
Label*
- add_label_reference(const std::string& label_name);
+ add_label_reference(Gogo*, const std::string& label_name,
+ source_location, bool issue_goto_errors);
// Warn about labels that are defined but not used.
void
@@ -980,6 +991,40 @@ class Function
bool has_recover_thunk_;
};
+// A snapshot of the current binding state.
+
+class Bindings_snapshot
+{
+ public:
+ Bindings_snapshot(const Block*, source_location);
+
+ // Report any errors appropriate for a goto from the current binding
+ // state of B to this one.
+ void
+ check_goto_from(const Block* b, source_location);
+
+ // Report any errors appropriate for a goto from this binding state
+ // to the current state of B.
+ void
+ check_goto_to(const Block* b);
+
+ private:
+ bool
+ check_goto_block(source_location, const Block*, const Block*, size_t*);
+
+ void
+ check_goto_defs(source_location, const Block*, size_t, size_t);
+
+ // The current block.
+ const Block* block_;
+ // The number of names currently defined in each open block.
+ // Element 0 is this->block_, element 1 is
+ // this->block_->enclosing(), etc.
+ std::vector<size_t> counts_;
+ // The location where this snapshot was taken.
+ source_location location_;
+};
+
// A function declaration.
class Function_declaration
@@ -2108,7 +2153,8 @@ class Label
{
public:
Label(const std::string& name)
- : name_(name), location_(0), is_used_(false), blabel_(NULL)
+ : name_(name), location_(0), snapshot_(NULL), refs_(), is_used_(false),
+ blabel_(NULL)
{ }
// Return the label's name.
@@ -2136,12 +2182,36 @@ class Label
location() const
{ return this->location_; }
- // Define the label at LOCATION.
+ // Return the bindings snapshot.
+ Bindings_snapshot*
+ snapshot() const
+ { return this->snapshot_; }
+
+ // Add a snapshot of a goto which refers to this label.
void
- define(source_location location)
+ add_snapshot_ref(Bindings_snapshot* snapshot)
{
go_assert(this->location_ == 0);
+ this->refs_.push_back(snapshot);
+ }
+
+ // Return the list of snapshots of goto statements which refer to
+ // this label.
+ const std::vector<Bindings_snapshot*>&
+ refs() const
+ { return this->refs_; }
+
+ // Clear the references.
+ void
+ clear_refs();
+
+ // Define the label at LOCATION with the given bindings snapshot.
+ void
+ define(source_location location, Bindings_snapshot* snapshot)
+ {
+ go_assert(this->location_ == 0 && this->snapshot_ == NULL);
this->location_ = location;
+ this->snapshot_ = snapshot;
}
// Return the backend representation for this label.
@@ -2160,6 +2230,11 @@ class Label
// The location of the definition. This is 0 if the label has not
// yet been defined.
source_location location_;
+ // A snapshot of the set of bindings defined at this label, used to
+ // issue errors about invalid goto statements.
+ Bindings_snapshot* snapshot_;
+ // A list of snapshots of goto statements which refer to this label.
+ std::vector<Bindings_snapshot*> refs_;
// Whether the label has been used.
bool is_used_;
// The backend representation.
Index: gcc/go/gofrontend/parse.cc
===================================================================
--- gcc/go/gofrontend/parse.cc (revision 179010)
+++ gcc/go/gofrontend/parse.cc (working copy)
@@ -3813,7 +3813,8 @@ Parse::return_stat()
this->gogo_->add_statement(Statement::make_return_statement(vals, location));
}
-// IfStmt = "if" [ SimpleStmt ";" ] Expression Block [ "else" Statement ] .
+// IfStmt = "if" [ SimpleStmt ";" ] Expression Block
+// [ "else" ( IfStmt | Block ) ] .
void
Parse::if_stat()
@@ -3883,10 +3884,17 @@ Parse::if_stat()
Block* else_block = NULL;
if (this->peek_token()->is_keyword(KEYWORD_ELSE))
{
- this->advance_token();
- // We create a block to gather the statement.
this->gogo_->start_block(this->location());
- this->statement(NULL);
+ const Token* token = this->advance_token();
+ if (token->is_keyword(KEYWORD_IF))
+ this->if_stat();
+ else if (token->is_op(OPERATOR_LCURLY))
+ this->block();
+ else
+ {
+ error_at(this->location(), "expected %<if%> or %<{%>");
+ this->statement(NULL);
+ }
else_block = this->gogo_->finish_block(this->location());
}
@@ -4914,7 +4922,7 @@ Parse::break_stat()
{
// If there is a label with this name, mark it as used to
// avoid a useless error about an unused label.
- this->gogo_->add_label_reference(token->identifier());
+ this->gogo_->add_label_reference(token->identifier(), 0, false);
error_at(token->location(), "invalid break label %qs",
Gogo::message_name(token->identifier()).c_str());
@@ -4969,7 +4977,7 @@ Parse::continue_stat()
{
// If there is a label with this name, mark it as used to
// avoid a useless error about an unused label.
- this->gogo_->add_label_reference(token->identifier());
+ this->gogo_->add_label_reference(token->identifier(), 0, false);
error_at(token->location(), "invalid continue label %qs",
Gogo::message_name(token->identifier()).c_str());
@@ -5003,7 +5011,8 @@ Parse::goto_stat()
error_at(this->location(), "expected label for goto");
else
{
- Label* label = this->gogo_->add_label_reference(token->identifier());
+ Label* label = this->gogo_->add_label_reference(token->identifier(),
+ location, true);
Statement* s = Statement::make_goto_statement(label, location);
this->gogo_->add_statement(s);
this->advance_token();
Index: gcc/go/gofrontend/statements.cc
===================================================================
--- gcc/go/gofrontend/statements.cc (revision 179008)
+++ gcc/go/gofrontend/statements.cc (working copy)
@@ -2291,7 +2291,7 @@ Thunk_statement::build_thunk(Gogo* gogo,
Label* retaddr_label = NULL;
if (may_call_recover)
{
- retaddr_label = gogo->add_label_reference("retaddr");
+ retaddr_label = gogo->add_label_reference("retaddr", location, false);
Expression* arg = Expression::make_label_addr(retaddr_label, location);
Expression* call = Runtime::make_call(Runtime::SET_DEFER_RETADDR,
location, 1, arg);
Index: libgo/syscalls/exec.go
===================================================================
--- libgo/syscalls/exec.go (revision 178910)
+++ libgo/syscalls/exec.go (working copy)
@@ -231,6 +231,7 @@ var zeroSysProcAttr SysProcAttr
func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err int) {
var p [2]int
+ var n Ssize_t
var r1 int
var err1 uintptr
var wstatus WaitStatus
@@ -283,20 +284,14 @@ func forkExec(argv0 string, argv []strin
// Kick off child.
pid, err = forkAndExecInChild(argv0p, argvp, envvp, chroot, dir, attr, sys, p[1])
if err != 0 {
- error:
- if p[0] >= 0 {
- Close(p[0])
- Close(p[1])
- }
- ForkLock.Unlock()
- return 0, err
+ goto error
}
ForkLock.Unlock()
// Read child error status from pipe.
Close(p[1])
- n := libc_read(p[0], (*byte)(unsafe.Pointer(&err1)),
- Size_t(unsafe.Sizeof(err1)))
+ n = libc_read(p[0], (*byte)(unsafe.Pointer(&err1)),
+ Size_t(unsafe.Sizeof(err1)))
err = 0
if n < 0 {
err = GetErrno()
@@ -321,6 +316,14 @@ func forkExec(argv0 string, argv []strin
// Read got EOF, so pipe closed on exec, so exec succeeded.
return pid, 0
+
+error:
+ if p[0] >= 0 {
+ Close(p[0])
+ Close(p[1])
+ }
+ ForkLock.Unlock()
+ return 0, err
}
// Combination of fork and exec, careful to be thread safe.
Index: gcc/testsuite/go.test/test/fixedbugs/bug178.go
===================================================================
--- gcc/testsuite/go.test/test/fixedbugs/bug178.go (revision 178784)
+++ gcc/testsuite/go.test/test/fixedbugs/bug178.go (working copy)
@@ -14,6 +14,9 @@ L:
break L
}
panic("BUG: not reached - break")
+ if false {
+ goto L1
+ }
}
L2:
@@ -23,11 +26,8 @@ L2:
continue L2
}
panic("BUG: not reached - continue")
- }
- if false {
- goto L1
- }
- if false {
- goto L3
+ if false {
+ goto L3
+ }
}
}
Index: gcc/testsuite/go.test/test/fixedbugs/bug140.go
===================================================================
--- gcc/testsuite/go.test/test/fixedbugs/bug140.go (revision 178784)
+++ gcc/testsuite/go.test/test/fixedbugs/bug140.go (working copy)
@@ -10,14 +10,14 @@ func main() {
if true {
} else {
L1:
+ goto L1
}
if true {
} else {
+ goto L2
L2:
main()
}
- goto L1
- goto L2
}
/*
Index: gcc/testsuite/go.test/test/if.go
===================================================================
--- gcc/testsuite/go.test/test/if.go (revision 178784)
+++ gcc/testsuite/go.test/test/if.go (working copy)
@@ -53,25 +53,28 @@ func main() {
count = 0
if true {
count = count + 1
- } else
+ } else {
count = count - 1
+ }
assertequal(count, 1, "if else true")
count = 0
if false {
count = count + 1
- } else
+ } else {
count = count - 1
+ }
assertequal(count, -1, "if else false")
count = 0
- if t:=1; false {
+ if t := 1; false {
count = count + 1
_ = t
t := 7
_ = t
- } else
+ } else {
count = count - t
+ }
assertequal(count, -1, "if else false var")
count = 0
@@ -80,8 +83,9 @@ func main() {
count = count + 1
t := 7
_ = t
- } else
+ } else {
count = count - t
+ }
_ = t
assertequal(count, -1, "if else false var outside")
}
